update headless dev command

# Conflicts:
#	core/src/main/java/com/volmit/iris/core/commands/CommandDeveloper.java
#	core/src/main/java/com/volmit/iris/core/commands/CommandIris.java
#	core/src/main/java/com/volmit/iris/core/nms/v1X/NMSBinding1X.java
#	core/src/main/java/com/volmit/iris/core/tools/IrisPackBenchmarking.java
#	nms/v1_20_R1/src/main/java/com/volmit/iris/core/nms/v1_20_R1/NMSBinding.java
#	nms/v1_20_R2/src/main/java/com/volmit/iris/core/nms/v1_20_R2/NMSBinding.java
#	nms/v1_20_R3/src/main/java/com/volmit/iris/core/nms/v1_20_R3/NMSBinding.java
#	nms/v1_20_R4/src/main/java/com/volmit/iris/core/nms/v1_20_R4/NMSBinding.java
#	nms/v1_21_R1/src/main/java/com/volmit/iris/core/nms/v1_21_R1/NMSBinding.java
#	nms/v1_21_R2/src/main/java/com/volmit/iris/core/nms/v1_21_R2/NMSBinding.java
#	nms/v1_21_R3/src/main/java/com/volmit/iris/core/nms/v1_21_R3/NMSBinding.java

build.gradle

@@ -33,7 +33,7 @@ plugins {
 }
 
 
-version '3.6.4-1.20.1-1.21.4'
+version '3.6.5-1.20.1-1.21.4'
 
 // ADD YOURSELF AS A NEW LINE IF YOU WANT YOUR OWN BUILD TASK GENERATED
 // ======================== WINDOWS =============================
@@ -92,6 +92,11 @@ shadowJar {
     relocate 'net.kyori', 'com.volmit.iris.util.kyori'
     relocate 'org.bstats', 'com.volmit.util.metrics'
     archiveFileName.set("Iris-${project.version}.jar")
+
+    dependencies {
+        exclude(dependency("org.ow2.asm:asm:"))
+        exclude(dependency("org.jetbrains:"))
+    }
 }
 
 dependencies {

core/src/main/java/com/volmit/iris/Iris.java

@@ -459,15 +459,17 @@ public class Iris extends VolmitPlugin implements Listener {
         initialize("com.volmit.iris.core.service").forEach((i) -> services.put((Class<? extends IrisService>) i.getClass(), (IrisService) i));
         INMS.get();
         IO.delete(new File("iris"));
+        compat = IrisCompat.configured(getDataFile("compat.json"));
+        ServerConfigurator.configure();
+        new IrisContextInjector();
         IrisSafeguard.IrisSafeguardSystem();
         getSender().setTag(getTag());
-        compat = IrisCompat.configured(getDataFile("compat.json"));
+        IrisSafeguard.earlySplash();
         linkMultiverseCore = new MultiverseCoreLink();
         linkMythicMobs = new MythicMobsLink();
         configWatcher = new FileWatcher(getDataFile("settings.json"));
         services.values().forEach(IrisService::onEnable);
         services.values().forEach(this::registerListener);
-        registerListener(new IrisContextInjector());
         J.s(() -> {
             J.a(() -> PaperLib.suggestPaper(this));
             J.a(() -> IO.delete(getTemp()));

core/src/main/java/com/volmit/iris/core/ServerConfigurator.java

@@ -31,6 +31,7 @@ import com.volmit.iris.util.collection.KList;
 import com.volmit.iris.util.collection.KMap;
 import com.volmit.iris.util.collection.KSet;
 import com.volmit.iris.util.format.C;
+import com.volmit.iris.util.misc.ServerProperties;
 import com.volmit.iris.util.plugin.VolmitSender;
 import com.volmit.iris.util.scheduling.J;
 import lombok.Data;
@@ -97,6 +98,7 @@ public class ServerConfigurator {
         }
         KList<File> worlds = new KList<>();
         Bukkit.getServer().getWorlds().forEach(w -> worlds.add(new File(w.getWorldFolder(), "datapacks")));
+        if (worlds.isEmpty()) worlds.add(new File(Bukkit.getWorldContainer(), ServerProperties.LEVEL_NAME + "/datapacks"));
         return worlds;
     }
 

core/src/main/java/com/volmit/iris/core/commands/CommandDeveloper.java

@@ -22,11 +22,14 @@ import com.volmit.iris.Iris;
 import com.volmit.iris.core.ServerConfigurator;
 import com.volmit.iris.core.loader.IrisData;
 import com.volmit.iris.core.nms.datapack.DataVersion;
+import com.volmit.iris.core.pregenerator.PregenTask;
+import com.volmit.iris.core.pregenerator.methods.HeadlessPregenMethod;
 import com.volmit.iris.core.service.IrisEngineSVC;
 import com.volmit.iris.core.tools.IrisPackBenchmarking;
 import com.volmit.iris.core.tools.IrisToolbelt;
 import com.volmit.iris.engine.framework.Engine;
 import com.volmit.iris.engine.object.IrisDimension;
+import com.volmit.iris.engine.platform.PlatformChunkGenerator;
 import com.volmit.iris.util.decree.DecreeExecutor;
 import com.volmit.iris.util.decree.DecreeOrigin;
 import com.volmit.iris.util.decree.annotations.Decree;
@@ -36,6 +39,7 @@ import com.volmit.iris.util.format.Form;
 import com.volmit.iris.util.io.CountingDataInputStream;
 import com.volmit.iris.util.io.IO;
 import com.volmit.iris.util.mantle.TectonicPlate;
+import com.volmit.iris.util.math.Position2;
 import com.volmit.iris.util.nbt.mca.MCAFile;
 import com.volmit.iris.util.nbt.mca.MCAUtil;
 import com.volmit.iris.util.parallel.MultiBurst;
@@ -48,6 +52,7 @@ import org.apache.commons.lang.RandomStringUtils;
 import org.bukkit.Bukkit;
 import org.bukkit.Chunk;
 import org.bukkit.World;
+import org.bukkit.util.Vector;
 
 import java.io.*;
 import java.net.InetAddress;
@@ -140,12 +145,16 @@ public class CommandDeveloper implements DecreeExecutor {
     public void packBenchmark(
             @Param(description = "The pack to bench", aliases = {"pack"}, defaultValue = "overworld")
             IrisDimension dimension,
-            @Param(description = "Radius in regions", defaultValue = "5")
+            @Param(description = "Diameter in regions", defaultValue = "2048")
-            int radius,
+            int diameter,
+            @Param(description = "Headless", defaultValue = "true")
+            boolean headless,
             @Param(description = "Open GUI while benchmarking", defaultValue = "false")
             boolean gui
     ) {
-        new IrisPackBenchmarking(dimension, radius, gui);
+        int rb = diameter << 9;
+        Iris.info("Benchmarking pack " + dimension.getName() + " with diameter: " + rb + "(" + diameter + ")");
+        new IrisPackBenchmarking(dimension, diameter, headless, gui);
     }
 
     @Decree(description = "Upgrade to another Minecraft version")
@@ -213,6 +222,42 @@ public class CommandDeveloper implements DecreeExecutor {
         sender.sendMessage(C.RED + "Failed to load " + failed.get() + " of " + keys.length + " objects");
     }
 
+    @Decree(description = "Pregenerate a world")
+    public void headless(
+            @Param(description = "The radius of the pregen in blocks", aliases = "size")
+            int radius,
+            @Param(description = "The world to pregen", contextual = true)
+            World world,
+            @Param(aliases = "middle", description = "The center location of the pregen. Use \"me\" for your current location", defaultValue = "0,0")
+            Vector center
+    ) {
+        try {
+            var engine = Optional.ofNullable(IrisToolbelt.access(world))
+                    .map(PlatformChunkGenerator::getEngine)
+                    .orElse(null);
+
+            if (engine == null) {
+                sender().sendMessage(C.RED + "The engine access for this world is null!");
+                sender().sendMessage(C.RED + "Please make sure the world is loaded & the engine is initialized. Generate a new chunk, for example.");
+            }
+            radius = Math.max(radius, 1024);
+            IrisToolbelt.pregenerate(PregenTask
+                    .builder()
+                    .center(new Position2(center.getBlockX(), center.getBlockZ()))
+                    .gui(true)
+                    .radiusX(radius)
+                    .radiusZ(radius)
+                    .build(), new HeadlessPregenMethod(engine), engine);
+            String msg = C.GREEN + "Headless Pregen started in " + C.GOLD + world.getName() + C.GREEN + " of " + C.GOLD + (radius * 2) + C.GREEN + " by " + C.GOLD + (radius * 2) + C.GREEN + " blocks from " + C.GOLD + center.getX() + "," + center.getZ();
+            sender().sendMessage(msg);
+            Iris.info(msg);
+        } catch (Throwable e) {
+            sender().sendMessage(C.RED + "Epic fail. See console.");
+            Iris.reportError(e);
+            e.printStackTrace();
+        }
+    }
+
     @Decree(description = "Test", aliases = {"ip"})
     public void network() {
         try {

core/src/main/java/com/volmit/iris/core/commands/CommandPregen.java

@@ -19,9 +19,7 @@
 package com.volmit.iris.core.commands;
 
 import com.volmit.iris.Iris;
-import com.volmit.iris.core.IrisSettings;
 import com.volmit.iris.core.gui.PregeneratorJob;
-import com.volmit.iris.core.pregenerator.LazyPregenerator;
 import com.volmit.iris.core.pregenerator.PregenTask;
 import com.volmit.iris.core.tools.IrisToolbelt;
 import com.volmit.iris.util.decree.DecreeExecutor;
@@ -29,12 +27,9 @@ import com.volmit.iris.util.decree.annotations.Decree;
 import com.volmit.iris.util.decree.annotations.Param;
 import com.volmit.iris.util.format.C;
 import com.volmit.iris.util.math.Position2;
-import org.bukkit.Bukkit;
 import org.bukkit.World;
 import org.bukkit.util.Vector;
 
-import java.io.File;
-
 @Decree(name = "pregen", aliases = "pregenerate", description = "Pregenerate your Iris worlds!")
 public class CommandPregen implements DecreeExecutor {
     @Decree(description = "Pregenerate a world")
@@ -52,13 +47,12 @@ public class CommandPregen implements DecreeExecutor {
                 sender().sendMessage(C.RED + "Please make sure the world is loaded & the engine is initialized. Generate a new chunk, for example.");
             }
             radius = Math.max(radius, 1024);
-            int w = (radius >> 9 + 1) * 2;
             IrisToolbelt.pregenerate(PregenTask
                     .builder()
-                    .center(new Position2(center.getBlockX() >> 9, center.getBlockZ() >> 9))
+                    .center(new Position2(center.getBlockX(), center.getBlockZ()))
                     .gui(true)
-                    .width(w)
+                    .radiusX(radius)
-                    .height(w)
+                    .radiusZ(radius)
                     .build(), world);
             String msg = C.GREEN + "Pregen started in " + C.GOLD + world.getName() + C.GREEN + " of " + C.GOLD + (radius * 2) + C.GREEN + " by " + C.GOLD + (radius * 2) + C.GREEN + " blocks from " + C.GOLD + center.getX() + "," + center.getZ();
             sender().sendMessage(msg);

core/src/main/java/com/volmit/iris/core/gui/PregeneratorJob.java

@@ -24,7 +24,6 @@ import com.volmit.iris.core.pregenerator.IrisPregenerator;
 import com.volmit.iris.core.pregenerator.PregenListener;
 import com.volmit.iris.core.pregenerator.PregenTask;
 import com.volmit.iris.core.pregenerator.PregeneratorMethod;
-import com.volmit.iris.core.tools.IrisPackBenchmarking;
 import com.volmit.iris.engine.framework.Engine;
 import com.volmit.iris.util.collection.KList;
 import com.volmit.iris.util.format.Form;
@@ -45,8 +44,6 @@ import java.util.concurrent.TimeUnit;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.function.Consumer;
 
-import static com.volmit.iris.core.tools.IrisPackBenchmarking.benchmarkInProgress;
-
 public class PregeneratorJob implements PregenListener {
     private static final Color COLOR_EXISTS = parseColor("#4d7d5b");
     private static final Color COLOR_BLACK = parseColor("#4d7d5b");
@@ -81,12 +78,12 @@ public class PregeneratorJob implements PregenListener {
         this.task = task;
         this.pregenerator = new IrisPregenerator(task, method, this);
         max = new Position2(0, 0);
-        min = new Position2(0, 0);
+        min = new Position2(Integer.MAX_VALUE, Integer.MAX_VALUE);
-        task.iterateRegions((xx, zz) -> {
+        task.iterateAllChunks((xx, zz) -> {
-            min.setX(Math.min(xx << 5, min.getX()));
+            min.setX(Math.min(xx, min.getX()));
-            min.setZ(Math.min(zz << 5, min.getZ()));
+            min.setZ(Math.min(zz, min.getZ()));
-            max.setX(Math.max((xx << 5) + 31, max.getX()));
+            max.setX(Math.max(xx, max.getX()));
-            max.setZ(Math.max((zz << 5) + 31, max.getZ()));
+            max.setZ(Math.max(zz, max.getZ()));
         });
 
         if (IrisSettings.get().getGui().isUseServerLaunchedGuis() && task.isGui()) {
@@ -162,7 +159,7 @@ public class PregeneratorJob implements PregenListener {
     }
 
     public void drawRegion(int x, int z, Color color) {
-        J.a(() -> PregenTask.iterateRegion(x, z, (xx, zz) -> {
+        J.a(() -> task.iterateChunks(x, z, (xx, zz) -> {
             draw(xx, zz, color);
             J.sleep(3);
         }));

core/src/main/java/com/volmit/iris/core/nms/INMS.java

@@ -37,7 +37,7 @@ public class INMS {
             "1.21.4", "v1_21_R3"
     );
     private static final List<Version> PACKS = List.of(
-            new Version(21, 4, "31010"),
+            new Version(21, 4, "31020"),
             new Version(21, 2, "31000"),
             new Version(20, 1, "3910")
     );

core/src/main/java/com/volmit/iris/core/nms/INMSBinding.java

@@ -22,6 +22,7 @@ import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
 import com.volmit.iris.core.nms.container.Pair;
 import com.volmit.iris.core.nms.datapack.DataVersion;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
 import com.volmit.iris.engine.framework.Engine;
 import com.volmit.iris.util.collection.KList;
 import com.volmit.iris.util.collection.KMap;
@@ -32,15 +33,12 @@ import com.volmit.iris.util.nbt.mca.palette.MCAPaletteAccess;
 import com.volmit.iris.util.nbt.tag.CompoundTag;
 import org.bukkit.*;
 import org.bukkit.block.Biome;
-import org.bukkit.entity.Dolphin;
 import org.bukkit.entity.Entity;
 import org.bukkit.entity.EntityType;
 import org.bukkit.event.entity.CreatureSpawnEvent;
 import org.bukkit.generator.ChunkGenerator;
-import org.bukkit.generator.structure.Structure;
 import org.bukkit.inventory.ItemStack;
 
-import java.awt.*;
 import java.awt.Color;
 
 public interface INMSBinding {
@@ -93,6 +91,9 @@ public interface INMSBinding {
     MCABiomeContainer newBiomeContainer(int min, int max);
 
     default World createWorld(WorldCreator c) {
+        if (missingDimensionTypes(true, true, true))
+            throw new IllegalStateException("Missing dimenstion types to create world");
+
         try (var ignored = injectLevelStems()) {
             return c.createWorld();
         }
@@ -128,13 +129,13 @@ public interface INMSBinding {
         return 441;
     }
 
+    IRegionStorage createRegionStorage(Engine engine);
+
     KList<String> getStructureKeys();
 
-    default AutoClosing injectLevelStems() {
+    AutoClosing injectLevelStems();
-        return new AutoClosing(() -> {});
-    }
 
-    default Pair<Integer, AutoClosing> injectUncached(boolean overworld, boolean nether, boolean end) {
+    Pair<Integer, AutoClosing> injectUncached(boolean overworld, boolean nether, boolean end);
-        return new Pair<>(0, injectLevelStems());
+
-    }
+    boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end);
 }

core/src/main/java/com/volmit/iris/core/nms/headless/IRegion.java

@@ -0,0 +1,17 @@
+package com.volmit.iris.core.nms.headless;
+
+import com.volmit.iris.util.documentation.ChunkCoordinates;
+import lombok.NonNull;
+
+import java.io.IOException;
+
+public interface IRegion extends AutoCloseable {
+
+    @ChunkCoordinates
+    boolean exists(int x, int z);
+
+    void write(@NonNull SerializableChunk chunk) throws IOException;
+
+    @Override
+    void close();
+}

core/src/main/java/com/volmit/iris/core/nms/headless/IRegionStorage.java

@@ -0,0 +1,27 @@
+package com.volmit.iris.core.nms.headless;
+
+import com.volmit.iris.util.context.ChunkContext;
+import com.volmit.iris.util.documentation.ChunkCoordinates;
+import com.volmit.iris.util.documentation.RegionCoordinates;
+import lombok.NonNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.io.IOException;
+
+public interface IRegionStorage {
+
+    @ChunkCoordinates
+    boolean exists(int x, int z);
+
+    @Nullable
+    @RegionCoordinates
+    IRegion getRegion(int x, int z, boolean existingOnly) throws IOException;
+
+    @NonNull
+    @ChunkCoordinates
+    SerializableChunk createChunk(int x, int z);
+
+    void fillBiomes(@NonNull SerializableChunk chunk, @Nullable ChunkContext ctx);
+
+    void close();
+}

core/src/main/java/com/volmit/iris/core/nms/headless/SerializableChunk.java

@@ -0,0 +1,12 @@
+package com.volmit.iris.core.nms.headless;
+
+import com.volmit.iris.engine.data.chunk.TerrainChunk;
+import com.volmit.iris.util.math.Position2;
+
+public interface SerializableChunk extends TerrainChunk {
+    Position2 getPos();
+
+    Object serialize();
+
+    void mark();
+}

core/src/main/java/com/volmit/iris/core/nms/v1X/NMSBinding1X.java

@@ -20,7 +20,10 @@ package com.volmit.iris.core.nms.v1X;
 
 import com.volmit.iris.Iris;
 import com.volmit.iris.core.nms.INMSBinding;
+import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
+import com.volmit.iris.core.nms.container.Pair;
 import com.volmit.iris.engine.framework.Engine;
 import com.volmit.iris.util.collection.KList;
 import com.volmit.iris.util.collection.KMap;
@@ -109,6 +112,11 @@ public class NMSBinding1X implements INMSBinding {
         return Color.GREEN;
     }
 
+    @Override
+    public IRegionStorage createRegionStorage(Engine engine) {
+        return null;
+    }
+
     @Override
     public KList<String> getStructureKeys() {
         var list = StreamSupport.stream(Registry.STRUCTURE.spliterator(), false)
@@ -118,6 +126,21 @@ public class NMSBinding1X implements INMSBinding {
         return new KList<>(list);
     }
 
+    @Override
+    public AutoClosing injectLevelStems() {
+        return new AutoClosing(() -> {});
+    }
+
+    @Override
+    public Pair<Integer, AutoClosing> injectUncached(boolean overworld, boolean nether, boolean end) {
+        return new Pair<>(0, new AutoClosing(() -> {}));
+    }
+
+    @Override
+    public boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end) {
+        return false;
+    }
+
     @Override
     public CompoundTag serializeEntity(Entity location) {
         return null;

core/src/main/java/com/volmit/iris/core/pregenerator/ChunkUpdater.java

@@ -165,8 +165,11 @@ public class ChunkUpdater {
             if (rX < dimensions.min.getX() || rX > dimensions.max.getX() || rZ < dimensions.min.getZ() || rZ > dimensions.max.getZ()) {
                 return;
             }
+            if (!new File(world.getWorldFolder(), "region" + File.separator + rX + "." + rZ + ".mca").exists()) {
+                return;
+            }
 
-            PregenTask.iterateRegion(rX, rZ, (x, z) -> {
+            task.iterateChunks(rX, rZ, (x, z) -> {
                 while (paused.get() && !cancelled.get()) {
                     J.sleep(50);
                 }
@@ -348,8 +351,8 @@ public class ChunkUpdater {
         int width = maxZ - minZ + 1;
 
         return new Dimensions(new Position2(minX, minZ), new Position2(maxX, maxZ), height * width, PregenTask.builder()
-                .width((int) Math.ceil(width / 2d))
+                .radiusZ((int) Math.ceil(width / 2d * 512))
-                .height((int) Math.ceil(height / 2d))
+                .radiusX((int) Math.ceil(height / 2d * 512))
                 .center(new Position2(oX, oZ))
                 .build());
     }

core/src/main/java/com/volmit/iris/core/pregenerator/EmptyListener.java

@@ -0,0 +1,80 @@
+package com.volmit.iris.core.pregenerator;
+
+public class EmptyListener implements PregenListener {
+    public static PregenListener INSTANCE = new EmptyListener();
+
+    @Override
+    public void onTick(double chunksPerSecond, double chunksPerMinute, double regionsPerMinute, double percent, int generated, int totalChunks, int chunksRemaining, long eta, long elapsed, String method) {
+
+    }
+
+    @Override
+    public void onChunkGenerating(int x, int z) {
+
+    }
+
+    @Override
+    public void onChunkGenerated(int x, int z) {
+
+    }
+
+    @Override
+    public void onRegionGenerated(int x, int z) {
+
+    }
+
+    @Override
+    public void onRegionGenerating(int x, int z) {
+
+    }
+
+    @Override
+    public void onChunkCleaned(int x, int z) {
+
+    }
+
+    @Override
+    public void onRegionSkipped(int x, int z) {
+
+    }
+
+    @Override
+    public void onNetworkStarted(int x, int z) {
+
+    }
+
+    @Override
+    public void onNetworkFailed(int x, int z) {
+
+    }
+
+    @Override
+    public void onNetworkReclaim(int revert) {
+
+    }
+
+    @Override
+    public void onNetworkGeneratedChunk(int x, int z) {
+
+    }
+
+    @Override
+    public void onNetworkDownloaded(int x, int z) {
+
+    }
+
+    @Override
+    public void onClose() {
+
+    }
+
+    @Override
+    public void onSaving() {
+
+    }
+
+    @Override
+    public void onChunkExistsInRegionGen(int x, int z) {
+
+    }
+}

core/src/main/java/com/volmit/iris/core/pregenerator/IrisPregenerator.java

@@ -19,7 +19,6 @@
 package com.volmit.iris.core.pregenerator;
 
 import com.volmit.iris.Iris;
-import com.volmit.iris.core.pack.IrisPack;
 import com.volmit.iris.core.tools.IrisPackBenchmarking;
 import com.volmit.iris.util.collection.KList;
 import com.volmit.iris.util.collection.KSet;
@@ -83,7 +82,7 @@ public class IrisPregenerator {
         generatedLast = new AtomicInteger(0);
         generatedLastMinute = new AtomicInteger(0);
         totalChunks = new AtomicInteger(0);
-        task.iterateRegions((_a, _b) -> totalChunks.addAndGet(1024));
+        task.iterateAllChunks((_a, _b) -> totalChunks.incrementAndGet());
         startTime = new AtomicLong(M.ms());
         ticker = new Looper() {
             @Override
@@ -194,7 +193,7 @@ public class IrisPregenerator {
         } else if (!regions) {
             hit = true;
             listener.onRegionGenerating(x, z);
-            PregenTask.iterateRegion(x, z, (xx, zz) -> {
+            task.iterateChunks(x, z, (xx, zz) -> {
                 while (paused.get() && !shutdown.get()) {
                     J.sleep(50);
                 }

core/src/main/java/com/volmit/iris/core/pregenerator/PregenTask.java

@@ -32,17 +32,26 @@ import java.util.Comparator;
 @Data
 public class PregenTask {
     private static final Position2 ZERO = new Position2(0, 0);
-    private static final KList<Position2> ORDER_CENTER = computeChunkOrder();
     private static final KMap<Position2, KList<Position2>> ORDERS = new KMap<>();
 
     @Builder.Default
-    private boolean gui = false;
+    private final boolean gui = false;
     @Builder.Default
-    private Position2 center = new Position2(0, 0);
+    private final Position2 center = new Position2(0, 0);
     @Builder.Default
-    private int width = 1;
+    private final int radiusX = 1;
     @Builder.Default
-    private int height = 1;
+    private final int radiusZ = 1;
+
+    private final Bounds bounds = new Bounds();
+
+    protected PregenTask(boolean gui, Position2 center, int radiusX, int radiusZ) {
+        this.gui = gui;
+        this.center = new ProxiedPos(center);
+        this.radiusX = radiusX;
+        this.radiusZ = radiusZ;
+        bounds.update();
+    }
 
     public static void iterateRegion(int xr, int zr, Spiraled s, Position2 pull) {
         for (Position2 i : ORDERS.computeIfAbsent(pull, PregenTask::computeOrder)) {
@@ -70,29 +79,72 @@ public class PregenTask {
         return p;
     }
 
-    private static KList<Position2> computeChunkOrder() {
+    public void iterateRegions(Spiraled s) {
-        Position2 center = new Position2(15, 15);
+        var bound = bounds.region();
-        KList<Position2> p = new KList<>();
+        new Spiraler(bound.sizeX, bound.sizeZ, ((x, z) -> {
-        new Spiraler(33, 33, (x, z) -> {
+            if (bound.check(x, z)) s.on(x, z);
-            int xx = x + 15;
+        })).setOffset(center.getX() >> 9, center.getZ() >> 9).drain();
-            int zz = z + 15;
-            if (xx < 0 || xx > 31 || zz < 0 || zz > 31) {
-                return;
-            }
-
-            p.add(new Position2(xx, zz));
-        }).drain();
-        p.sort(Comparator.comparing((i) -> i.distance(center)));
-        return p;
     }
 
-    public void iterateRegions(Spiraled s) {
+    public void iterateChunks(int rX, int rZ, Spiraled s) {
-        new Spiraler(getWidth() * 2, getHeight() * 2, s)
+        var bound = bounds.chunk();
-                .setOffset(center.getX(), center.getZ()).drain();
+        iterateRegion(rX, rZ, ((x, z) -> {
+            if (bound.check(x, z)) s.on(x, z);
+        }));
     }
 
     public void iterateAllChunks(Spiraled s) {
-        new Spiraler(getWidth() * 2, getHeight() * 2, (x, z) -> iterateRegion(x, z, s))
+        iterateRegions(((rX, rZ) -> iterateChunks(rX, rZ, s)));
-                .setOffset(center.getX(), center.getZ()).drain();
+    }
+
+    private class Bounds {
+        private Bound chunk = null;
+        private Bound region = null;
+
+        public void update() {
+            int maxX = center.getX() + radiusX;
+            int maxZ = center.getZ() + radiusZ;
+            int minX = center.getX() - radiusX;
+            int minZ = center.getZ() - radiusZ;
+
+            chunk = new Bound(minX >> 4, minZ >> 4, Math.ceilDiv(maxX, 16), Math.ceilDiv(maxZ, 16));
+            region = new Bound(minX >> 9, minZ >> 9, Math.ceilDiv(maxX, 512), Math.ceilDiv(maxZ, 512));
+        }
+
+        public Bound chunk() {
+            if (chunk == null) update();
+            return chunk;
+        }
+
+        public Bound region() {
+            if (region == null) update();
+            return region;
+        }
+    }
+
+    private record Bound(int minX, int maxX, int minZ, int maxZ, int sizeX, int sizeZ) {
+        private Bound(int minX, int minZ, int maxX, int maxZ) {
+            this(minX, maxX, minZ, maxZ, maxZ - minZ + 1, maxZ - minZ + 1);
+        }
+
+        boolean check(int x, int z) {
+            return x >= minX && x <= maxX && z >= minZ && z <= maxZ;
+        }
+    }
+
+    private static class ProxiedPos extends Position2 {
+        public ProxiedPos(Position2 p) {
+            super(p.getX(), p.getZ());
+        }
+
+        @Override
+        public void setX(int x) {
+            throw new IllegalStateException("This Position2 may not be modified");
+        }
+
+        @Override
+        public void setZ(int z) {
+            throw new IllegalStateException("This Position2 may not be modified");
+        }
     }
 }

core/src/main/java/com/volmit/iris/core/pregenerator/methods/HeadlessPregenMethod.java

@@ -0,0 +1,112 @@
+/*
+ *  Iris is a World Generator for Minecraft Bukkit Servers
+ *  Copyright (c) 2024 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.volmit.iris.core.pregenerator.methods;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.IrisSettings;
+import com.volmit.iris.core.pregenerator.PregenListener;
+import com.volmit.iris.core.pregenerator.PregeneratorMethod;
+import com.volmit.iris.engine.framework.Engine;
+import com.volmit.iris.engine.object.IrisHeadless;
+import com.volmit.iris.util.mantle.Mantle;
+import com.volmit.iris.util.parallel.MultiBurst;
+
+import java.io.IOException;
+import java.util.concurrent.Semaphore;
+
+public class HeadlessPregenMethod implements PregeneratorMethod {
+    private final Engine engine;
+    private final IrisHeadless headless;
+    private final Semaphore semaphore;
+    private final int max;
+    private final MultiBurst burst;
+
+    public HeadlessPregenMethod(Engine engine) {
+        this(engine, IrisSettings.getThreadCount(IrisSettings.get().getConcurrency().getParallelism()));
+    }
+
+    public HeadlessPregenMethod(Engine engine, int threads) {
+        this.max = Math.max(threads, 4);
+        this.engine = engine;
+        this.headless = new IrisHeadless(engine);
+        burst = new MultiBurst("HeadlessPregen", 8);
+        this.semaphore = new Semaphore(max);
+    }
+
+    @Override
+    public void init() {
+    }
+
+    @Override
+    public void close() {
+        try {
+            semaphore.acquire(max);
+        } catch (InterruptedException ignored) {
+        }
+        try {
+            headless.close();
+        } catch (IOException e) {
+            Iris.error("Failed to close headless");
+            e.printStackTrace();
+        }
+        burst.close();
+    }
+
+    @Override
+    public void save() {
+    }
+
+    @Override
+    public boolean supportsRegions(int x, int z, PregenListener listener) {
+        return false;
+    }
+
+    @Override
+    public String getMethod(int x, int z) {
+        return "Headless";
+    }
+
+    @Override
+    public void generateRegion(int x, int z, PregenListener listener) {
+    }
+
+    @Override
+    public void generateChunk(int x, int z, PregenListener listener) {
+        try {
+            semaphore.acquire();
+        } catch (InterruptedException ignored) {
+            return;
+        }
+
+        burst.complete(() -> {
+            try {
+                listener.onChunkGenerating(x, z);
+                headless.generateChunk(x, z);
+                listener.onChunkGenerated(x, z);
+            } finally {
+                semaphore.release();
+            }
+        });
+    }
+
+    @Override
+    public Mantle getMantle() {
+        return engine.getMantle().getMantle();
+    }
+}

core/src/main/java/com/volmit/iris/core/safeguard/IrisSafeguard.java

@@ -1,6 +1,7 @@
 package com.volmit.iris.core.safeguard;
 
 import com.volmit.iris.Iris;
+import com.volmit.iris.core.IrisSettings;
 
 public class IrisSafeguard {
     public static boolean unstablemode = false;
@@ -11,5 +12,13 @@ public class IrisSafeguard {
         Iris.info("Enabled Iris SafeGuard");
         ServerBootSFG.BootCheck();
     }
+
+    public static void earlySplash() {
+        if (ServerBootSFG.safeguardPassed || IrisSettings.get().getGeneral().DoomsdayAnnihilationSelfDestructMode)
+            return;
+
+        Iris.instance.splash();
+        UtilsSFG.splash();
+    }
 }
 

core/src/main/java/com/volmit/iris/core/safeguard/ServerBootSFG.java

@@ -3,6 +3,7 @@ package com.volmit.iris.core.safeguard;
 import com.volmit.iris.Iris;
 import com.volmit.iris.core.nms.INMS;
 import com.volmit.iris.core.nms.v1X.NMSBinding1X;
+import com.volmit.iris.engine.object.IrisContextInjector;
 import org.bukkit.Bukkit;
 import org.bukkit.plugin.Plugin;
 import org.bukkit.plugin.PluginManager;
@@ -29,6 +30,7 @@ public class ServerBootSFG {
     public static boolean isJRE = false;
     public static boolean hasPrivileges = true;
     public static boolean unsuportedversion = false;
+    public static boolean missingDimensionTypes = false;
     protected static boolean safeguardPassed;
     public static boolean passedserversoftware = true;
     protected static int count;
@@ -110,6 +112,12 @@ public class ServerBootSFG {
             severityMedium++;
         }
 
+        if (IrisContextInjector.isMissingDimensionTypes()) {
+            missingDimensionTypes = true;
+            joiner.add("Missing Dimension Types");
+            severityHigh++;
+        }
+
         allIncompatibilities = joiner.toString();
 
         safeguardPassed = (severityHigh == 0 && severityMedium == 0 && severityLow == 0);

core/src/main/java/com/volmit/iris/core/safeguard/UtilsSFG.java

@@ -39,6 +39,11 @@ public class UtilsSFG {
                 Iris.safeguard(C.RED + "Server Version");
                 Iris.safeguard(C.RED + "- Iris only supports 1.20.1 > 1.21.4");
             }
+            if (ServerBootSFG.missingDimensionTypes) {
+                Iris.safeguard(C.RED + "Dimension Types");
+                Iris.safeguard(C.RED + "- Required Iris dimension types were not loaded.");
+                Iris.safeguard(C.RED + "- If this still happens after a restart please contact support.");
+            }
             if (!ServerBootSFG.passedserversoftware) {
                 Iris.safeguard(C.YELLOW + "Unsupported Server Software");
                 Iris.safeguard(C.YELLOW + "- Please consider using Paper or Purpur instead.");

core/src/main/java/com/volmit/iris/core/tools/IrisCreator.java

@@ -84,6 +84,11 @@ public class IrisCreator {
      * Benchmark mode
      */
     private boolean benchmark = false;
+    /**
+     * Radius of chunks to pregenerate in the headless mode
+     * if set to -1, headless mode is disabled
+     */
+    private int headlessRadius = 10;
 
     public static boolean removeFromBukkitYml(String name) throws IOException {
         YamlConfiguration yml = YamlConfiguration.loadConfiguration(BUKKIT_YML);
@@ -127,7 +132,6 @@ public class IrisCreator {
             Iris.service(StudioSVC.class).installIntoWorld(sender, d.getLoadKey(), new File(Bukkit.getWorldContainer(), name()));
         }
 
-        PlatformChunkGenerator access;
         AtomicReference<World> world = new AtomicReference<>();
         AtomicDouble pp = new AtomicDouble(0);
         O<Boolean> done = new O<>();
@@ -140,30 +144,56 @@ public class IrisCreator {
                 .create();
         ServerConfigurator.installDataPacks(false);
 
-        access = (PlatformChunkGenerator) wc.generator();
+        PlatformChunkGenerator access = (PlatformChunkGenerator) wc.generator();
-        PlatformChunkGenerator finalAccess1 = access;
+        if (access == null) {
+            throw new IrisException("Access is null. Something bad happened.");
+        }
 
-        J.a(() ->
+        if (headlessRadius > 0 && !benchmark) {
-        {
+            AtomicBoolean failed = new AtomicBoolean(false);
-            Supplier<Integer> g = () -> {
+            J.a(() -> {
-                if (finalAccess1 == null || finalAccess1.getEngine() == null) {
+                int generated = access.getGenerated();
-                    return 0;
+                double total = Math.pow(headlessRadius * 2 + 1, 2);
+
+                while (generated < total) {
+                    if (failed.get()) return;
+
+                    double v = (double) generated / total;
+                    if (sender.isPlayer()) {
+                        sender.sendProgress(v, "Generating headless chunks");
+                        J.sleep(16);
+                    } else {
+                        sender.sendMessage(C.WHITE + "Generating headless chunks " + Form.pc(v) + ((C.GRAY + " (" + ((int) total - generated) + " Left)")));
+                        J.sleep(1000);
+                    }
+                    generated = access.getGenerated();
                 }
-                return finalAccess1.getEngine().getGenerated();
+            });
-            };
-            if(!benchmark) {
-                if (finalAccess1 == null) return;
-                int req = finalAccess1.getSpawnChunks().join();
 
-                while (g.get() < req) {
+            try {
-                    double v = (double) g.get() / (double) req;
+                access.prepareSpawnChunks(seed, headlessRadius);
+            } catch (Throwable e) {
+                Iris.error("Failed to prepare spawn chunks for " + name);
+                e.printStackTrace();
+                failed.set(true);
+            }
+        }
+
+        J.a(() -> {
+            if(!benchmark) {
+                int req = access.getSpawnChunks().join();
+
+                int generated = access.getGenerated();
+                while (generated < req) {
+                    double v = (double) generated / (double) req;
                     if (sender.isPlayer()) {
                         sender.sendProgress(v, "Generating");
                         J.sleep(16);
                     } else {
-                        sender.sendMessage(C.WHITE + "Generating " + Form.pc(v) + ((C.GRAY + " (" + (req - g.get()) + " Left)")));
+                        sender.sendMessage(C.WHITE + "Generating " + Form.pc(v) + ((C.GRAY + " (" + (req - generated) + " Left)")));
                         J.sleep(1000);
                     }
+                    generated = access.getGenerated();
                 }
             }
         });

core/src/main/java/com/volmit/iris/core/tools/IrisPackBenchmarking.java

@@ -2,13 +2,22 @@ package com.volmit.iris.core.tools;
 
 
 import com.volmit.iris.Iris;
+import com.volmit.iris.core.IrisSettings;
+import com.volmit.iris.core.loader.IrisData;
 import com.volmit.iris.core.pregenerator.PregenTask;
+import com.volmit.iris.core.pregenerator.methods.HeadlessPregenMethod;
+import com.volmit.iris.core.pregenerator.methods.HybridPregenMethod;
+import com.volmit.iris.core.service.StudioSVC;
+import com.volmit.iris.engine.IrisEngine;
 import com.volmit.iris.engine.framework.Engine;
+import com.volmit.iris.engine.framework.EngineTarget;
 import com.volmit.iris.engine.object.IrisDimension;
+import com.volmit.iris.engine.object.IrisWorld;
 import com.volmit.iris.util.collection.KList;
 import com.volmit.iris.util.collection.KMap;
 import com.volmit.iris.util.exceptions.IrisException;
 import com.volmit.iris.util.format.Form;
+import com.volmit.iris.util.io.IO;
 import com.volmit.iris.util.scheduling.J;
 import com.volmit.iris.util.scheduling.PrecisionStopwatch;
 import lombok.Getter;
@@ -17,11 +26,6 @@ import org.bukkit.Bukkit;
 import java.io.File;
 import java.io.FileWriter;
 import java.io.IOException;
-import java.nio.file.FileVisitResult;
-import java.nio.file.Files;
-import java.nio.file.Path;
-import java.nio.file.SimpleFileVisitor;
-import java.nio.file.attribute.BasicFileAttributes;
 import java.time.Clock;
 import java.time.LocalDateTime;
 import java.util.Collections;
@@ -33,13 +37,16 @@ public class IrisPackBenchmarking {
     public static boolean benchmarkInProgress = false;
     private final PrecisionStopwatch stopwatch = new PrecisionStopwatch();
     private final IrisDimension dimension;
-    private final int radius;
+    private final int diameter;
     private final boolean gui;
+    private final boolean headless;
+    private transient Engine engine;
 
-    public IrisPackBenchmarking(IrisDimension dimension, int radius, boolean gui) {
+    public IrisPackBenchmarking(IrisDimension dimension, int diameter, boolean headless, boolean gui) {
         instance = this;
         this.dimension = dimension;
-        this.radius = radius;
+        this.diameter = diameter;
+        this.headless = headless;
         this.gui = gui;
         runBenchmark();
     }
@@ -50,12 +57,9 @@ public class IrisPackBenchmarking {
                 .start(() -> {
                     Iris.info("Setting up benchmark environment ");
                     benchmarkInProgress = true;
-                    File file = new File("benchmark");
+                    IO.delete(new File(Bukkit.getWorldContainer(), "benchmark"));
-                    if (file.exists()) {
-                        deleteDirectory(file.toPath());
-                    }
                     createBenchmark();
-                    while (!IrisToolbelt.isIrisWorld(Bukkit.getWorld("benchmark"))) {
+                    while (!headless && !IrisToolbelt.isIrisWorld(Bukkit.getWorld("benchmark"))) {
                         J.sleep(1000);
                         Iris.debug("Iris PackBenchmark: Waiting...");
                     }
@@ -73,7 +77,6 @@ public class IrisPackBenchmarking {
     public void finishedBenchmark(KList<Integer> cps) {
         try {
             String time = Form.duration(stopwatch.getMillis());
-            Engine engine = IrisToolbelt.access(Bukkit.getWorld("benchmark")).getEngine();
             Iris.info("-----------------");
             Iris.info("Results:");
             Iris.info("- Total time: " + time);
@@ -114,12 +117,16 @@ public class IrisPackBenchmarking {
                 e.printStackTrace();
             }
 
-            J.s(() -> {
+            if (headless) {
-                var world = Bukkit.getWorld("benchmark");
+                engine.close();
-                if (world == null) return;
+            } else {
-                IrisToolbelt.evacuate(world);
+                J.s(() -> {
-                Bukkit.unloadWorld(world, true);
+                    var world = Bukkit.getWorld("benchmark");
-            });
+                    if (world == null) return;
+                    IrisToolbelt.evacuate(world);
+                    Bukkit.unloadWorld(world, true);
+                });
+            }
 
             stopwatch.end();
         } catch (Exception e) {
@@ -130,13 +137,34 @@ public class IrisPackBenchmarking {
 
     private void createBenchmark() {
         try {
-            IrisToolbelt.createWorld()
+            if (headless) {
+                Iris.info("Using headless benchmark!");
+                IrisWorld world = IrisWorld.builder()
+                        .name("benchmark")
+                        .minHeight(dimension.getMinHeight())
+                        .maxHeight(dimension.getMaxHeight())
+                        .seed(1337)
+                        .worldFolder(new File(Bukkit.getWorldContainer(), "benchmark"))
+                        .environment(dimension.getEnvironment())
+                        .build();
+                Iris.service(StudioSVC.class).installIntoWorld(
+                        Iris.getSender(),
+                        dimension.getLoadKey(),
+                        world.worldFolder());
+                var data = IrisData.get(new File(world.worldFolder(), "iris/pack"));
+                var dim = data.getDimensionLoader().load(dimension.getLoadKey());
+                engine = new IrisEngine(new EngineTarget(world, dim, data), false);
+                return;
+            }
+
+            engine = IrisToolbelt.access(IrisToolbelt.createWorld()
                     .dimension(dimension.getLoadKey())
                     .name("benchmark")
                     .seed(1337)
                     .studio(false)
                     .benchmark(true)
-                    .create();
+                    .create())
+                    .getEngine();
         } catch (IrisException e) {
             throw new RuntimeException(e);
         }
@@ -146,9 +174,15 @@ public class IrisPackBenchmarking {
         IrisToolbelt.pregenerate(PregenTask
                 .builder()
                 .gui(gui)
-                .width(radius)
+                .radiusX(diameter)
-                .height(radius)
+                .radiusZ(diameter)
-                .build(), Bukkit.getWorld("benchmark")
+                .build(), headless ?
+                new HeadlessPregenMethod(engine) :
+                new HybridPregenMethod(
+                        engine.getWorld().realWorld(),
+                        IrisSettings.getThreadCount(IrisSettings.get().getConcurrency().getParallelism())
+                ),
+                engine
         );
     }
 
@@ -178,26 +212,4 @@ public class IrisPackBenchmarking {
     private int findHighest(KList<Integer> list) {
         return Collections.max(list);
     }
-
-    private boolean deleteDirectory(Path dir) {
-        try {
-            Files.walkFileTree(dir, new SimpleFileVisitor<>() {
-                @Override
-                public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
-                    Files.delete(file);
-                    return FileVisitResult.CONTINUE;
-                }
-
-                @Override
-                public FileVisitResult postVisitDirectory(Path dir, IOException exc) throws IOException {
-                    Files.delete(dir);
-                    return FileVisitResult.CONTINUE;
-                }
-            });
-            return true;
-        } catch (IOException e) {
-            e.printStackTrace();
-            return false;
-        }
-    }
 }

core/src/main/java/com/volmit/iris/engine/IrisEngine.java

@@ -304,6 +304,11 @@ public class IrisEngine implements Engine {
         return generated.get();
     }
 
+    @Override
+    public void addGenerated(int x, int z) {
+        generated.incrementAndGet();
+    }
+
     @Override
     public double getGeneratedPerSecond() {
         if (perSecondLatch.flip()) {

core/src/main/java/com/volmit/iris/engine/framework/Engine.java

@@ -610,6 +610,9 @@ public interface Engine extends DataProvider, Fallible, LootProvider, BlockUpdat
 
     int getGenerated();
 
+    @ChunkCoordinates
+    void addGenerated(int x, int z);
+
     CompletableFuture<Long> getHash32();
 
     default <T> IrisPosition lookForStreamResult(T find, ProceduralStream<T> stream, Function2<T, T, Boolean> matcher, long timeout) {

core/src/main/java/com/volmit/iris/engine/object/IrisContextInjector.java

@@ -3,6 +3,7 @@ package com.volmit.iris.engine.object;
 import com.volmit.iris.core.nms.INMS;
 import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.util.misc.ServerProperties;
+import lombok.Getter;
 import org.bukkit.Bukkit;
 import org.bukkit.configuration.ConfigurationSection;
 import org.bukkit.configuration.file.YamlConfiguration;
@@ -15,6 +16,8 @@ import java.util.List;
 import static com.volmit.iris.Iris.instance;
 
 public class IrisContextInjector implements Listener {
+    @Getter
+    private static boolean missingDimensionTypes = false;
     private AutoClosing autoClosing = null;
     private final int totalWorlds;
     private int worldCounter = 0;
@@ -35,6 +38,12 @@ public class IrisContextInjector implements Listener {
         if (Bukkit.getAllowNether()) i++;
         if (Bukkit.getAllowEnd()) i++;
 
+        if (INMS.get().missingDimensionTypes(overworld, nether, end)) {
+            missingDimensionTypes = true;
+            totalWorlds = 0;
+            return;
+        }
+
         if (overworld || nether || end) {
             var pair = INMS.get().injectUncached(overworld, nether, end);
             i += pair.getA() - 3;
@@ -42,6 +51,7 @@ public class IrisContextInjector implements Listener {
         }
 
         totalWorlds = i;
+        instance.registerListener(this);
     }
 
     @EventHandler

core/src/main/java/com/volmit/iris/engine/object/IrisHeadless.java

@@ -0,0 +1,325 @@
+/*
+ *  Iris is a World Generator for Minecraft Bukkit Servers
+ *  Copyright (c) 2024 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.volmit.iris.engine.object;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.INMS;
+import com.volmit.iris.core.nms.headless.IRegion;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.core.pregenerator.PregenListener;
+import com.volmit.iris.engine.data.cache.Cache;
+import com.volmit.iris.engine.framework.Engine;
+import com.volmit.iris.engine.framework.EngineStage;
+import com.volmit.iris.engine.framework.WrongEngineBroException;
+import com.volmit.iris.util.collection.KMap;
+import com.volmit.iris.util.context.ChunkContext;
+import com.volmit.iris.util.context.IrisContext;
+import com.volmit.iris.util.documentation.BlockCoordinates;
+import com.volmit.iris.util.documentation.RegionCoordinates;
+import com.volmit.iris.util.hunk.Hunk;
+import com.volmit.iris.util.hunk.view.BiomeGridHunkHolder;
+import com.volmit.iris.util.hunk.view.SyncChunkDataHunkHolder;
+import com.volmit.iris.util.mantle.MantleFlag;
+import com.volmit.iris.util.math.M;
+import com.volmit.iris.util.math.Position2;
+import com.volmit.iris.util.parallel.MultiBurst;
+import com.volmit.iris.util.scheduling.J;
+import com.volmit.iris.util.scheduling.Looper;
+import com.volmit.iris.util.scheduling.PrecisionStopwatch;
+import org.bukkit.Material;
+import org.bukkit.block.data.BlockData;
+
+import java.io.IOException;
+import java.util.concurrent.*;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.concurrent.atomic.AtomicReferenceArray;
+import java.util.function.Consumer;
+
+public class IrisHeadless {
+    private final long KEEP_ALIVE = TimeUnit.SECONDS.toMillis(10L);
+    private final Engine engine;
+    private final IRegionStorage storage;
+    private final ExecutorService executor = Executors.newCachedThreadPool();
+    private final KMap<Long, Region> regions = new KMap<>();
+    private final AtomicInteger loadedChunks = new AtomicInteger();
+    private transient CompletingThread regionThread;
+    private transient boolean closed = false;
+
+    public IrisHeadless(Engine engine) {
+        this.engine = engine;
+        this.storage = INMS.get().createRegionStorage(engine);
+        if (storage == null) throw new IllegalStateException("Failed to create region storage!");
+        engine.getWorld().headless(this);
+        startRegionCleaner();
+    }
+
+    private void startRegionCleaner() {
+        var cleaner = new Looper() {
+            @Override
+            protected long loop() {
+                if (closed) return -1;
+                long time = M.ms() - KEEP_ALIVE;
+                regions.values()
+                        .stream()
+                        .filter(r -> r.lastEntry < time)
+                        .forEach(Region::submit);
+                return closed ? -1 : 1000;
+            }
+        };
+        cleaner.setName("Iris Region Cleaner - " + engine.getWorld().name());
+        cleaner.setPriority(Thread.MIN_PRIORITY);
+        cleaner.start();
+    }
+
+    public int getLoadedChunks() {
+        return loadedChunks.get();
+    }
+
+    /**
+     * Checks if the mca plate is fully generated or not.
+     *
+     * @param x coord of the chunk
+     * @param z coord of the chunk
+     * @return true if the chunk exists in .mca
+     */
+    public boolean exists(int x, int z) {
+        if (closed) return false;
+        if (engine.getWorld().hasRealWorld() && engine.getWorld().realWorld().isChunkLoaded(x, z))
+            return true;
+        return storage.exists(x, z);
+    }
+
+    public synchronized CompletableFuture<Void> generateRegion(MultiBurst burst, int x, int z, int maxConcurrent, PregenListener listener) {
+        if (closed) return CompletableFuture.completedFuture(null);
+        if (regionThread != null && !regionThread.future.isDone())
+            throw new IllegalStateException("Region generation already in progress");
+
+        regionThread = new CompletingThread(() -> {
+            boolean listening = listener != null;
+            Semaphore semaphore = new Semaphore(maxConcurrent);
+            CountDownLatch latch = new CountDownLatch(1024);
+
+            iterateRegion(x, z, pos -> {
+                try {
+                    semaphore.acquire();
+                } catch (InterruptedException e) {
+                    semaphore.release();
+                    return;
+                }
+
+                burst.complete(() -> {
+                    try {
+                        if (listening) listener.onChunkGenerating(pos.getX(), pos.getZ());
+                        generateChunk(pos.getX(), pos.getZ());
+                        if (listening) listener.onChunkGenerated(pos.getX(), pos.getZ());
+                    } finally {
+                        semaphore.release();
+                        latch.countDown();
+                    }
+                });
+            });
+            try {
+                latch.await();
+            } catch (InterruptedException ignored) {}
+            if (listening) listener.onRegionGenerated(x, z);
+        }, "Region Generator - " + x + "," + z, Thread.MAX_PRIORITY);
+
+        return regionThread.future;
+    }
+
+    @RegionCoordinates
+    private static void iterateRegion(int x, int z, Consumer<Position2> chunkPos) {
+        int cX = x << 5;
+        int cZ = z << 5;
+        for (int xx = 0; xx < 32; xx++) {
+            for (int zz = 0; zz < 32; zz++) {
+                chunkPos.accept(new Position2(cX + xx, cZ + zz));
+            }
+        }
+    }
+
+    public void generateChunk(int x, int z) {
+        if (closed || exists(x, z)) return;
+        try {
+            var chunk = storage.createChunk(x, z);
+            loadedChunks.incrementAndGet();
+
+            SyncChunkDataHunkHolder blocks = new SyncChunkDataHunkHolder(chunk);
+            BiomeGridHunkHolder biomes = new BiomeGridHunkHolder(chunk, chunk.getMinHeight(), chunk.getMaxHeight());
+            ChunkContext ctx = generate(engine, x << 4, z << 4, blocks, biomes);
+            blocks.apply();
+            biomes.apply();
+
+            storage.fillBiomes(chunk, ctx);
+            chunk.mark();
+
+            long key = Cache.key(x >> 5, z >> 5);
+            regions.computeIfAbsent(key, Region::new)
+                    .add(chunk);
+        } catch (Throwable e) {
+            loadedChunks.decrementAndGet();
+            Iris.error("Failed to generate " + x + ", " + z);
+            e.printStackTrace();
+        }
+    }
+
+    @BlockCoordinates
+    private ChunkContext generate(Engine engine, int x, int z, Hunk<BlockData> vblocks, Hunk<org.bukkit.block.Biome> vbiomes) throws WrongEngineBroException {
+        if (engine.isClosed()) {
+            throw new WrongEngineBroException();
+        }
+
+        engine.getContext().touch();
+        engine.getEngineData().getStatistics().generatedChunk();
+        ChunkContext ctx = null;
+        try {
+            PrecisionStopwatch p = PrecisionStopwatch.start();
+            Hunk<BlockData> blocks = vblocks.listen((xx, y, zz, t) -> engine.catchBlockUpdates(x + xx, y + engine.getMinHeight(), z + zz, t));
+
+            var dimension = engine.getDimension();
+            if (dimension.isDebugChunkCrossSections() && ((x >> 4) % dimension.getDebugCrossSectionsMod() == 0 || (z >> 4) % dimension.getDebugCrossSectionsMod() == 0)) {
+                for (int i = 0; i < 16; i++) {
+                    for (int j = 0; j < 16; j++) {
+                        blocks.set(i, 0, j, Material.CRYING_OBSIDIAN.createBlockData());
+                    }
+                }
+            } else {
+                ctx = new ChunkContext(x, z, engine.getComplex());
+                IrisContext.getOr(engine).setChunkContext(ctx);
+
+                for (EngineStage i : engine.getMode().getStages()) {
+                    i.generate(x, z, blocks, vbiomes, false, ctx);
+                }
+            }
+
+            engine.getMantle().getMantle().flag(x >> 4, z >> 4, MantleFlag.REAL, true);
+            engine.getMetrics().getTotal().put(p.getMilliseconds());
+            engine.addGenerated(x,z);
+        } catch (Throwable e) {
+            Iris.reportError(e);
+            engine.fail("Failed to generate " + x + ", " + z, e);
+        }
+        return ctx;
+    }
+
+    public void close() throws IOException {
+        if (closed) return;
+        try {
+            if (regionThread != null) {
+                regionThread.future.join();
+                regionThread = null;
+            }
+
+            regions.v().forEach(Region::submit);
+            Iris.info("Waiting for " + loadedChunks.get() + " chunks to unload...");
+            while (loadedChunks.get() > 0)
+                J.sleep(1);
+            Iris.info("All chunks unloaded");
+            executor.shutdown();
+            storage.close();
+            engine.getWorld().headless(null);
+        } finally {
+            closed = true;
+        }
+    }
+
+    private class Region implements Runnable {
+        private final int x, z;
+        private final long key;
+        private final AtomicReferenceArray<SerializableChunk> chunks = new AtomicReferenceArray<>(1024);
+        private final AtomicReference<Future<?>> full = new AtomicReference<>();
+        private transient int size;
+        private transient long lastEntry = M.ms();
+
+        public Region(long key) {
+            this.x = Cache.keyX(key);
+            this.z = Cache.keyZ(key);
+            this.key = key;
+        }
+
+        @Override
+        public void run() {
+            try (IRegion region = storage.getRegion(x, z, false)) {
+                assert region != null;
+
+                for (int i = 0; i < 1024; i++) {
+                    SerializableChunk chunk = chunks.get(i);
+                    if (chunk == null)
+                        continue;
+
+                    try {
+                        region.write(chunk);
+                    } catch (Throwable e) {
+                        Iris.error("Failed to save chunk " + chunk.getPos());
+                        e.printStackTrace();
+                    }
+                    loadedChunks.decrementAndGet();
+                }
+            } catch (Throwable e) {
+                Iris.error("Failed to load region file " + x + ", " + z);
+                e.printStackTrace();
+                loadedChunks.addAndGet(-size);
+            }
+        }
+
+        public synchronized void add(SerializableChunk chunk) {
+            lastEntry = M.ms();
+            if (chunks.getAndSet(index(chunk.getPos()), chunk) != null)
+                throw new IllegalStateException("Chunk " + chunk.getPos() + " already exists");
+            if (++size < 1024)
+                return;
+            submit();
+        }
+
+        public void submit() {
+            regions.remove(key);
+            full.getAndUpdate(future -> {
+                if (future != null) return future;
+                return executor.submit(this);
+            });
+        }
+
+        private int index(Position2 chunk) {
+            int x = chunk.getX() & 31;
+            int z = chunk.getZ() & 31;
+            return z * 32 + x;
+        }
+    }
+
+    private static class CompletingThread extends Thread {
+        private final CompletableFuture<Void> future = new CompletableFuture<>();
+
+        private CompletingThread(Runnable task, String name, int priority) {
+            super(task, name);
+            setPriority(priority);
+            start();
+        }
+
+        @Override
+        public void run() {
+            try {
+                super.run();
+            } finally {
+                future.complete(null);
+            }
+        }
+    }
+}

core/src/main/java/com/volmit/iris/engine/object/IrisWorld.java

@@ -48,6 +48,7 @@ public class IrisWorld {
     private long seed;
     private World.Environment environment;
     private World realWorld;
+    private IrisHeadless headless;
     private int minHeight;
     private int maxHeight;
 

core/src/main/java/com/volmit/iris/engine/platform/BukkitChunkGenerator.java

@@ -21,6 +21,8 @@ package com.volmit.iris.engine.platform;
 import com.volmit.iris.Iris;
 import com.volmit.iris.core.loader.IrisData;
 import com.volmit.iris.core.nms.INMS;
+import com.volmit.iris.core.pregenerator.EmptyListener;
+import com.volmit.iris.core.pregenerator.methods.HeadlessPregenMethod;
 import com.volmit.iris.core.service.StudioSVC;
 import com.volmit.iris.engine.IrisEngine;
 import com.volmit.iris.engine.data.chunk.TerrainChunk;
@@ -32,10 +34,13 @@ import com.volmit.iris.engine.object.StudioMode;
 import com.volmit.iris.engine.platform.studio.StudioGenerator;
 import com.volmit.iris.util.collection.KList;
 import com.volmit.iris.util.data.IrisBiomeStorage;
+import com.volmit.iris.util.format.C;
+import com.volmit.iris.util.format.Form;
 import com.volmit.iris.util.hunk.Hunk;
 import com.volmit.iris.util.hunk.view.BiomeGridHunkHolder;
 import com.volmit.iris.util.hunk.view.ChunkDataHunkHolder;
 import com.volmit.iris.util.io.ReactiveFolder;
+import com.volmit.iris.util.plugin.VolmitSender;
 import com.volmit.iris.util.scheduling.ChronoLatch;
 import com.volmit.iris.util.scheduling.J;
 import com.volmit.iris.util.scheduling.Looper;
@@ -252,6 +257,10 @@ public class BukkitChunkGenerator extends ChunkGenerator implements PlatformChun
     }
 
     private Engine getEngine(WorldInfo world) {
+        return getEngine(world.getSeed());
+    }
+
+    private Engine getEngine(long seed) {
         if (setup.get()) {
             return getEngine();
         }
@@ -264,7 +273,7 @@ public class BukkitChunkGenerator extends ChunkGenerator implements PlatformChun
             }
 
 
-            getWorld().setRawWorldSeed(world.getSeed());
+            getWorld().setRawWorldSeed(seed);
             setupEngine();
             setup.set(true);
             this.hotloader = studio ? new Looper() {
@@ -335,6 +344,21 @@ public class BukkitChunkGenerator extends ChunkGenerator implements PlatformChun
         getEngine(world);
     }
 
+    @Override
+    public void prepareSpawnChunks(long seed, int radius) {
+        if (radius < 0 || new File(world.worldFolder(), "level.dat").exists())
+            return;
+        var engine = getEngine(seed);
+        var headless = new HeadlessPregenMethod(engine, 4);
+
+        for (int x = -radius; x <= radius; x++) {
+            for (int z = -radius; z <= radius; z++) {
+                headless.generateChunk(x, z, EmptyListener.INSTANCE);
+            }
+        }
+        headless.close();
+    }
+
     @Override
     public void generateNoise(@NotNull WorldInfo world, @NotNull Random random, int x, int z, @NotNull ChunkGenerator.ChunkData d) {
         try {

core/src/main/java/com/volmit/iris/engine/platform/PlatformChunkGenerator.java

@@ -49,4 +49,12 @@ public interface PlatformChunkGenerator extends Hotloadable, DataProvider {
     void touch(World world);
 
     CompletableFuture<Integer> getSpawnChunks();
+
+    void prepareSpawnChunks(long seed, int radius);
+
+    default int getGenerated() {
+        Engine engine = getEngine();
+        if (engine == null) return 0;
+        return engine.getGenerated();
+    }
 }

core/src/main/java/com/volmit/iris/util/hunk/view/SyncChunkDataHunkHolder.java

@@ -0,0 +1,48 @@
+package com.volmit.iris.util.hunk.view;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.util.hunk.storage.ArrayHunk;
+import org.bukkit.Material;
+import org.bukkit.block.data.BlockData;
+import org.bukkit.generator.ChunkGenerator;
+
+public class SyncChunkDataHunkHolder extends ArrayHunk<BlockData> {
+    private static final BlockData AIR = Material.AIR.createBlockData();
+    private final ChunkGenerator.ChunkData chunk;
+    private final Thread mainThread = Thread.currentThread();
+
+    public SyncChunkDataHunkHolder(ChunkGenerator.ChunkData chunk) {
+        super(16, chunk.getMaxHeight() - chunk.getMinHeight(), 16);
+        this.chunk = chunk;
+    }
+
+    @Override
+    public void setRaw(int x, int y, int z, BlockData data) {
+        if (Thread.currentThread() != mainThread)
+            Iris.warn("SyncChunkDataHunkHolder is not on the main thread");
+        super.setRaw(x, y, z, data);
+    }
+
+    @Override
+    public BlockData getRaw(int x, int y, int z) {
+        if (Thread.currentThread() != mainThread)
+            Iris.warn("SyncChunkDataHunkHolder is not on the main thread");
+        BlockData b = super.getRaw(x, y, z);
+
+        return b != null ? b : AIR;
+    }
+
+    public void apply() {
+        for (int i = getHeight()-1; i >= 0; i--) {
+            for (int j = 0; j < getWidth(); j++) {
+                for (int k = 0; k < getDepth(); k++) {
+                    BlockData b = super.getRaw(j, i, k);
+
+                    if (b != null) {
+                        chunk.setBlock(j, i + chunk.getMinHeight(), k, b);
+                    }
+                }
+            }
+        }
+    }
+}

core/src/main/java/com/volmit/iris/util/math/Position2.java

@@ -21,6 +21,8 @@ package com.volmit.iris.util.math;
 import com.volmit.iris.engine.object.IrisPosition;
 import org.bukkit.util.Vector;
 
+import java.util.function.BiFunction;
+
 public class Position2 {
     private int x;
     private int z;
@@ -94,4 +96,8 @@ public class Position2 {
     public IrisPosition toIris() {
         return new IrisPosition(x, 23, z);
     }
+
+    public <T> T convert(BiFunction<Integer, Integer, T> constructor) {
+        return constructor.apply(x, z);
+    }
 }

core/src/main/java/com/volmit/iris/util/math/Spiraler.java

@@ -63,7 +63,7 @@ public class Spiraler {
 
     public void next() {
         if ((-sizeX / 2 <= x) && (x <= sizeX / 2) && (-sizeZ / 2 <= z) && (z <= sizeZ / 2)) {
-            spiraled.on(x + ox, z + ox);
+            spiraled.on(x + ox, z + oz);
         }
 
         if ((x == z) || ((x < 0) && (x == -z)) || ((x > 0) && (x == 1 - z))) {

core/src/main/java/com/volmit/iris/util/misc/ServerProperties.java

@@ -10,7 +10,7 @@ public class ServerProperties {
     public static final File SERVER_PROPERTIES;
     public static final File BUKKIT_YML;
 
-    public static final String LEVEL_NAME = DATA.getProperty("level-name", "world");
+    public static final String LEVEL_NAME;
 
     static {
         String[] args = ProcessHandle.current()
@@ -20,11 +20,13 @@ public class ServerProperties {
 
         String propertiesPath = "server.properties";
         String bukkitYml = "bukkit.yml";
+        String levelName = null;
 
         for (int i = 0; i < args.length - 1; i++) {
             switch (args[i]) {
                 case "-c", "--config" -> propertiesPath = args[i + 1];
                 case "-b", "--bukkit-settings" -> bukkitYml = args[i + 1];
+                case "-w", "--level-name", "--world" -> levelName = args[i + 1];
             }
         }
 
@@ -35,5 +37,8 @@ public class ServerProperties {
         } catch (IOException e) {
             throw new RuntimeException(e);
         }
+
+        if (levelName != null) LEVEL_NAME = levelName;
+        else LEVEL_NAME = DATA.getProperty("level-name", "world");
     }
 }

nms/v1_20_R1/src/main/java/com/volmit/iris/core/nms/v1_20_R1/NMSBinding.java

@@ -7,6 +7,8 @@ import com.volmit.iris.Iris;
 import com.volmit.iris.core.nms.INMSBinding;
 import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
+import com.volmit.iris.core.nms.v1_20_R1.headless.RegionStorage;
 import com.volmit.iris.engine.data.cache.AtomicCache;
 import com.volmit.iris.engine.framework.Engine;
 import com.volmit.iris.util.collection.KList;
@@ -38,7 +40,9 @@ import net.minecraft.tags.TagKey;
 import net.minecraft.world.entity.EntityDimensions;
 import net.minecraft.world.level.LevelReader;
 import net.minecraft.world.level.biome.BiomeSource;
+import net.minecraft.world.level.biome.Biomes;
 import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.EntityBlock;
 import net.minecraft.world.level.block.entity.BlockEntity;
 import net.minecraft.world.level.block.state.BlockState;
@@ -47,6 +51,9 @@ import net.minecraft.world.level.chunk.ChunkStatus;
 import net.minecraft.world.level.chunk.LevelChunk;
 import net.minecraft.world.level.dimension.DimensionType;
 import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.FlatLevelSource;
+import net.minecraft.world.level.levelgen.flat.FlatLayerInfo;
+import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
 import org.bukkit.*;
 import org.bukkit.block.Biome;
 import org.bukkit.block.data.BlockData;
@@ -639,6 +646,11 @@ public class NMSBinding implements INMSBinding {
         }
     }
 
+    @Override
+    public IRegionStorage createRegionStorage(Engine engine) {
+        return new RegionStorage(engine);
+    }
+
     @Override
     public AutoClosing injectLevelStems() {
         return inject(this::supplier);
@@ -673,6 +685,15 @@ public class NMSBinding implements INMSBinding {
                 }));
     }
 
+    @Override
+    public boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end) {
+        var registry = registry().registryOrThrow(Registries.DIMENSION_TYPE);
+        if (overworld) overworld = !registry.containsKey(createIrisKey(LevelStem.OVERWORLD));
+        if (nether) nether = !registry.containsKey(createIrisKey(LevelStem.NETHER));
+        if (end) end = !registry.containsKey(createIrisKey(LevelStem.END));
+        return overworld || nether || end;
+    }
+
     private WorldLoader.DataLoadContext supplier(WorldLoader.DataLoadContext old) {
         return dataLoadContext.aquire(() -> new WorldLoader.DataLoadContext(
                 old.resources(),
@@ -703,23 +724,32 @@ public class NMSBinding implements INMSBinding {
     private RegistryAccess.Frozen createRegistryAccess(RegistryAccess.Frozen datapack, boolean copy, boolean overworld, boolean nether, boolean end) {
         var access = registry();
         var dimensions = access.registryOrThrow(Registries.DIMENSION_TYPE);
-        var levelStems = access.registryOrThrow(Registries.LEVEL_STEM);
 
+        var settings = new FlatLevelGeneratorSettings(
+                Optional.empty(),
+                access.lookupOrThrow(Registries.BIOME).getOrThrow(Biomes.THE_VOID),
+                List.of()
+        );
+        settings.getLayersInfo().add(new FlatLayerInfo(1, Blocks.AIR));
+        settings.updateLayers();
+
+        var source = new FlatLevelSource(settings);
         var fake = new MappedRegistry<>(Registries.LEVEL_STEM, Lifecycle.experimental());
-        if (overworld) register(fake, levelStems, dimensions, LevelStem.OVERWORLD);
+        if (overworld) register(fake, dimensions, source, LevelStem.OVERWORLD);
-        if (nether) register(fake, levelStems, dimensions, LevelStem.NETHER);
+        if (nether) register(fake, dimensions, source, LevelStem.NETHER);
-        if (end) register(fake, levelStems, dimensions, LevelStem.END);
+        if (end) register(fake, dimensions, source, LevelStem.END);
         copy(fake, datapack.registry(Registries.LEVEL_STEM).orElse(null));
 
-        if (copy) copy(fake, levelStems);
+        if (copy) copy(fake, access.registryOrThrow(Registries.LEVEL_STEM));
 
         return new RegistryAccess.Frozen.ImmutableRegistryAccess(List.of(fake.freeze())).freeze();
     }
 
-    private void register(MappedRegistry<LevelStem> target, Registry<LevelStem> levelStems, Registry<DimensionType> dimensions, ResourceKey<LevelStem> key) {
+    private void register(MappedRegistry<LevelStem> target, Registry<DimensionType> dimensions, FlatLevelSource source, ResourceKey<LevelStem> key) {
+        var loc = createIrisKey(key);
         target.register(key, new LevelStem(
-                dimensions.getHolderOrThrow(ResourceKey.create(Registries.DIMENSION_TYPE, new ResourceLocation("iris", key.location().getPath()))),
+                dimensions.getHolder(ResourceKey.create(Registries.DIMENSION_TYPE, loc)).orElseThrow(() -> new IllegalStateException("Missing dimension type " + loc + " in " + dimensions.keySet())),
-                levelStems.getOrThrow(key).generator()
+                source
         ), Lifecycle.stable());
     }
 
@@ -732,4 +762,8 @@ public class NMSBinding implements INMSBinding {
                 target.register(key, value, info);
         });
     }
+
+    private ResourceLocation createIrisKey(ResourceKey<LevelStem> key) {
+        return new ResourceLocation("iris", key.location().getPath());
+    }
 }

nms/v1_20_R1/src/main/java/com/volmit/iris/core/nms/v1_20_R1/headless/DirectTerrainChunk.java

@@ -0,0 +1,215 @@
+package com.volmit.iris.core.nms.v1_20_R1.headless;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.BiomeBaseInjector;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.util.data.IrisCustomData;
+import com.volmit.iris.util.math.Position2;
+import lombok.Data;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Registry;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.EntityBlock;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkStatus;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import org.bukkit.Material;
+import org.bukkit.block.Biome;
+import org.bukkit.block.data.BlockData;
+import org.bukkit.craftbukkit.v1_20_R1.block.CraftBlock;
+import org.bukkit.craftbukkit.v1_20_R1.block.data.CraftBlockData;
+import org.bukkit.craftbukkit.v1_20_R1.util.CraftMagicNumbers;
+import org.bukkit.generator.ChunkGenerator;
+import org.bukkit.material.MaterialData;
+import org.jetbrains.annotations.NotNull;
+
+import static com.volmit.iris.core.nms.v1_20_R1.headless.RegionStorage.registryAccess;
+
+@Data
+public final class DirectTerrainChunk implements SerializableChunk {
+    private final ProtoChunk access;
+    private final int minHeight, maxHeight;
+    private final Registry<net.minecraft.world.level.biome.Biome> biomes;
+
+    public DirectTerrainChunk(ProtoChunk access) {
+        this.access = access;
+        this.minHeight = access.getMinBuildHeight();
+        this.maxHeight = access.getMaxBuildHeight();
+        this.biomes = registryAccess().registryOrThrow(net.minecraft.core.registries.Registries.BIOME);
+    }
+
+    @Override
+    public BiomeBaseInjector getBiomeBaseInjector() {
+        return null;
+    }
+
+    @NotNull
+    @Override
+    public Biome getBiome(int x, int z) {
+        return getBiome(x, 0, z);
+    }
+
+    @NotNull
+    @Override
+    public Biome getBiome(int x, int y, int z) {
+        if (y < minHeight || y > maxHeight) return Biome.PLAINS;
+        return CraftBlock.biomeBaseToBiome(biomes, access.getNoiseBiome(x >> 2, y >> 2, z >> 2));
+    }
+
+    @Override
+    public void setBiome(int x, int z, Biome bio) {
+        for (int y = minHeight; y < maxHeight; y += 4) {
+            setBiome(x, y, z, bio);
+        }
+    }
+
+    @Override
+    public void setBiome(int x, int y, int z, Biome bio) {
+        if (y < minHeight || y > maxHeight) return;
+        access.setBiome(x & 15, y, z & 15, CraftBlock.biomeToBiomeBase(biomes, bio));
+    }
+
+    public void setBlock(int x, int y, int z, Material material) {
+        this.setBlock(x, y, z, material.createBlockData());
+    }
+
+    public void setBlock(int x, int y, int z, MaterialData material) {
+        this.setBlock(x, y, z, CraftMagicNumbers.getBlock(material));
+    }
+
+    @Override
+    public void setBlock(int x, int y, int z, BlockData blockData) {
+        if (blockData == null) {
+            Iris.error("NULL BD");
+        }
+        if (blockData instanceof IrisCustomData data)
+            blockData = data.getBase();
+        if (!(blockData instanceof CraftBlockData craftBlockData))
+            throw new IllegalArgumentException("Expected CraftBlockData, got " + blockData.getClass().getSimpleName() + " instead");
+        access.setBlockState(new BlockPos(x & 15, y, z & 15), craftBlockData.getState(), false);
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, Material material) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, material.createBlockData());
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, MaterialData material) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, CraftMagicNumbers.getBlock(material));
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, BlockData blockData) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, ((CraftBlockData) blockData).getState());
+    }
+
+    public Material getType(int x, int y, int z) {
+        return CraftMagicNumbers.getMaterial(this.getTypeId(x, y, z).getBlock());
+    }
+
+    public MaterialData getTypeAndData(int x, int y, int z) {
+        return CraftMagicNumbers.getMaterial(this.getTypeId(x, y, z));
+    }
+
+    public BlockData getBlockData(int x, int y, int z) {
+        return CraftBlockData.fromData(this.getTypeId(x, y, z));
+    }
+
+    @Override
+    public ChunkGenerator.ChunkData getRaw() {
+        return null;
+    }
+
+    @Override
+    public void setRaw(ChunkGenerator.ChunkData data) {
+
+    }
+
+    @Override
+    public void inject(ChunkGenerator.BiomeGrid biome) {
+
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, BlockState type) {
+        if (xMin > 15 || yMin >= this.maxHeight || zMin > 15)
+            return;
+
+        if (xMin < 0) {
+            xMin = 0;
+        }
+
+        if (yMin < this.minHeight) {
+            yMin = this.minHeight;
+        }
+
+        if (zMin < 0) {
+            zMin = 0;
+        }
+
+        if (xMax > 16) {
+            xMax = 16;
+        }
+
+        if (yMax > this.maxHeight) {
+            yMax = this.maxHeight;
+        }
+
+        if (zMax > 16) {
+            zMax = 16;
+        }
+
+        if (xMin >= xMax || yMin >= yMax || zMin >= zMax)
+            return;
+
+        for (int y = yMin; y < yMax; ++y) {
+            for (int x = xMin; x < xMax; ++x) {
+                for (int z = zMin; z < zMax; ++z) {
+                    this.setBlock(x, y, z, type);
+                }
+            }
+        }
+
+    }
+
+    public BlockState getTypeId(int x, int y, int z) {
+        if (x != (x & 15) || y < this.minHeight || y >= this.maxHeight || z != (z & 15))
+            return Blocks.AIR.defaultBlockState();
+        return access.getBlockState(new BlockPos(access.getPos().getMinBlockX() + x, y, access.getPos().getMinBlockZ() + z));
+    }
+
+    public byte getData(int x, int y, int z) {
+        return CraftMagicNumbers.toLegacyData(this.getTypeId(x, y, z));
+    }
+
+    private void setBlock(int x, int y, int z, BlockState type) {
+        if (x != (x & 15) || y < this.minHeight || y >= this.maxHeight || z != (z & 15))
+            return;
+        BlockPos blockPosition = new BlockPos(access.getPos().getMinBlockX() + x, y, access.getPos().getMinBlockZ() + z);
+        BlockState oldBlockData = access.setBlockState(blockPosition, type, false);
+        if (type.hasBlockEntity()) {
+            BlockEntity tileEntity = ((EntityBlock) type.getBlock()).newBlockEntity(blockPosition, type);
+            if (tileEntity == null) {
+                access.removeBlockEntity(blockPosition);
+            } else {
+                access.setBlockEntity(tileEntity);
+            }
+        } else if (oldBlockData != null && oldBlockData.hasBlockEntity()) {
+            access.removeBlockEntity(blockPosition);
+        }
+
+    }
+
+    @Override
+    public Position2 getPos() {
+        return new Position2(access.getPos().x, access.getPos().z);
+    }
+
+    @Override
+    public Object serialize() {
+        return RegionStorage.serialize(access);
+    }
+
+    @Override
+    public void mark() {
+        access.setStatus(ChunkStatus.FULL);
+    }
+}

nms/v1_20_R1/src/main/java/com/volmit/iris/core/nms/v1_20_R1/headless/Region.java

@@ -0,0 +1,72 @@
+package com.volmit.iris.core.nms.v1_20_R1.headless;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.headless.IRegion;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.util.math.M;
+import lombok.NonNull;
+import lombok.Synchronized;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.NbtIo;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.chunk.storage.RegionFile;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.nio.file.Path;
+
+class Region implements IRegion, Comparable<Region> {
+    private final RegionFile regionFile;
+    transient long references;
+    transient long lastUsed;
+
+    Region(Path path, Path folder) throws IOException {
+        this.regionFile = new RegionFile(path, folder, false);
+    }
+
+    @Override
+    @Synchronized
+    public boolean exists(int x, int z) {
+        try (DataInputStream din = regionFile.getChunkDataInputStream(new ChunkPos(x, z))) {
+            if (din == null) return false;
+            return !"empty".equals(NbtIo.read(din).getString("Status"));
+        } catch (IOException e) {
+            return false;
+        }
+    }
+
+    @Override
+    @Synchronized
+    public void write(@NonNull SerializableChunk chunk) throws IOException {
+        try (DataOutputStream dos = regionFile.getChunkDataOutputStream(chunk.getPos().convert(ChunkPos::new))) {
+            NbtIo.write((CompoundTag) chunk.serialize(), dos);
+        }
+    }
+
+    @Override
+    public void close() {
+        --references;
+        lastUsed = M.ms();
+    }
+
+    public boolean unused() {
+        return references <= 0;
+    }
+
+    public boolean remove() {
+        if (!unused()) return false;
+        try {
+            regionFile.close();
+        } catch (IOException e) {
+            Iris.error("Failed to close region file");
+            e.printStackTrace();
+        }
+        return true;
+    }
+
+    @Override
+    public int compareTo(Region o) {
+        return Long.compare(lastUsed, o.lastUsed);
+    }
+}

nms/v1_20_R1/src/main/java/com/volmit/iris/core/nms/v1_20_R1/headless/RegionStorage.java

@@ -0,0 +1,312 @@
+package com.volmit.iris.core.nms.v1_20_R1.headless;
+
+import com.mojang.logging.LogUtils;
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.DataResult;
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.headless.IRegion;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.engine.data.cache.AtomicCache;
+import com.volmit.iris.engine.data.cache.Cache;
+import com.volmit.iris.engine.framework.Engine;
+import com.volmit.iris.engine.object.IrisBiome;
+import com.volmit.iris.util.collection.KMap;
+import com.volmit.iris.util.context.ChunkContext;
+import com.volmit.iris.util.math.RNG;
+import com.volmit.iris.util.scheduling.J;
+import lombok.Getter;
+import lombok.NonNull;
+import net.minecraft.FileUtil;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.Registry;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.nbt.*;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.chunk.*;
+import net.minecraft.world.level.levelgen.BelowZeroRetrogen;
+import net.minecraft.world.level.levelgen.GenerationStep;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.blending.BlendingData;
+import org.bukkit.Bukkit;
+import org.bukkit.craftbukkit.v1_20_R1.CraftServer;
+import org.bukkit.craftbukkit.v1_20_R1.block.CraftBlock;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Map;
+import java.util.Optional;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+import static net.minecraft.world.level.chunk.storage.ChunkSerializer.BLOCK_STATE_CODEC;
+import static net.minecraft.world.level.chunk.storage.ChunkSerializer.packOffsets;
+
+public class RegionStorage implements IRegionStorage, LevelHeightAccessor {
+    private static final AtomicCache<RegistryAccess> CACHE = new AtomicCache<>();
+    private final KMap<Long, Region> regions = new KMap<>();
+    private final Path folder;
+
+    private final Engine engine;
+    private final KMap<String, Holder<Biome>> customBiomes = new KMap<>();
+    private final KMap<org.bukkit.block.Biome, Holder<Biome>> minecraftBiomes;
+    private final RNG biomeRng;
+    private final @Getter int minBuildHeight;
+    private final @Getter int height;
+
+    private transient boolean closed = false;
+
+    public RegionStorage(Engine engine) {
+        this.engine = engine;
+        this.folder = new File(engine.getWorld().worldFolder(), "region").toPath();
+        this.biomeRng = new RNG(engine.getSeedManager().getBiome());
+
+        this.minBuildHeight = engine.getDimension().getMinHeight();
+        this.height = engine.getDimension().getMaxHeight() - minBuildHeight;
+
+        AtomicInteger failed = new AtomicInteger();
+        var dimKey = engine.getDimension().getLoadKey();
+        for (var biome : engine.getAllBiomes()) {
+            if (!biome.isCustom()) continue;
+            for (var custom : biome.getCustomDerivitives()) {
+                biomeHolder(dimKey, custom.getId()).ifPresentOrElse(holder -> customBiomes.put(custom.getId(), holder), () -> {
+                    Iris.error("Failed to load custom biome " + dimKey + " " + custom.getId());
+                    failed.incrementAndGet();
+                });
+            }
+        }
+        if (failed.get() > 0) {
+            throw new IllegalStateException("Failed to load " + failed.get() + " custom biomes");
+        }
+
+        Registry<Biome> registry = registryAccess().registryOrThrow(Registries.BIOME);
+        minecraftBiomes = new KMap<>(org.bukkit.Registry.BIOME.stream()
+                .filter(biome -> biome != org.bukkit.block.Biome.CUSTOM)
+                .collect(Collectors.toMap(Function.identity(), b -> CraftBlock.biomeToBiomeBase(registry, b))));
+        minecraftBiomes.values().removeAll(customBiomes.values());
+    }
+
+    @Override
+    public boolean exists(int x, int z) {
+        try (IRegion region = getRegion(x >> 5, z >> 5, true)) {
+            return region != null && region.exists(x, z);
+        } catch (Exception e) {
+            return false;
+        }
+    }
+
+    @Override
+    public IRegion getRegion(int x, int z, boolean existingOnly) throws IOException {
+        AtomicReference<IOException> exception = new AtomicReference<>();
+        Region region = regions.computeIfAbsent(Cache.key(x, z), k -> {
+            trim();
+
+            try {
+                FileUtil.createDirectoriesSafe(this.folder);
+                Path path = folder.resolve("r." + x + "." + z + ".mca");
+                if (existingOnly && !Files.exists(path)) {
+                    return null;
+                } else {
+                    return new Region(path, this.folder);
+                }
+            } catch (IOException e) {
+                exception.set(e);
+                return null;
+            }
+        });
+
+        if (region == null) {
+            if (exception.get() != null)
+                throw exception.get();
+            return null;
+        }
+        region.references++;
+        return region;
+    }
+
+    @NotNull
+    @Override
+    public SerializableChunk createChunk(int x, int z) {
+        return new DirectTerrainChunk(new ProtoChunk(new ChunkPos(x, z), UpgradeData.EMPTY, this, registryAccess().registryOrThrow(Registries.BIOME), null));
+    }
+
+    @Override
+    public void fillBiomes(@NonNull SerializableChunk chunk, @Nullable ChunkContext ctx) {
+        if (!(chunk instanceof DirectTerrainChunk tc))
+            return;
+        tc.getAccess().fillBiomesFromNoise((qX, qY, qZ, sampler) -> getNoiseBiome(engine, ctx, qX << 2, qY << 2, qZ << 2), null);
+    }
+
+    @Override
+    public synchronized void close() {
+        if (closed) return;
+
+        while (!regions.isEmpty()) {
+            regions.values().removeIf(Region::remove);
+            J.sleep(1);
+        }
+
+        closed = true;
+        customBiomes.clear();
+        minecraftBiomes.clear();
+    }
+
+    private void trim() {
+        int size = regions.size();
+        if (size < 256) return;
+        int remove = size - 255;
+
+        var list = regions.values()
+                .stream()
+                .filter(Region::unused)
+                .sorted()
+                .collect(Collectors.toList())
+                .reversed();
+
+        int skip = list.size() - remove;
+        if (skip > 0) list.subList(0, skip).clear();
+
+        if (list.isEmpty()) return;
+        regions.values().removeIf(r -> list.contains(r) && r.remove());
+    }
+
+    private Holder<Biome> getNoiseBiome(Engine engine, ChunkContext ctx, int x, int y, int z) {
+        int m = y - engine.getMinHeight();
+        IrisBiome ib = ctx == null ? engine.getSurfaceBiome(x, z) : ctx.getBiome().get(x & 15, z & 15);
+        if (ib.isCustom()) {
+            return customBiomes.get(ib.getCustomBiome(biomeRng, x, m, z).getId());
+        } else {
+            return minecraftBiomes.get(ib.getSkyBiome(biomeRng, x, m, z));
+        }
+    }
+
+    static RegistryAccess registryAccess() {
+        return CACHE.aquire(() -> ((CraftServer) Bukkit.getServer()).getServer().registryAccess());
+    }
+
+    private static Optional<Holder.Reference<Biome>> biomeHolder(String namespace, String path) {
+        return registryAccess().registryOrThrow(Registries.BIOME).getHolder(ResourceKey.create(Registries.BIOME, new ResourceLocation(namespace, path)));
+    }
+
+    static CompoundTag serialize(ChunkAccess chunk) {
+        ChunkPos chunkPos = chunk.getPos();
+        CompoundTag tag = NbtUtils.addCurrentDataVersion(new CompoundTag());
+        tag.putInt("xPos", chunkPos.x);
+        tag.putInt("yPos", chunk.getMinSection());
+        tag.putInt("zPos", chunkPos.z);
+        tag.putLong("LastUpdate", 0);
+        tag.putLong("InhabitedTime", chunk.getInhabitedTime());
+        tag.putString("Status", BuiltInRegistries.CHUNK_STATUS.getKey(chunk.getStatus()).toString());
+        BlendingData blendingdata = chunk.getBlendingData();
+        if (blendingdata != null) {
+            DataResult<Tag> dataresult = BlendingData.CODEC.encodeStart(NbtOps.INSTANCE, blendingdata);
+            dataresult.resultOrPartial(LogUtils.getLogger()::error).ifPresent((nbt) -> tag.put("blending_data", nbt));
+        }
+
+        BelowZeroRetrogen retrogen = chunk.getBelowZeroRetrogen();
+        if (retrogen != null) {
+            DataResult<Tag> dataresult = BelowZeroRetrogen.CODEC.encodeStart(NbtOps.INSTANCE, retrogen);
+            dataresult.resultOrPartial(LogUtils.getLogger()::error).ifPresent((nbt) -> tag.put("below_zero_retrogen", nbt));
+        }
+
+        UpgradeData upgradeData = chunk.getUpgradeData();
+        if (!upgradeData.isEmpty()) {
+            tag.put("UpgradeData", upgradeData.write());
+        }
+
+        LevelChunkSection[] sections = chunk.getSections();
+        ListTag sectionsTag = new ListTag();
+        Registry<Biome> biomeRegistry = registryAccess().registryOrThrow(Registries.BIOME);
+        Codec<PalettedContainerRO<Holder<Biome>>> codec = PalettedContainer.codecRO(biomeRegistry.asHolderIdMap(), biomeRegistry.holderByNameCodec(), PalettedContainer.Strategy.SECTION_BIOMES, biomeRegistry.getHolderOrThrow(Biomes.PLAINS));
+        boolean flag = chunk.isLightCorrect();
+
+        int minLightSection = chunk.getMinSection() - 1;
+        int maxLightSection = minLightSection + chunk.getSectionsCount() + 2;
+        for(int y = minLightSection; y < maxLightSection; ++y) {
+            int j = chunk.getSectionIndexFromSectionY(y);
+            if (j < 0 || j >= sections.length)
+                continue;
+            CompoundTag sectionTag = new CompoundTag();
+            LevelChunkSection section = sections[j];
+            sectionTag.put("block_states", BLOCK_STATE_CODEC.encodeStart(NbtOps.INSTANCE, section.getStates()).getOrThrow(false, LogUtils.getLogger()::error));
+            sectionTag.put("biomes", codec.encodeStart(NbtOps.INSTANCE, section.getBiomes()).getOrThrow(false, LogUtils.getLogger()::error));
+
+            if (!sectionTag.isEmpty()) {
+                sectionTag.putByte("Y", (byte) y);
+                sectionsTag.add(sectionTag);
+            }
+        }
+
+        tag.put("sections", sectionsTag);
+        if (flag) {
+            tag.putBoolean("isLightOn", true);
+        }
+
+        ListTag blockEntities = new ListTag();
+        for(BlockPos blockPos : chunk.getBlockEntitiesPos()) {
+            CompoundTag entityNbt = chunk.getBlockEntityNbtForSaving(blockPos);
+            if (entityNbt != null) {
+                blockEntities.add(entityNbt);
+            }
+        }
+
+        tag.put("block_entities", blockEntities);
+        if (chunk.getStatus().getChunkType() == ChunkStatus.ChunkType.PROTOCHUNK) {
+            ProtoChunk protochunk = (ProtoChunk)chunk;
+            ListTag entities = new ListTag();
+            entities.addAll(protochunk.getEntities());
+            tag.put("entities", entities);
+            CompoundTag carvingMasks = new CompoundTag();
+
+            for(GenerationStep.Carving carving : GenerationStep.Carving.values()) {
+                CarvingMask mask = protochunk.getCarvingMask(carving);
+                if (mask != null) {
+                    carvingMasks.putLongArray(carving.toString(), mask.toArray());
+                }
+            }
+
+            tag.put("CarvingMasks", carvingMasks);
+        }
+
+        saveTicks(tag, chunk.getTicksForSerialization());
+        tag.put("PostProcessing", packOffsets(chunk.getPostProcessing()));
+        CompoundTag heightMaps = new CompoundTag();
+
+        for(Map.Entry<Heightmap.Types, Heightmap> entry : chunk.getHeightmaps()) {
+            if (chunk.getStatus().heightmapsAfter().contains(entry.getKey())) {
+                heightMaps.put(entry.getKey().getSerializationKey(), new LongArrayTag(entry.getValue().getRawData()));
+            }
+        }
+
+        tag.put("Heightmaps", heightMaps);
+
+        CompoundTag structureData = new CompoundTag();
+        structureData.put("starts", new CompoundTag());
+        structureData.put("References", new CompoundTag());
+        tag.put("structures", structureData);
+        if (!chunk.persistentDataContainer.isEmpty()) {
+            tag.put("ChunkBukkitValues", chunk.persistentDataContainer.toTagCompound());
+        }
+
+        return tag;
+    }
+
+    private static void saveTicks(CompoundTag tag, ChunkAccess.TicksToSave ticks) {
+        tag.put("block_ticks", ticks.blocks().save(0, (block) -> BuiltInRegistries.BLOCK.getKey(block).toString()));
+        tag.put("fluid_ticks", ticks.fluids().save(0, (fluid) -> BuiltInRegistries.FLUID.getKey(fluid).toString()));
+    }
+}

nms/v1_20_R2/src/main/java/com/volmit/iris/core/nms/v1_20_R2/NMSBinding.java

@@ -17,6 +17,8 @@ import com.mojang.datafixers.util.Pair;
 import com.mojang.serialization.Lifecycle;
 import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
+import com.volmit.iris.core.nms.v1_20_R2.headless.RegionStorage;
 import com.volmit.iris.util.scheduling.J;
 import lombok.SneakyThrows;
 import net.minecraft.core.*;
@@ -28,9 +30,14 @@ import net.minecraft.server.WorldLoader;
 import net.minecraft.server.commands.data.BlockDataAccessor;
 import net.minecraft.tags.TagKey;
 import net.minecraft.world.level.LevelReader;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.EntityBlock;
 import net.minecraft.world.level.dimension.DimensionType;
 import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.FlatLevelSource;
+import net.minecraft.world.level.levelgen.flat.FlatLayerInfo;
+import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
 import org.bukkit.*;
 import org.bukkit.block.Biome;
 import org.bukkit.block.data.BlockData;
@@ -640,6 +647,11 @@ public class NMSBinding implements INMSBinding {
         return registry.getHolderOrThrow(ResourceKey.create(Registries.BIOME, CraftNamespacedKey.toMinecraft(biome.getKey())));
     }
 
+    @Override
+    public IRegionStorage createRegionStorage(Engine engine) {
+        return new RegionStorage(engine);
+    }
+
     @Override
     public AutoClosing injectLevelStems() {
         return inject(this::supplier);
@@ -674,6 +686,15 @@ public class NMSBinding implements INMSBinding {
                 }));
     }
 
+    @Override
+    public boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end) {
+        var registry = registry().registryOrThrow(Registries.DIMENSION_TYPE);
+        if (overworld) overworld = !registry.containsKey(createIrisKey(LevelStem.OVERWORLD));
+        if (nether) nether = !registry.containsKey(createIrisKey(LevelStem.NETHER));
+        if (end) end = !registry.containsKey(createIrisKey(LevelStem.END));
+        return overworld || nether || end;
+    }
+
     private WorldLoader.DataLoadContext supplier(WorldLoader.DataLoadContext old) {
         return dataLoadContext.aquire(() -> new WorldLoader.DataLoadContext(
                 old.resources(),
@@ -704,23 +725,32 @@ public class NMSBinding implements INMSBinding {
     private RegistryAccess.Frozen createRegistryAccess(RegistryAccess.Frozen datapack, boolean copy, boolean overworld, boolean nether, boolean end) {
         var access = registry();
         var dimensions = access.registryOrThrow(Registries.DIMENSION_TYPE);
-        var levelStems = access.registryOrThrow(Registries.LEVEL_STEM);
 
+        var settings = new FlatLevelGeneratorSettings(
+                Optional.empty(),
+                access.lookupOrThrow(Registries.BIOME).getOrThrow(Biomes.THE_VOID),
+                List.of()
+        );
+        settings.getLayersInfo().add(new FlatLayerInfo(1, Blocks.AIR));
+        settings.updateLayers();
+
+        var source = new FlatLevelSource(settings);
         var fake = new MappedRegistry<>(Registries.LEVEL_STEM, Lifecycle.experimental());
-        if (overworld) register(fake, levelStems, dimensions, LevelStem.OVERWORLD);
+        if (overworld) register(fake, dimensions, source, LevelStem.OVERWORLD);
-        if (nether) register(fake, levelStems, dimensions, LevelStem.NETHER);
+        if (nether) register(fake, dimensions, source, LevelStem.NETHER);
-        if (end) register(fake, levelStems, dimensions, LevelStem.END);
+        if (end) register(fake, dimensions, source, LevelStem.END);
         copy(fake, datapack.registry(Registries.LEVEL_STEM).orElse(null));
 
-        if (copy) copy(fake, levelStems);
+        if (copy) copy(fake, access.registryOrThrow(Registries.LEVEL_STEM));
 
         return new RegistryAccess.Frozen.ImmutableRegistryAccess(List.of(fake.freeze())).freeze();
     }
 
-    private void register(MappedRegistry<LevelStem> target, Registry<LevelStem> levelStems, Registry<DimensionType> dimensions, ResourceKey<LevelStem> key) {
+    private void register(MappedRegistry<LevelStem> target, Registry<DimensionType> dimensions, FlatLevelSource source, ResourceKey<LevelStem> key) {
+        var loc = createIrisKey(key);
         target.register(key, new LevelStem(
-                dimensions.getHolderOrThrow(ResourceKey.create(Registries.DIMENSION_TYPE, new ResourceLocation("iris", key.location().getPath()))),
+                dimensions.getHolder(ResourceKey.create(Registries.DIMENSION_TYPE, loc)).orElseThrow(() -> new IllegalStateException("Missing dimension type " + loc + " in " + dimensions.keySet())),
-                levelStems.getOrThrow(key).generator()
+                source
         ), Lifecycle.stable());
     }
 
@@ -733,4 +763,8 @@ public class NMSBinding implements INMSBinding {
                 target.register(key, value, info);
         });
     }
+
+    private ResourceLocation createIrisKey(ResourceKey<LevelStem> key) {
+        return new ResourceLocation("iris", key.location().getPath());
+    }
 }

nms/v1_20_R2/src/main/java/com/volmit/iris/core/nms/v1_20_R2/headless/DirectTerrainChunk.java

@@ -0,0 +1,210 @@
+package com.volmit.iris.core.nms.v1_20_R2.headless;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.BiomeBaseInjector;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.util.data.IrisCustomData;
+import com.volmit.iris.util.math.Position2;
+import lombok.Data;
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.EntityBlock;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkStatus;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import org.bukkit.Material;
+import org.bukkit.block.Biome;
+import org.bukkit.block.data.BlockData;
+import org.bukkit.craftbukkit.v1_20_R2.block.CraftBiome;
+import org.bukkit.craftbukkit.v1_20_R2.block.data.CraftBlockData;
+import org.bukkit.craftbukkit.v1_20_R2.util.CraftMagicNumbers;
+import org.bukkit.generator.ChunkGenerator;
+import org.bukkit.material.MaterialData;
+import org.jetbrains.annotations.NotNull;
+
+@Data
+public final class DirectTerrainChunk implements SerializableChunk {
+    private final ProtoChunk access;
+    private final int minHeight, maxHeight;
+
+    public DirectTerrainChunk(ProtoChunk access) {
+        this.access = access;
+        this.minHeight = access.getMinBuildHeight();
+        this.maxHeight = access.getMaxBuildHeight();
+    }
+
+    @Override
+    public BiomeBaseInjector getBiomeBaseInjector() {
+        return null;
+    }
+
+    @NotNull
+    @Override
+    public Biome getBiome(int x, int z) {
+        return getBiome(x, 0, z);
+    }
+
+    @NotNull
+    @Override
+    public Biome getBiome(int x, int y, int z) {
+        if (y < minHeight || y > maxHeight) return Biome.PLAINS;
+        return CraftBiome.minecraftHolderToBukkit(access.getNoiseBiome(x >> 2, y >> 2, z >> 2));
+    }
+
+    @Override
+    public void setBiome(int x, int z, Biome bio) {
+        for (int y = minHeight; y < maxHeight; y += 4) {
+            setBiome(x, y, z, bio);
+        }
+    }
+
+    @Override
+    public void setBiome(int x, int y, int z, Biome bio) {
+        if (y < minHeight || y > maxHeight) return;
+        access.setBiome(x & 15, y, z & 15, CraftBiome.bukkitToMinecraftHolder(bio));
+    }
+
+    public void setBlock(int x, int y, int z, Material material) {
+        this.setBlock(x, y, z, material.createBlockData());
+    }
+
+    public void setBlock(int x, int y, int z, MaterialData material) {
+        this.setBlock(x, y, z, CraftMagicNumbers.getBlock(material));
+    }
+
+    @Override
+    public void setBlock(int x, int y, int z, BlockData blockData) {
+        if (blockData == null) {
+            Iris.error("NULL BD");
+        }
+        if (blockData instanceof IrisCustomData data)
+            blockData = data.getBase();
+        if (!(blockData instanceof CraftBlockData craftBlockData))
+            throw new IllegalArgumentException("Expected CraftBlockData, got " + blockData.getClass().getSimpleName() + " instead");
+        access.setBlockState(new BlockPos(x & 15, y, z & 15), craftBlockData.getState(), false);
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, Material material) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, material.createBlockData());
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, MaterialData material) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, CraftMagicNumbers.getBlock(material));
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, BlockData blockData) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, ((CraftBlockData) blockData).getState());
+    }
+
+    public Material getType(int x, int y, int z) {
+        return CraftMagicNumbers.getMaterial(this.getTypeId(x, y, z).getBlock());
+    }
+
+    public MaterialData getTypeAndData(int x, int y, int z) {
+        return CraftMagicNumbers.getMaterial(this.getTypeId(x, y, z));
+    }
+
+    public BlockData getBlockData(int x, int y, int z) {
+        return CraftBlockData.fromData(this.getTypeId(x, y, z));
+    }
+
+    @Override
+    public ChunkGenerator.ChunkData getRaw() {
+        return null;
+    }
+
+    @Override
+    public void setRaw(ChunkGenerator.ChunkData data) {
+
+    }
+
+    @Override
+    public void inject(ChunkGenerator.BiomeGrid biome) {
+
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, BlockState type) {
+        if (xMin > 15 || yMin >= this.maxHeight || zMin > 15)
+            return;
+
+        if (xMin < 0) {
+            xMin = 0;
+        }
+
+        if (yMin < this.minHeight) {
+            yMin = this.minHeight;
+        }
+
+        if (zMin < 0) {
+            zMin = 0;
+        }
+
+        if (xMax > 16) {
+            xMax = 16;
+        }
+
+        if (yMax > this.maxHeight) {
+            yMax = this.maxHeight;
+        }
+
+        if (zMax > 16) {
+            zMax = 16;
+        }
+
+        if (xMin >= xMax || yMin >= yMax || zMin >= zMax)
+            return;
+
+        for (int y = yMin; y < yMax; ++y) {
+            for (int x = xMin; x < xMax; ++x) {
+                for (int z = zMin; z < zMax; ++z) {
+                    this.setBlock(x, y, z, type);
+                }
+            }
+        }
+
+    }
+
+    public BlockState getTypeId(int x, int y, int z) {
+        if (x != (x & 15) || y < this.minHeight || y >= this.maxHeight || z != (z & 15))
+            return Blocks.AIR.defaultBlockState();
+        return access.getBlockState(new BlockPos(access.getPos().getMinBlockX() + x, y, access.getPos().getMinBlockZ() + z));
+    }
+
+    public byte getData(int x, int y, int z) {
+        return CraftMagicNumbers.toLegacyData(this.getTypeId(x, y, z));
+    }
+
+    private void setBlock(int x, int y, int z, BlockState type) {
+        if (x != (x & 15) || y < this.minHeight || y >= this.maxHeight || z != (z & 15))
+            return;
+        BlockPos blockPosition = new BlockPos(access.getPos().getMinBlockX() + x, y, access.getPos().getMinBlockZ() + z);
+        BlockState oldBlockData = access.setBlockState(blockPosition, type, false);
+        if (type.hasBlockEntity()) {
+            BlockEntity tileEntity = ((EntityBlock) type.getBlock()).newBlockEntity(blockPosition, type);
+            if (tileEntity == null) {
+                access.removeBlockEntity(blockPosition);
+            } else {
+                access.setBlockEntity(tileEntity);
+            }
+        } else if (oldBlockData != null && oldBlockData.hasBlockEntity()) {
+            access.removeBlockEntity(blockPosition);
+        }
+
+    }
+
+    @Override
+    public Position2 getPos() {
+        return new Position2(access.getPos().x, access.getPos().z);
+    }
+
+    @Override
+    public Object serialize() {
+        return RegionStorage.serialize(access);
+    }
+
+    @Override
+    public void mark() {
+        access.setStatus(ChunkStatus.FULL);
+    }
+}

nms/v1_20_R2/src/main/java/com/volmit/iris/core/nms/v1_20_R2/headless/Region.java

@@ -0,0 +1,72 @@
+package com.volmit.iris.core.nms.v1_20_R2.headless;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.headless.IRegion;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.util.math.M;
+import lombok.NonNull;
+import lombok.Synchronized;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.NbtIo;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.chunk.storage.RegionFile;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.nio.file.Path;
+
+class Region implements IRegion, Comparable<Region> {
+    private final RegionFile regionFile;
+    transient long references;
+    transient long lastUsed;
+
+    Region(Path path, Path folder) throws IOException {
+        this.regionFile = new RegionFile(path, folder, false);
+    }
+
+    @Override
+    @Synchronized
+    public boolean exists(int x, int z) {
+        try (DataInputStream din = regionFile.getChunkDataInputStream(new ChunkPos(x, z))) {
+            if (din == null) return false;
+            return !"empty".equals(NbtIo.read(din).getString("Status"));
+        } catch (IOException e) {
+            return false;
+        }
+    }
+
+    @Override
+    @Synchronized
+    public void write(@NonNull SerializableChunk chunk) throws IOException {
+        try (DataOutputStream dos = regionFile.getChunkDataOutputStream(chunk.getPos().convert(ChunkPos::new))) {
+            NbtIo.write((CompoundTag) chunk.serialize(), dos);
+        }
+    }
+
+    @Override
+    public void close() {
+        --references;
+        lastUsed = M.ms();
+    }
+
+    public boolean unused() {
+        return references <= 0;
+    }
+
+    public boolean remove() {
+        if (!unused()) return false;
+        try {
+            regionFile.close();
+        } catch (IOException e) {
+            Iris.error("Failed to close region file");
+            e.printStackTrace();
+        }
+        return true;
+    }
+
+    @Override
+    public int compareTo(Region o) {
+        return Long.compare(lastUsed, o.lastUsed);
+    }
+}

nms/v1_20_R2/src/main/java/com/volmit/iris/core/nms/v1_20_R2/headless/RegionStorage.java

@@ -0,0 +1,311 @@
+package com.volmit.iris.core.nms.v1_20_R2.headless;
+
+import com.mojang.logging.LogUtils;
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.DataResult;
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.headless.IRegion;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.engine.data.cache.AtomicCache;
+import com.volmit.iris.engine.data.cache.Cache;
+import com.volmit.iris.engine.framework.Engine;
+import com.volmit.iris.engine.object.IrisBiome;
+import com.volmit.iris.util.collection.KMap;
+import com.volmit.iris.util.context.ChunkContext;
+import com.volmit.iris.util.math.RNG;
+import com.volmit.iris.util.scheduling.J;
+import lombok.Getter;
+import lombok.NonNull;
+import net.minecraft.FileUtil;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.Registry;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.nbt.*;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.chunk.*;
+import net.minecraft.world.level.levelgen.BelowZeroRetrogen;
+import net.minecraft.world.level.levelgen.GenerationStep;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.blending.BlendingData;
+import org.bukkit.Bukkit;
+import org.bukkit.craftbukkit.v1_20_R2.CraftServer;
+import org.bukkit.craftbukkit.v1_20_R2.block.CraftBiome;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Map;
+import java.util.Optional;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+import static net.minecraft.world.level.chunk.storage.ChunkSerializer.BLOCK_STATE_CODEC;
+import static net.minecraft.world.level.chunk.storage.ChunkSerializer.packOffsets;
+
+public class RegionStorage implements IRegionStorage, LevelHeightAccessor {
+    private static final AtomicCache<RegistryAccess> CACHE = new AtomicCache<>();
+    private final KMap<Long, Region> regions = new KMap<>();
+    private final Path folder;
+
+    private final Engine engine;
+    private final KMap<String, Holder<Biome>> customBiomes = new KMap<>();
+    private final KMap<org.bukkit.block.Biome, Holder<Biome>> minecraftBiomes;
+    private final RNG biomeRng;
+    private final @Getter int minBuildHeight;
+    private final @Getter int height;
+
+    private transient boolean closed = false;
+
+    public RegionStorage(Engine engine) {
+        this.engine = engine;
+        this.folder = new File(engine.getWorld().worldFolder(), "region").toPath();
+        this.biomeRng = new RNG(engine.getSeedManager().getBiome());
+
+        this.minBuildHeight = engine.getDimension().getMinHeight();
+        this.height = engine.getDimension().getMaxHeight() - minBuildHeight;
+
+        AtomicInteger failed = new AtomicInteger();
+        var dimKey = engine.getDimension().getLoadKey();
+        for (var biome : engine.getAllBiomes()) {
+            if (!biome.isCustom()) continue;
+            for (var custom : biome.getCustomDerivitives()) {
+                biomeHolder(dimKey, custom.getId()).ifPresentOrElse(holder -> customBiomes.put(custom.getId(), holder), () -> {
+                    Iris.error("Failed to load custom biome " + dimKey + " " + custom.getId());
+                    failed.incrementAndGet();
+                });
+            }
+        }
+        if (failed.get() > 0) {
+            throw new IllegalStateException("Failed to load " + failed.get() + " custom biomes");
+        }
+
+        minecraftBiomes = new KMap<>(org.bukkit.Registry.BIOME.stream()
+                .filter(biome -> biome != org.bukkit.block.Biome.CUSTOM)
+                .collect(Collectors.toMap(Function.identity(), CraftBiome::bukkitToMinecraftHolder)));
+        minecraftBiomes.values().removeAll(customBiomes.values());
+    }
+
+    @Override
+    public boolean exists(int x, int z) {
+        try (IRegion region = getRegion(x >> 5, z >> 5, true)) {
+            return region != null && region.exists(x, z);
+        } catch (Exception e) {
+            return false;
+        }
+    }
+
+    @Override
+    public IRegion getRegion(int x, int z, boolean existingOnly) throws IOException {
+        AtomicReference<IOException> exception = new AtomicReference<>();
+        Region region = regions.computeIfAbsent(Cache.key(x, z), k -> {
+            trim();
+
+            try {
+                FileUtil.createDirectoriesSafe(this.folder);
+                Path path = folder.resolve("r." + x + "." + z + ".mca");
+                if (existingOnly && !Files.exists(path)) {
+                    return null;
+                } else {
+                    return new Region(path, this.folder);
+                }
+            } catch (IOException e) {
+                exception.set(e);
+                return null;
+            }
+        });
+
+        if (region == null) {
+            if (exception.get() != null)
+                throw exception.get();
+            return null;
+        }
+        region.references++;
+        return region;
+    }
+
+    @NotNull
+    @Override
+    public SerializableChunk createChunk(int x, int z) {
+        return new DirectTerrainChunk(new ProtoChunk(new ChunkPos(x, z), UpgradeData.EMPTY, this, registryAccess().registryOrThrow(Registries.BIOME), null));
+    }
+
+    @Override
+    public void fillBiomes(@NonNull SerializableChunk chunk, @Nullable ChunkContext ctx) {
+        if (!(chunk instanceof DirectTerrainChunk tc))
+            return;
+        tc.getAccess().fillBiomesFromNoise((qX, qY, qZ, sampler) -> getNoiseBiome(engine, ctx, qX << 2, qY << 2, qZ << 2), null);
+    }
+
+    @Override
+    public synchronized void close() {
+        if (closed) return;
+
+        while (!regions.isEmpty()) {
+            regions.values().removeIf(Region::remove);
+            J.sleep(1);
+        }
+
+        closed = true;
+        customBiomes.clear();
+        minecraftBiomes.clear();
+    }
+
+    private void trim() {
+        int size = regions.size();
+        if (size < 256) return;
+        int remove = size - 255;
+
+        var list = regions.values()
+                .stream()
+                .filter(Region::unused)
+                .sorted()
+                .collect(Collectors.toList())
+                .reversed();
+
+        int skip = list.size() - remove;
+        if (skip > 0) list.subList(0, skip).clear();
+
+        if (list.isEmpty()) return;
+        regions.values().removeIf(r -> list.contains(r) && r.remove());
+    }
+
+    private Holder<Biome> getNoiseBiome(Engine engine, ChunkContext ctx, int x, int y, int z) {
+        int m = y - engine.getMinHeight();
+        IrisBiome ib = ctx == null ? engine.getSurfaceBiome(x, z) : ctx.getBiome().get(x & 15, z & 15);
+        if (ib.isCustom()) {
+            return customBiomes.get(ib.getCustomBiome(biomeRng, x, m, z).getId());
+        } else {
+            return minecraftBiomes.get(ib.getSkyBiome(biomeRng, x, m, z));
+        }
+    }
+
+    private static RegistryAccess registryAccess() {
+        return CACHE.aquire(() -> ((CraftServer) Bukkit.getServer()).getServer().registryAccess());
+    }
+
+    private static Optional<Holder.Reference<Biome>> biomeHolder(String namespace, String path) {
+        return registryAccess().registryOrThrow(Registries.BIOME).getHolder(ResourceKey.create(Registries.BIOME, new ResourceLocation(namespace, path)));
+    }
+
+    static CompoundTag serialize(ChunkAccess chunk) {
+        ChunkPos chunkPos = chunk.getPos();
+        CompoundTag tag = NbtUtils.addCurrentDataVersion(new CompoundTag());
+        tag.putInt("xPos", chunkPos.x);
+        tag.putInt("yPos", chunk.getMinSection());
+        tag.putInt("zPos", chunkPos.z);
+        tag.putLong("LastUpdate", 0);
+        tag.putLong("InhabitedTime", chunk.getInhabitedTime());
+        tag.putString("Status", BuiltInRegistries.CHUNK_STATUS.getKey(chunk.getStatus()).toString());
+        BlendingData blendingdata = chunk.getBlendingData();
+        if (blendingdata != null) {
+            DataResult<Tag> dataresult = BlendingData.CODEC.encodeStart(NbtOps.INSTANCE, blendingdata);
+            dataresult.resultOrPartial(LogUtils.getLogger()::error).ifPresent((nbt) -> tag.put("blending_data", nbt));
+        }
+
+        BelowZeroRetrogen retrogen = chunk.getBelowZeroRetrogen();
+        if (retrogen != null) {
+            DataResult<Tag> dataresult = BelowZeroRetrogen.CODEC.encodeStart(NbtOps.INSTANCE, retrogen);
+            dataresult.resultOrPartial(LogUtils.getLogger()::error).ifPresent((nbt) -> tag.put("below_zero_retrogen", nbt));
+        }
+
+        UpgradeData upgradeData = chunk.getUpgradeData();
+        if (!upgradeData.isEmpty()) {
+            tag.put("UpgradeData", upgradeData.write());
+        }
+
+        LevelChunkSection[] sections = chunk.getSections();
+        ListTag sectionsTag = new ListTag();
+        Registry<Biome> biomeRegistry = registryAccess().registryOrThrow(Registries.BIOME);
+        Codec<PalettedContainerRO<Holder<Biome>>> codec = PalettedContainer.codecRO(biomeRegistry.asHolderIdMap(), biomeRegistry.holderByNameCodec(), PalettedContainer.Strategy.SECTION_BIOMES, biomeRegistry.getHolderOrThrow(Biomes.PLAINS));
+        boolean flag = chunk.isLightCorrect();
+
+        int minLightSection = chunk.getMinSection() - 1;
+        int maxLightSection = minLightSection + chunk.getSectionsCount() + 2;
+        for(int y = minLightSection; y < maxLightSection; ++y) {
+            int j = chunk.getSectionIndexFromSectionY(y);
+            if (j < 0 || j >= sections.length)
+                continue;
+            CompoundTag sectionTag = new CompoundTag();
+            LevelChunkSection section = sections[j];
+            sectionTag.put("block_states", BLOCK_STATE_CODEC.encodeStart(NbtOps.INSTANCE, section.getStates()).getOrThrow(false, LogUtils.getLogger()::error));
+            sectionTag.put("biomes", codec.encodeStart(NbtOps.INSTANCE, section.getBiomes()).getOrThrow(false, LogUtils.getLogger()::error));
+
+            if (!sectionTag.isEmpty()) {
+                sectionTag.putByte("Y", (byte) y);
+                sectionsTag.add(sectionTag);
+            }
+        }
+
+        tag.put("sections", sectionsTag);
+        if (flag) {
+            tag.putBoolean("isLightOn", true);
+        }
+
+        ListTag blockEntities = new ListTag();
+        for(BlockPos blockPos : chunk.getBlockEntitiesPos()) {
+            CompoundTag entityNbt = chunk.getBlockEntityNbtForSaving(blockPos);
+            if (entityNbt != null) {
+                blockEntities.add(entityNbt);
+            }
+        }
+
+        tag.put("block_entities", blockEntities);
+        if (chunk.getStatus().getChunkType() == ChunkStatus.ChunkType.PROTOCHUNK) {
+            ProtoChunk protochunk = (ProtoChunk)chunk;
+            ListTag entities = new ListTag();
+            entities.addAll(protochunk.getEntities());
+            tag.put("entities", entities);
+            CompoundTag carvingMasks = new CompoundTag();
+
+            for(GenerationStep.Carving carving : GenerationStep.Carving.values()) {
+                CarvingMask mask = protochunk.getCarvingMask(carving);
+                if (mask != null) {
+                    carvingMasks.putLongArray(carving.toString(), mask.toArray());
+                }
+            }
+
+            tag.put("CarvingMasks", carvingMasks);
+        }
+
+        saveTicks(tag, chunk.getTicksForSerialization());
+        tag.put("PostProcessing", packOffsets(chunk.getPostProcessing()));
+        CompoundTag heightMaps = new CompoundTag();
+
+        for(Map.Entry<Heightmap.Types, Heightmap> entry : chunk.getHeightmaps()) {
+            if (chunk.getStatus().heightmapsAfter().contains(entry.getKey())) {
+                heightMaps.put(entry.getKey().getSerializationKey(), new LongArrayTag(entry.getValue().getRawData()));
+            }
+        }
+
+        tag.put("Heightmaps", heightMaps);
+
+        CompoundTag structureData = new CompoundTag();
+        structureData.put("starts", new CompoundTag());
+        structureData.put("References", new CompoundTag());
+        tag.put("structures", structureData);
+        if (!chunk.persistentDataContainer.isEmpty()) {
+            tag.put("ChunkBukkitValues", chunk.persistentDataContainer.toTagCompound());
+        }
+
+        return tag;
+    }
+
+    private static void saveTicks(CompoundTag tag, ChunkAccess.TicksToSave ticks) {
+        tag.put("block_ticks", ticks.blocks().save(0, (block) -> BuiltInRegistries.BLOCK.getKey(block).toString()));
+        tag.put("fluid_ticks", ticks.fluids().save(0, (fluid) -> BuiltInRegistries.FLUID.getKey(fluid).toString()));
+    }
+}

nms/v1_20_R3/src/main/java/com/volmit/iris/core/nms/v1_20_R3/NMSBinding.java

@@ -17,6 +17,8 @@ import com.mojang.datafixers.util.Pair;
 import com.mojang.serialization.Lifecycle;
 import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
+import com.volmit.iris.core.nms.v1_20_R3.headless.RegionStorage;
 import com.volmit.iris.util.scheduling.J;
 import lombok.SneakyThrows;
 import net.minecraft.core.*;
@@ -28,9 +30,14 @@ import net.minecraft.server.WorldLoader;
 import net.minecraft.server.commands.data.BlockDataAccessor;
 import net.minecraft.tags.TagKey;
 import net.minecraft.world.level.LevelReader;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.EntityBlock;
 import net.minecraft.world.level.dimension.DimensionType;
 import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.FlatLevelSource;
+import net.minecraft.world.level.levelgen.flat.FlatLayerInfo;
+import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
 import org.bukkit.*;
 import org.bukkit.block.Biome;
 import org.bukkit.block.data.BlockData;
@@ -641,6 +648,11 @@ public class NMSBinding implements INMSBinding {
         return registry.getHolderOrThrow(ResourceKey.create(Registries.BIOME, CraftNamespacedKey.toMinecraft(biome.getKey())));
     }
 
+    @Override
+    public IRegionStorage createRegionStorage(Engine engine) {
+        return new RegionStorage(engine);
+    }
+
     @Override
     public AutoClosing injectLevelStems() {
         return inject(this::supplier);
@@ -675,6 +687,15 @@ public class NMSBinding implements INMSBinding {
                 }));
     }
 
+    @Override
+    public boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end) {
+        var registry = registry().registryOrThrow(Registries.DIMENSION_TYPE);
+        if (overworld) overworld = !registry.containsKey(createIrisKey(LevelStem.OVERWORLD));
+        if (nether) nether = !registry.containsKey(createIrisKey(LevelStem.NETHER));
+        if (end) end = !registry.containsKey(createIrisKey(LevelStem.END));
+        return overworld || nether || end;
+    }
+
     private WorldLoader.DataLoadContext supplier(WorldLoader.DataLoadContext old) {
         return dataLoadContext.aquire(() -> new WorldLoader.DataLoadContext(
                 old.resources(),
@@ -705,23 +726,32 @@ public class NMSBinding implements INMSBinding {
     private RegistryAccess.Frozen createRegistryAccess(RegistryAccess.Frozen datapack, boolean copy, boolean overworld, boolean nether, boolean end) {
         var access = registry();
         var dimensions = access.registryOrThrow(Registries.DIMENSION_TYPE);
-        var levelStems = access.registryOrThrow(Registries.LEVEL_STEM);
 
+        var settings = new FlatLevelGeneratorSettings(
+                Optional.empty(),
+                access.lookupOrThrow(Registries.BIOME).getOrThrow(Biomes.THE_VOID),
+                List.of()
+        );
+        settings.getLayersInfo().add(new FlatLayerInfo(1, Blocks.AIR));
+        settings.updateLayers();
+
+        var source = new FlatLevelSource(settings);
         var fake = new MappedRegistry<>(Registries.LEVEL_STEM, Lifecycle.experimental());
-        if (overworld) register(fake, levelStems, dimensions, LevelStem.OVERWORLD);
+        if (overworld) register(fake, dimensions, source, LevelStem.OVERWORLD);
-        if (nether) register(fake, levelStems, dimensions, LevelStem.NETHER);
+        if (nether) register(fake, dimensions, source, LevelStem.NETHER);
-        if (end) register(fake, levelStems, dimensions, LevelStem.END);
+        if (end) register(fake, dimensions, source, LevelStem.END);
         copy(fake, datapack.registry(Registries.LEVEL_STEM).orElse(null));
 
-        if (copy) copy(fake, levelStems);
+        if (copy) copy(fake, access.registryOrThrow(Registries.LEVEL_STEM));
 
         return new RegistryAccess.Frozen.ImmutableRegistryAccess(List.of(fake.freeze())).freeze();
     }
 
-    private void register(MappedRegistry<LevelStem> target, Registry<LevelStem> levelStems, Registry<DimensionType> dimensions, ResourceKey<LevelStem> key) {
+    private void register(MappedRegistry<LevelStem> target, Registry<DimensionType> dimensions, FlatLevelSource source, ResourceKey<LevelStem> key) {
+        var loc = createIrisKey(key);
         target.register(key, new LevelStem(
-                dimensions.getHolderOrThrow(ResourceKey.create(Registries.DIMENSION_TYPE, new ResourceLocation("iris", key.location().getPath()))),
+                dimensions.getHolder(ResourceKey.create(Registries.DIMENSION_TYPE, loc)).orElseThrow(() -> new IllegalStateException("Missing dimension type " + loc + " in " + dimensions.keySet())),
-                levelStems.getOrThrow(key).generator()
+                source
         ), Lifecycle.stable());
     }
 
@@ -734,4 +764,8 @@ public class NMSBinding implements INMSBinding {
                 target.register(key, value, info);
         });
     }
+
+    private ResourceLocation createIrisKey(ResourceKey<LevelStem> key) {
+        return new ResourceLocation("iris", key.location().getPath());
+    }
 }

nms/v1_20_R3/src/main/java/com/volmit/iris/core/nms/v1_20_R3/headless/DirectTerrainChunk.java

@@ -0,0 +1,211 @@
+package com.volmit.iris.core.nms.v1_20_R3.headless;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.BiomeBaseInjector;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.util.data.IrisCustomData;
+import com.volmit.iris.util.math.Position2;
+import lombok.Data;
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.EntityBlock;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkStatus;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import org.bukkit.Material;
+import org.bukkit.block.Biome;
+import org.bukkit.block.data.BlockData;
+import org.bukkit.craftbukkit.v1_20_R3.block.CraftBiome;
+import org.bukkit.craftbukkit.v1_20_R3.block.CraftBlockType;
+import org.bukkit.craftbukkit.v1_20_R3.block.data.CraftBlockData;
+import org.bukkit.craftbukkit.v1_20_R3.util.CraftMagicNumbers;
+import org.bukkit.generator.ChunkGenerator;
+import org.bukkit.material.MaterialData;
+import org.jetbrains.annotations.NotNull;
+
+@Data
+public final class DirectTerrainChunk implements SerializableChunk {
+    private final ProtoChunk access;
+    private final int minHeight, maxHeight;
+
+    public DirectTerrainChunk(ProtoChunk access) {
+        this.access = access;
+        this.minHeight = access.getMinBuildHeight();
+        this.maxHeight = access.getMaxBuildHeight();
+    }
+
+    @Override
+    public BiomeBaseInjector getBiomeBaseInjector() {
+        return null;
+    }
+
+    @NotNull
+    @Override
+    public Biome getBiome(int x, int z) {
+        return getBiome(x, 0, z);
+    }
+
+    @NotNull
+    @Override
+    public Biome getBiome(int x, int y, int z) {
+        if (y < minHeight || y > maxHeight) return Biome.PLAINS;
+        return CraftBiome.minecraftHolderToBukkit(access.getNoiseBiome(x >> 2, y >> 2, z >> 2));
+    }
+
+    @Override
+    public void setBiome(int x, int z, Biome bio) {
+        for (int y = minHeight; y < maxHeight; y += 4) {
+            setBiome(x, y, z, bio);
+        }
+    }
+
+    @Override
+    public void setBiome(int x, int y, int z, Biome bio) {
+        if (y < minHeight || y > maxHeight) return;
+        access.setBiome(x & 15, y, z & 15, CraftBiome.bukkitToMinecraftHolder(bio));
+    }
+
+    public void setBlock(int x, int y, int z, Material material) {
+        this.setBlock(x, y, z, material.createBlockData());
+    }
+
+    public void setBlock(int x, int y, int z, MaterialData material) {
+        this.setBlock(x, y, z, CraftMagicNumbers.getBlock(material));
+    }
+
+    @Override
+    public void setBlock(int x, int y, int z, BlockData blockData) {
+        if (blockData == null) {
+            Iris.error("NULL BD");
+        }
+        if (blockData instanceof IrisCustomData data)
+            blockData = data.getBase();
+        if (!(blockData instanceof CraftBlockData craftBlockData))
+            throw new IllegalArgumentException("Expected CraftBlockData, got " + blockData.getClass().getSimpleName() + " instead");
+        access.setBlockState(new BlockPos(x & 15, y, z & 15), craftBlockData.getState(), false);
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, Material material) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, material.createBlockData());
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, MaterialData material) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, CraftMagicNumbers.getBlock(material));
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, BlockData blockData) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, ((CraftBlockData) blockData).getState());
+    }
+
+    public Material getType(int x, int y, int z) {
+        return CraftBlockType.minecraftToBukkit(this.getTypeId(x, y, z).getBlock());
+    }
+
+    public MaterialData getTypeAndData(int x, int y, int z) {
+        return CraftMagicNumbers.getMaterial(this.getTypeId(x, y, z));
+    }
+
+    public BlockData getBlockData(int x, int y, int z) {
+        return CraftBlockData.fromData(this.getTypeId(x, y, z));
+    }
+
+    @Override
+    public ChunkGenerator.ChunkData getRaw() {
+        return null;
+    }
+
+    @Override
+    public void setRaw(ChunkGenerator.ChunkData data) {
+
+    }
+
+    @Override
+    public void inject(ChunkGenerator.BiomeGrid biome) {
+
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, BlockState type) {
+        if (xMin > 15 || yMin >= this.maxHeight || zMin > 15)
+            return;
+
+        if (xMin < 0) {
+            xMin = 0;
+        }
+
+        if (yMin < this.minHeight) {
+            yMin = this.minHeight;
+        }
+
+        if (zMin < 0) {
+            zMin = 0;
+        }
+
+        if (xMax > 16) {
+            xMax = 16;
+        }
+
+        if (yMax > this.maxHeight) {
+            yMax = this.maxHeight;
+        }
+
+        if (zMax > 16) {
+            zMax = 16;
+        }
+
+        if (xMin >= xMax || yMin >= yMax || zMin >= zMax)
+            return;
+
+        for (int y = yMin; y < yMax; ++y) {
+            for (int x = xMin; x < xMax; ++x) {
+                for (int z = zMin; z < zMax; ++z) {
+                    this.setBlock(x, y, z, type);
+                }
+            }
+        }
+
+    }
+
+    public BlockState getTypeId(int x, int y, int z) {
+        if (x != (x & 15) || y < this.minHeight || y >= this.maxHeight || z != (z & 15))
+            return Blocks.AIR.defaultBlockState();
+        return access.getBlockState(new BlockPos(access.getPos().getMinBlockX() + x, y, access.getPos().getMinBlockZ() + z));
+    }
+
+    public byte getData(int x, int y, int z) {
+        return CraftMagicNumbers.toLegacyData(this.getTypeId(x, y, z));
+    }
+
+    private void setBlock(int x, int y, int z, BlockState type) {
+        if (x != (x & 15) || y < this.minHeight || y >= this.maxHeight || z != (z & 15))
+            return;
+        BlockPos blockPosition = new BlockPos(access.getPos().getMinBlockX() + x, y, access.getPos().getMinBlockZ() + z);
+        BlockState oldBlockData = access.setBlockState(blockPosition, type, false);
+        if (type.hasBlockEntity()) {
+            BlockEntity tileEntity = ((EntityBlock) type.getBlock()).newBlockEntity(blockPosition, type);
+            if (tileEntity == null) {
+                access.removeBlockEntity(blockPosition);
+            } else {
+                access.setBlockEntity(tileEntity);
+            }
+        } else if (oldBlockData != null && oldBlockData.hasBlockEntity()) {
+            access.removeBlockEntity(blockPosition);
+        }
+
+    }
+
+    @Override
+    public Position2 getPos() {
+        return new Position2(access.getPos().x, access.getPos().z);
+    }
+
+    @Override
+    public Object serialize() {
+        return RegionStorage.serialize(access);
+    }
+
+    @Override
+    public void mark() {
+        access.setStatus(ChunkStatus.FULL);
+    }
+}

nms/v1_20_R3/src/main/java/com/volmit/iris/core/nms/v1_20_R3/headless/Region.java

@@ -0,0 +1,72 @@
+package com.volmit.iris.core.nms.v1_20_R3.headless;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.headless.IRegion;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.util.math.M;
+import lombok.NonNull;
+import lombok.Synchronized;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.NbtIo;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.chunk.storage.RegionFile;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.nio.file.Path;
+
+class Region implements IRegion, Comparable<Region> {
+    private final RegionFile regionFile;
+    transient long references;
+    transient long lastUsed;
+
+    Region(Path path, Path folder) throws IOException {
+        this.regionFile = new RegionFile(path, folder, false);
+    }
+
+    @Override
+    @Synchronized
+    public boolean exists(int x, int z) {
+        try (DataInputStream din = regionFile.getChunkDataInputStream(new ChunkPos(x, z))) {
+            if (din == null) return false;
+            return !"empty".equals(NbtIo.read(din).getString("Status"));
+        } catch (IOException e) {
+            return false;
+        }
+    }
+
+    @Override
+    @Synchronized
+    public void write(@NonNull SerializableChunk chunk) throws IOException {
+        try (DataOutputStream dos = regionFile.getChunkDataOutputStream(chunk.getPos().convert(ChunkPos::new))) {
+            NbtIo.write((CompoundTag) chunk.serialize(), dos);
+        }
+    }
+
+    @Override
+    public void close() {
+        --references;
+        lastUsed = M.ms();
+    }
+
+    public boolean unused() {
+        return references <= 0;
+    }
+
+    public boolean remove() {
+        if (!unused()) return false;
+        try {
+            regionFile.close();
+        } catch (IOException e) {
+            Iris.error("Failed to close region file");
+            e.printStackTrace();
+        }
+        return true;
+    }
+
+    @Override
+    public int compareTo(Region o) {
+        return Long.compare(lastUsed, o.lastUsed);
+    }
+}

nms/v1_20_R3/src/main/java/com/volmit/iris/core/nms/v1_20_R3/headless/RegionStorage.java

@@ -0,0 +1,311 @@
+package com.volmit.iris.core.nms.v1_20_R3.headless;
+
+import com.mojang.logging.LogUtils;
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.DataResult;
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.headless.IRegion;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.engine.data.cache.AtomicCache;
+import com.volmit.iris.engine.data.cache.Cache;
+import com.volmit.iris.engine.framework.Engine;
+import com.volmit.iris.engine.object.IrisBiome;
+import com.volmit.iris.util.collection.KMap;
+import com.volmit.iris.util.context.ChunkContext;
+import com.volmit.iris.util.math.RNG;
+import com.volmit.iris.util.scheduling.J;
+import lombok.Getter;
+import lombok.NonNull;
+import net.minecraft.FileUtil;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.Registry;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.nbt.*;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.chunk.*;
+import net.minecraft.world.level.levelgen.BelowZeroRetrogen;
+import net.minecraft.world.level.levelgen.GenerationStep;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.blending.BlendingData;
+import org.bukkit.Bukkit;
+import org.bukkit.craftbukkit.v1_20_R3.CraftServer;
+import org.bukkit.craftbukkit.v1_20_R3.block.CraftBiome;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Map;
+import java.util.Optional;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+import static net.minecraft.world.level.chunk.storage.ChunkSerializer.BLOCK_STATE_CODEC;
+import static net.minecraft.world.level.chunk.storage.ChunkSerializer.packOffsets;
+
+public class RegionStorage implements IRegionStorage, LevelHeightAccessor {
+    private static final AtomicCache<RegistryAccess> CACHE = new AtomicCache<>();
+    private final KMap<Long, Region> regions = new KMap<>();
+    private final Path folder;
+
+    private final Engine engine;
+    private final KMap<String, Holder<Biome>> customBiomes = new KMap<>();
+    private final KMap<org.bukkit.block.Biome, Holder<Biome>> minecraftBiomes;
+    private final RNG biomeRng;
+    private final @Getter int minBuildHeight;
+    private final @Getter int height;
+
+    private transient boolean closed = false;
+
+    public RegionStorage(Engine engine) {
+        this.engine = engine;
+        this.folder = new File(engine.getWorld().worldFolder(), "region").toPath();
+        this.biomeRng = new RNG(engine.getSeedManager().getBiome());
+
+        this.minBuildHeight = engine.getDimension().getMinHeight();
+        this.height = engine.getDimension().getMaxHeight() - minBuildHeight;
+
+        AtomicInteger failed = new AtomicInteger();
+        var dimKey = engine.getDimension().getLoadKey();
+        for (var biome : engine.getAllBiomes()) {
+            if (!biome.isCustom()) continue;
+            for (var custom : biome.getCustomDerivitives()) {
+                biomeHolder(dimKey, custom.getId()).ifPresentOrElse(holder -> customBiomes.put(custom.getId(), holder), () -> {
+                    Iris.error("Failed to load custom biome " + dimKey + " " + custom.getId());
+                    failed.incrementAndGet();
+                });
+            }
+        }
+        if (failed.get() > 0) {
+            throw new IllegalStateException("Failed to load " + failed.get() + " custom biomes");
+        }
+
+        minecraftBiomes = new KMap<>(org.bukkit.Registry.BIOME.stream()
+                .filter(biome -> biome != org.bukkit.block.Biome.CUSTOM)
+                .collect(Collectors.toMap(Function.identity(), CraftBiome::bukkitToMinecraftHolder)));
+        minecraftBiomes.values().removeAll(customBiomes.values());
+    }
+
+    @Override
+    public boolean exists(int x, int z) {
+        try (IRegion region = getRegion(x >> 5, z >> 5, true)) {
+            return region != null && region.exists(x, z);
+        } catch (Exception e) {
+            return false;
+        }
+    }
+
+    @Override
+    public IRegion getRegion(int x, int z, boolean existingOnly) throws IOException {
+        AtomicReference<IOException> exception = new AtomicReference<>();
+        Region region = regions.computeIfAbsent(Cache.key(x, z), k -> {
+            trim();
+
+            try {
+                FileUtil.createDirectoriesSafe(this.folder);
+                Path path = folder.resolve("r." + x + "." + z + ".mca");
+                if (existingOnly && !Files.exists(path)) {
+                    return null;
+                } else {
+                    return new Region(path, this.folder);
+                }
+            } catch (IOException e) {
+                exception.set(e);
+                return null;
+            }
+        });
+
+        if (region == null) {
+            if (exception.get() != null)
+                throw exception.get();
+            return null;
+        }
+        region.references++;
+        return region;
+    }
+
+    @NotNull
+    @Override
+    public SerializableChunk createChunk(int x, int z) {
+        return new DirectTerrainChunk(new ProtoChunk(new ChunkPos(x, z), UpgradeData.EMPTY, this, registryAccess().registryOrThrow(Registries.BIOME), null));
+    }
+
+    @Override
+    public void fillBiomes(@NonNull SerializableChunk chunk, @Nullable ChunkContext ctx) {
+        if (!(chunk instanceof DirectTerrainChunk tc))
+            return;
+        tc.getAccess().fillBiomesFromNoise((qX, qY, qZ, sampler) -> getNoiseBiome(engine, ctx, qX << 2, qY << 2, qZ << 2), null);
+    }
+
+    @Override
+    public synchronized void close() {
+        if (closed) return;
+
+        while (!regions.isEmpty()) {
+            regions.values().removeIf(Region::remove);
+            J.sleep(1);
+        }
+
+        closed = true;
+        customBiomes.clear();
+        minecraftBiomes.clear();
+    }
+
+    private void trim() {
+        int size = regions.size();
+        if (size < 256) return;
+        int remove = size - 255;
+
+        var list = regions.values()
+                .stream()
+                .filter(Region::unused)
+                .sorted()
+                .collect(Collectors.toList())
+                .reversed();
+
+        int skip = list.size() - remove;
+        if (skip > 0) list.subList(0, skip).clear();
+
+        if (list.isEmpty()) return;
+        regions.values().removeIf(r -> list.contains(r) && r.remove());
+    }
+
+    private Holder<Biome> getNoiseBiome(Engine engine, ChunkContext ctx, int x, int y, int z) {
+        int m = y - engine.getMinHeight();
+        IrisBiome ib = ctx == null ? engine.getSurfaceBiome(x, z) : ctx.getBiome().get(x & 15, z & 15);
+        if (ib.isCustom()) {
+            return customBiomes.get(ib.getCustomBiome(biomeRng, x, m, z).getId());
+        } else {
+            return minecraftBiomes.get(ib.getSkyBiome(biomeRng, x, m, z));
+        }
+    }
+
+    private static RegistryAccess registryAccess() {
+        return CACHE.aquire(() -> ((CraftServer) Bukkit.getServer()).getServer().registryAccess());
+    }
+
+    private static Optional<Holder.Reference<Biome>> biomeHolder(String namespace, String path) {
+        return registryAccess().registryOrThrow(Registries.BIOME).getHolder(ResourceKey.create(Registries.BIOME, new ResourceLocation(namespace, path)));
+    }
+
+    static CompoundTag serialize(ChunkAccess chunk) {
+        ChunkPos chunkPos = chunk.getPos();
+        CompoundTag tag = NbtUtils.addCurrentDataVersion(new CompoundTag());
+        tag.putInt("xPos", chunkPos.x);
+        tag.putInt("yPos", chunk.getMinSection());
+        tag.putInt("zPos", chunkPos.z);
+        tag.putLong("LastUpdate", 0);
+        tag.putLong("InhabitedTime", chunk.getInhabitedTime());
+        tag.putString("Status", BuiltInRegistries.CHUNK_STATUS.getKey(chunk.getStatus()).toString());
+        BlendingData blendingdata = chunk.getBlendingData();
+        if (blendingdata != null) {
+            DataResult<Tag> dataresult = BlendingData.CODEC.encodeStart(NbtOps.INSTANCE, blendingdata);
+            dataresult.resultOrPartial(LogUtils.getLogger()::error).ifPresent((nbt) -> tag.put("blending_data", nbt));
+        }
+
+        BelowZeroRetrogen retrogen = chunk.getBelowZeroRetrogen();
+        if (retrogen != null) {
+            DataResult<Tag> dataresult = BelowZeroRetrogen.CODEC.encodeStart(NbtOps.INSTANCE, retrogen);
+            dataresult.resultOrPartial(LogUtils.getLogger()::error).ifPresent((nbt) -> tag.put("below_zero_retrogen", nbt));
+        }
+
+        UpgradeData upgradeData = chunk.getUpgradeData();
+        if (!upgradeData.isEmpty()) {
+            tag.put("UpgradeData", upgradeData.write());
+        }
+
+        LevelChunkSection[] sections = chunk.getSections();
+        ListTag sectionsTag = new ListTag();
+        Registry<Biome> biomeRegistry = registryAccess().registryOrThrow(Registries.BIOME);
+        Codec<PalettedContainerRO<Holder<Biome>>> codec = PalettedContainer.codecRO(biomeRegistry.asHolderIdMap(), biomeRegistry.holderByNameCodec(), PalettedContainer.Strategy.SECTION_BIOMES, biomeRegistry.getHolderOrThrow(Biomes.PLAINS));
+        boolean flag = chunk.isLightCorrect();
+
+        int minLightSection = chunk.getMinSection() - 1;
+        int maxLightSection = minLightSection + chunk.getSectionsCount() + 2;
+        for(int y = minLightSection; y < maxLightSection; ++y) {
+            int j = chunk.getSectionIndexFromSectionY(y);
+            if (j < 0 || j >= sections.length)
+                continue;
+            CompoundTag sectionTag = new CompoundTag();
+            LevelChunkSection section = sections[j];
+            sectionTag.put("block_states", BLOCK_STATE_CODEC.encodeStart(NbtOps.INSTANCE, section.getStates()).getOrThrow(false, LogUtils.getLogger()::error));
+            sectionTag.put("biomes", codec.encodeStart(NbtOps.INSTANCE, section.getBiomes()).getOrThrow(false, LogUtils.getLogger()::error));
+
+            if (!sectionTag.isEmpty()) {
+                sectionTag.putByte("Y", (byte) y);
+                sectionsTag.add(sectionTag);
+            }
+        }
+
+        tag.put("sections", sectionsTag);
+        if (flag) {
+            tag.putBoolean("isLightOn", true);
+        }
+
+        ListTag blockEntities = new ListTag();
+        for(BlockPos blockPos : chunk.getBlockEntitiesPos()) {
+            CompoundTag entityNbt = chunk.getBlockEntityNbtForSaving(blockPos);
+            if (entityNbt != null) {
+                blockEntities.add(entityNbt);
+            }
+        }
+
+        tag.put("block_entities", blockEntities);
+        if (chunk.getStatus().getChunkType() == ChunkStatus.ChunkType.PROTOCHUNK) {
+            ProtoChunk protochunk = (ProtoChunk)chunk;
+            ListTag entities = new ListTag();
+            entities.addAll(protochunk.getEntities());
+            tag.put("entities", entities);
+            CompoundTag carvingMasks = new CompoundTag();
+
+            for(GenerationStep.Carving carving : GenerationStep.Carving.values()) {
+                CarvingMask mask = protochunk.getCarvingMask(carving);
+                if (mask != null) {
+                    carvingMasks.putLongArray(carving.toString(), mask.toArray());
+                }
+            }
+
+            tag.put("CarvingMasks", carvingMasks);
+        }
+
+        saveTicks(tag, chunk.getTicksForSerialization());
+        tag.put("PostProcessing", packOffsets(chunk.getPostProcessing()));
+        CompoundTag heightMaps = new CompoundTag();
+
+        for(Map.Entry<Heightmap.Types, Heightmap> entry : chunk.getHeightmaps()) {
+            if (chunk.getStatus().heightmapsAfter().contains(entry.getKey())) {
+                heightMaps.put(entry.getKey().getSerializationKey(), new LongArrayTag(entry.getValue().getRawData()));
+            }
+        }
+
+        tag.put("Heightmaps", heightMaps);
+
+        CompoundTag structureData = new CompoundTag();
+        structureData.put("starts", new CompoundTag());
+        structureData.put("References", new CompoundTag());
+        tag.put("structures", structureData);
+        if (!chunk.persistentDataContainer.isEmpty()) {
+            tag.put("ChunkBukkitValues", chunk.persistentDataContainer.toTagCompound());
+        }
+
+        return tag;
+    }
+
+    private static void saveTicks(CompoundTag tag, ChunkAccess.TicksToSave ticks) {
+        tag.put("block_ticks", ticks.blocks().save(0, (block) -> BuiltInRegistries.BLOCK.getKey(block).toString()));
+        tag.put("fluid_ticks", ticks.fluids().save(0, (fluid) -> BuiltInRegistries.FLUID.getKey(fluid).toString()));
+    }
+}

nms/v1_20_R4/src/main/java/com/volmit/iris/core/nms/v1_20_R4/NMSBinding.java

@@ -14,6 +14,8 @@ import com.mojang.serialization.Lifecycle;
 import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
 import com.volmit.iris.core.nms.datapack.DataVersion;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
+import com.volmit.iris.core.nms.v1_20_R4.headless.RegionStorage;
 import com.volmit.iris.util.nbt.tag.CompoundTag;
 import com.volmit.iris.util.scheduling.J;
 import lombok.SneakyThrows;
@@ -38,11 +40,16 @@ import net.minecraft.server.level.ServerLevel;
 import net.minecraft.tags.TagKey;
 import net.minecraft.world.item.component.CustomData;
 import net.minecraft.world.level.LevelReader;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.EntityBlock;
 import net.minecraft.world.level.block.entity.BlockEntityType;
 import net.minecraft.world.level.chunk.status.ChunkStatus;
 import net.minecraft.world.level.dimension.DimensionType;
 import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.FlatLevelSource;
+import net.minecraft.world.level.levelgen.flat.FlatLayerInfo;
+import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
 import org.bukkit.*;
 import org.bukkit.block.Biome;
 import org.bukkit.block.data.BlockData;
@@ -666,6 +673,11 @@ public class NMSBinding implements INMSBinding {
         return keys;
     }
 
+    @Override
+    public IRegionStorage createRegionStorage(Engine engine) {
+        return new RegionStorage(engine);
+    }
+
     @Override
     public AutoClosing injectLevelStems() {
         return inject(this::supplier);
@@ -700,6 +712,15 @@ public class NMSBinding implements INMSBinding {
                 }));
     }
 
+    @Override
+    public boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end) {
+        var registry = registry().registryOrThrow(Registries.DIMENSION_TYPE);
+        if (overworld) overworld = !registry.containsKey(createIrisKey(LevelStem.OVERWORLD));
+        if (nether) nether = !registry.containsKey(createIrisKey(LevelStem.NETHER));
+        if (end) end = !registry.containsKey(createIrisKey(LevelStem.END));
+        return overworld || nether || end;
+    }
+
     private WorldLoader.DataLoadContext supplier(WorldLoader.DataLoadContext old) {
         return dataLoadContext.aquire(() -> new WorldLoader.DataLoadContext(
                 old.resources(),
@@ -730,23 +751,32 @@ public class NMSBinding implements INMSBinding {
     private RegistryAccess.Frozen createRegistryAccess(RegistryAccess.Frozen datapack, boolean copy, boolean overworld, boolean nether, boolean end) {
         var access = registry();
         var dimensions = access.registryOrThrow(Registries.DIMENSION_TYPE);
-        var levelStems = access.registryOrThrow(Registries.LEVEL_STEM);
 
+        var settings = new FlatLevelGeneratorSettings(
+                Optional.empty(),
+                access.lookupOrThrow(Registries.BIOME).getOrThrow(Biomes.THE_VOID),
+                List.of()
+        );
+        settings.getLayersInfo().add(new FlatLayerInfo(1, Blocks.AIR));
+        settings.updateLayers();
+
+        var source = new FlatLevelSource(settings);
         var fake = new MappedRegistry<>(Registries.LEVEL_STEM, Lifecycle.experimental());
-        if (overworld) register(fake, levelStems, dimensions, LevelStem.OVERWORLD);
+        if (overworld) register(fake, dimensions, source, LevelStem.OVERWORLD);
-        if (nether) register(fake, levelStems, dimensions, LevelStem.NETHER);
+        if (nether) register(fake, dimensions, source, LevelStem.NETHER);
-        if (end) register(fake, levelStems, dimensions, LevelStem.END);
+        if (end) register(fake, dimensions, source, LevelStem.END);
         copy(fake, datapack.registry(Registries.LEVEL_STEM).orElse(null));
 
-        if (copy) copy(fake, levelStems);
+        if (copy) copy(fake, access.registryOrThrow(Registries.LEVEL_STEM));
 
         return new RegistryAccess.Frozen.ImmutableRegistryAccess(List.of(fake.freeze())).freeze();
     }
 
-    private void register(MappedRegistry<LevelStem> target, Registry<LevelStem> levelStems, Registry<DimensionType> dimensions, ResourceKey<LevelStem> key) {
+    private void register(MappedRegistry<LevelStem> target, Registry<DimensionType> dimensions, FlatLevelSource source, ResourceKey<LevelStem> key) {
+        var loc = createIrisKey(key);
         target.register(key, new LevelStem(
-                dimensions.getHolder(new ResourceLocation("iris", key.location().getPath())).orElseThrow(),
+                dimensions.getHolder(ResourceKey.create(Registries.DIMENSION_TYPE, loc)).orElseThrow(() -> new IllegalStateException("Missing dimension type " + loc + " in " + dimensions.keySet())),
-                levelStems.getOrThrow(key).generator()
+                source
         ), RegistrationInfo.BUILT_IN);
     }
 
@@ -759,4 +789,8 @@ public class NMSBinding implements INMSBinding {
                 target.register(key, value, info);
         });
     }
+
+    private ResourceLocation createIrisKey(ResourceKey<LevelStem> key) {
+        return new ResourceLocation("iris", key.location().getPath());
+    }
 }

nms/v1_20_R4/src/main/java/com/volmit/iris/core/nms/v1_20_R4/headless/DirectTerrainChunk.java

@@ -0,0 +1,211 @@
+package com.volmit.iris.core.nms.v1_20_R4.headless;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.BiomeBaseInjector;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.util.data.IrisCustomData;
+import com.volmit.iris.util.math.Position2;
+import lombok.Data;
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.EntityBlock;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import org.bukkit.Material;
+import org.bukkit.block.Biome;
+import org.bukkit.block.data.BlockData;
+import org.bukkit.craftbukkit.v1_20_R4.block.CraftBiome;
+import org.bukkit.craftbukkit.v1_20_R4.block.CraftBlockType;
+import org.bukkit.craftbukkit.v1_20_R4.block.data.CraftBlockData;
+import org.bukkit.craftbukkit.v1_20_R4.util.CraftMagicNumbers;
+import org.bukkit.generator.ChunkGenerator;
+import org.bukkit.material.MaterialData;
+import org.jetbrains.annotations.NotNull;
+
+@Data
+public final class DirectTerrainChunk implements SerializableChunk {
+    private final ProtoChunk access;
+    private final int minHeight, maxHeight;
+
+    public DirectTerrainChunk(ProtoChunk access) {
+        this.access = access;
+        this.minHeight = access.getMinBuildHeight();
+        this.maxHeight = access.getMaxBuildHeight();
+    }
+
+    @Override
+    public BiomeBaseInjector getBiomeBaseInjector() {
+        return null;
+    }
+
+    @NotNull
+    @Override
+    public Biome getBiome(int x, int z) {
+        return getBiome(x, 0, z);
+    }
+
+    @NotNull
+    @Override
+    public Biome getBiome(int x, int y, int z) {
+        if (y < minHeight || y > maxHeight) return Biome.PLAINS;
+        return CraftBiome.minecraftHolderToBukkit(access.getNoiseBiome(x >> 2, y >> 2, z >> 2));
+    }
+
+    @Override
+    public void setBiome(int x, int z, Biome bio) {
+        for (int y = minHeight; y < maxHeight; y += 4) {
+            setBiome(x, y, z, bio);
+        }
+    }
+
+    @Override
+    public void setBiome(int x, int y, int z, Biome bio) {
+        if (y < minHeight || y > maxHeight) return;
+        access.setBiome(x & 15, y, z & 15, CraftBiome.bukkitToMinecraftHolder(bio));
+    }
+
+    public void setBlock(int x, int y, int z, Material material) {
+        this.setBlock(x, y, z, material.createBlockData());
+    }
+
+    public void setBlock(int x, int y, int z, MaterialData material) {
+        this.setBlock(x, y, z, CraftMagicNumbers.getBlock(material));
+    }
+
+    @Override
+    public void setBlock(int x, int y, int z, BlockData blockData) {
+        if (blockData == null) {
+            Iris.error("NULL BD");
+        }
+        if (blockData instanceof IrisCustomData data)
+            blockData = data.getBase();
+        if (!(blockData instanceof CraftBlockData craftBlockData))
+            throw new IllegalArgumentException("Expected CraftBlockData, got " + blockData.getClass().getSimpleName() + " instead");
+        access.setBlockState(new BlockPos(x & 15, y, z & 15), craftBlockData.getState(), false);
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, Material material) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, material.createBlockData());
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, MaterialData material) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, CraftMagicNumbers.getBlock(material));
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, BlockData blockData) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, ((CraftBlockData) blockData).getState());
+    }
+
+    public Material getType(int x, int y, int z) {
+        return CraftBlockType.minecraftToBukkit(this.getTypeId(x, y, z).getBlock());
+    }
+
+    public MaterialData getTypeAndData(int x, int y, int z) {
+        return CraftMagicNumbers.getMaterial(this.getTypeId(x, y, z));
+    }
+
+    public BlockData getBlockData(int x, int y, int z) {
+        return CraftBlockData.fromData(this.getTypeId(x, y, z));
+    }
+
+    @Override
+    public ChunkGenerator.ChunkData getRaw() {
+        return null;
+    }
+
+    @Override
+    public void setRaw(ChunkGenerator.ChunkData data) {
+
+    }
+
+    @Override
+    public void inject(ChunkGenerator.BiomeGrid biome) {
+
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, BlockState type) {
+        if (xMin > 15 || yMin >= this.maxHeight || zMin > 15)
+            return;
+
+        if (xMin < 0) {
+            xMin = 0;
+        }
+
+        if (yMin < this.minHeight) {
+            yMin = this.minHeight;
+        }
+
+        if (zMin < 0) {
+            zMin = 0;
+        }
+
+        if (xMax > 16) {
+            xMax = 16;
+        }
+
+        if (yMax > this.maxHeight) {
+            yMax = this.maxHeight;
+        }
+
+        if (zMax > 16) {
+            zMax = 16;
+        }
+
+        if (xMin >= xMax || yMin >= yMax || zMin >= zMax)
+            return;
+
+        for (int y = yMin; y < yMax; ++y) {
+            for (int x = xMin; x < xMax; ++x) {
+                for (int z = zMin; z < zMax; ++z) {
+                    this.setBlock(x, y, z, type);
+                }
+            }
+        }
+
+    }
+
+    public BlockState getTypeId(int x, int y, int z) {
+        if (x != (x & 15) || y < this.minHeight || y >= this.maxHeight || z != (z & 15))
+            return Blocks.AIR.defaultBlockState();
+        return access.getBlockState(new BlockPos(access.getPos().getMinBlockX() + x, y, access.getPos().getMinBlockZ() + z));
+    }
+
+    public byte getData(int x, int y, int z) {
+        return CraftMagicNumbers.toLegacyData(this.getTypeId(x, y, z));
+    }
+
+    private void setBlock(int x, int y, int z, BlockState type) {
+        if (x != (x & 15) || y < this.minHeight || y >= this.maxHeight || z != (z & 15))
+            return;
+        BlockPos blockPosition = new BlockPos(access.getPos().getMinBlockX() + x, y, access.getPos().getMinBlockZ() + z);
+        BlockState oldBlockData = access.setBlockState(blockPosition, type, false);
+        if (type.hasBlockEntity()) {
+            BlockEntity tileEntity = ((EntityBlock) type.getBlock()).newBlockEntity(blockPosition, type);
+            if (tileEntity == null) {
+                access.removeBlockEntity(blockPosition);
+            } else {
+                access.setBlockEntity(tileEntity);
+            }
+        } else if (oldBlockData != null && oldBlockData.hasBlockEntity()) {
+            access.removeBlockEntity(blockPosition);
+        }
+
+    }
+
+    @Override
+    public Position2 getPos() {
+        return new Position2(access.getPos().x, access.getPos().z);
+    }
+
+    @Override
+    public Object serialize() {
+        return RegionStorage.serialize(access);
+    }
+
+    @Override
+    public void mark() {
+        access.setStatus(ChunkStatus.FULL);
+    }
+}

nms/v1_20_R4/src/main/java/com/volmit/iris/core/nms/v1_20_R4/headless/Region.java

@@ -0,0 +1,75 @@
+package com.volmit.iris.core.nms.v1_20_R4.headless;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.headless.IRegion;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.util.math.M;
+import lombok.NonNull;
+import lombok.Synchronized;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.NbtIo;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.chunk.storage.RegionFile;
+import net.minecraft.world.level.chunk.storage.RegionStorageInfo;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.nio.file.Path;
+
+class Region implements IRegion, Comparable<Region> {
+    private static final RegionStorageInfo info = new RegionStorageInfo("headless", Level.OVERWORLD, "headless");
+    private final RegionFile regionFile;
+    transient long references;
+    transient long lastUsed;
+
+    Region(Path path, Path folder) throws IOException {
+        this.regionFile = new RegionFile(info, path, folder, false);
+    }
+
+    @Override
+    @Synchronized
+    public boolean exists(int x, int z) {
+        try (DataInputStream din = regionFile.getChunkDataInputStream(new ChunkPos(x, z))) {
+            if (din == null) return false;
+            return !"empty".equals(NbtIo.read(din).getString("Status"));
+        } catch (IOException e) {
+            return false;
+        }
+    }
+
+    @Override
+    @Synchronized
+    public void write(@NonNull SerializableChunk chunk) throws IOException {
+        try (DataOutputStream dos = regionFile.getChunkDataOutputStream(chunk.getPos().convert(ChunkPos::new))) {
+            NbtIo.write((CompoundTag) chunk.serialize(), dos);
+        }
+    }
+
+    @Override
+    public void close() {
+        --references;
+        lastUsed = M.ms();
+    }
+
+    public boolean unused() {
+        return references <= 0;
+    }
+
+    public boolean remove() {
+        if (!unused()) return false;
+        try {
+            regionFile.close();
+        } catch (IOException e) {
+            Iris.error("Failed to close region file");
+            e.printStackTrace();
+        }
+        return true;
+    }
+
+    @Override
+    public int compareTo(Region o) {
+        return Long.compare(lastUsed, o.lastUsed);
+    }
+}

nms/v1_20_R4/src/main/java/com/volmit/iris/core/nms/v1_20_R4/headless/RegionStorage.java

@@ -0,0 +1,311 @@
+package com.volmit.iris.core.nms.v1_20_R4.headless;
+
+import com.mojang.logging.LogUtils;
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.DataResult;
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.headless.IRegion;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.engine.data.cache.AtomicCache;
+import com.volmit.iris.engine.data.cache.Cache;
+import com.volmit.iris.engine.framework.Engine;
+import com.volmit.iris.engine.object.IrisBiome;
+import com.volmit.iris.util.collection.KMap;
+import com.volmit.iris.util.context.ChunkContext;
+import com.volmit.iris.util.math.RNG;
+import com.volmit.iris.util.scheduling.J;
+import lombok.Getter;
+import lombok.NonNull;
+import net.minecraft.FileUtil;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.Registry;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.nbt.*;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.chunk.*;
+import net.minecraft.world.level.chunk.status.ChunkType;
+import net.minecraft.world.level.levelgen.BelowZeroRetrogen;
+import net.minecraft.world.level.levelgen.GenerationStep;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.blending.BlendingData;
+import org.bukkit.Bukkit;
+import org.bukkit.craftbukkit.v1_20_R4.CraftServer;
+import org.bukkit.craftbukkit.v1_20_R4.block.CraftBiome;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Map;
+import java.util.Optional;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+import static net.minecraft.world.level.chunk.storage.ChunkSerializer.BLOCK_STATE_CODEC;
+import static net.minecraft.world.level.chunk.storage.ChunkSerializer.packOffsets;
+
+public class RegionStorage implements IRegionStorage, LevelHeightAccessor {
+    private static final AtomicCache<RegistryAccess> CACHE = new AtomicCache<>();
+    private final KMap<Long, Region> regions = new KMap<>();
+    private final Path folder;
+
+    private final Engine engine;
+    private final KMap<String, Holder<Biome>> customBiomes = new KMap<>();
+    private final KMap<org.bukkit.block.Biome, Holder<Biome>> minecraftBiomes;
+    private final RNG biomeRng;
+    private final @Getter int minBuildHeight;
+    private final @Getter int height;
+
+    private transient boolean closed = false;
+
+    public RegionStorage(Engine engine) {
+        this.engine = engine;
+        this.folder = new File(engine.getWorld().worldFolder(), "region").toPath();
+        this.biomeRng = new RNG(engine.getSeedManager().getBiome());
+
+        this.minBuildHeight = engine.getDimension().getMinHeight();
+        this.height = engine.getDimension().getMaxHeight() - minBuildHeight;
+
+        AtomicInteger failed = new AtomicInteger();
+        var dimKey = engine.getDimension().getLoadKey();
+        for (var biome : engine.getAllBiomes()) {
+            if (!biome.isCustom()) continue;
+            for (var custom : biome.getCustomDerivitives()) {
+                biomeHolder(dimKey, custom.getId()).ifPresentOrElse(holder -> customBiomes.put(custom.getId(), holder), () -> {
+                    Iris.error("Failed to load custom biome " + dimKey + " " + custom.getId());
+                    failed.incrementAndGet();
+                });
+            }
+        }
+        if (failed.get() > 0) {
+            throw new IllegalStateException("Failed to load " + failed.get() + " custom biomes");
+        }
+
+        minecraftBiomes = new KMap<>(org.bukkit.Registry.BIOME.stream()
+                .filter(biome -> biome != org.bukkit.block.Biome.CUSTOM)
+                .collect(Collectors.toMap(Function.identity(), CraftBiome::bukkitToMinecraftHolder)));
+        minecraftBiomes.values().removeAll(customBiomes.values());
+    }
+
+    @Override
+    public boolean exists(int x, int z) {
+        try (IRegion region = getRegion(x >> 5, z >> 5, true)) {
+            return region != null && region.exists(x, z);
+        } catch (Exception e) {
+            return false;
+        }
+    }
+
+    @Override
+    public IRegion getRegion(int x, int z, boolean existingOnly) throws IOException {
+        AtomicReference<IOException> exception = new AtomicReference<>();
+        Region region = regions.computeIfAbsent(Cache.key(x, z), k -> {
+            trim();
+
+            try {
+                FileUtil.createDirectoriesSafe(this.folder);
+                Path path = folder.resolve("r." + x + "." + z + ".mca");
+                if (existingOnly && !Files.exists(path)) {
+                    return null;
+                } else {
+                    return new Region(path, this.folder);
+                }
+            } catch (IOException e) {
+                exception.set(e);
+                return null;
+            }
+        });
+
+        if (region == null) {
+            if (exception.get() != null)
+                throw exception.get();
+            return null;
+        }
+        region.references++;
+        return region;
+    }
+
+    @NotNull
+    @Override
+    public SerializableChunk createChunk(int x, int z) {
+        return new DirectTerrainChunk(new ProtoChunk(new ChunkPos(x, z), UpgradeData.EMPTY, this, registryAccess().registryOrThrow(Registries.BIOME), null));
+    }
+
+    @Override
+    public void fillBiomes(@NonNull SerializableChunk chunk, @Nullable ChunkContext ctx) {
+        if (!(chunk instanceof DirectTerrainChunk tc))
+            return;
+        tc.getAccess().fillBiomesFromNoise((qX, qY, qZ, sampler) -> getNoiseBiome(engine, ctx, qX << 2, qY << 2, qZ << 2), null);
+    }
+
+    @Override
+    public synchronized void close() {
+        if (closed) return;
+
+        while (!regions.isEmpty()) {
+            regions.values().removeIf(Region::remove);
+            J.sleep(1);
+        }
+
+        closed = true;
+        customBiomes.clear();
+        minecraftBiomes.clear();
+    }
+
+    private void trim() {
+        int size = regions.size();
+        if (size < 256) return;
+        int remove = size - 255;
+
+        var list = regions.values()
+                .stream()
+                .filter(Region::unused)
+                .sorted()
+                .collect(Collectors.toList())
+                .reversed();
+
+        int skip = list.size() - remove;
+        if (skip > 0) list.subList(0, skip).clear();
+
+        if (list.isEmpty()) return;
+        regions.values().removeIf(r -> list.contains(r) && r.remove());
+    }
+
+    private Holder<Biome> getNoiseBiome(Engine engine, ChunkContext ctx, int x, int y, int z) {
+        int m = y - engine.getMinHeight();
+        IrisBiome ib = ctx == null ? engine.getSurfaceBiome(x, z) : ctx.getBiome().get(x & 15, z & 15);
+        if (ib.isCustom()) {
+            return customBiomes.get(ib.getCustomBiome(biomeRng, x, m, z).getId());
+        } else {
+            return minecraftBiomes.get(ib.getSkyBiome(biomeRng, x, m, z));
+        }
+    }
+
+    private static RegistryAccess registryAccess() {
+        return CACHE.aquire(() -> ((CraftServer) Bukkit.getServer()).getServer().registryAccess());
+    }
+
+    private static Optional<Holder.Reference<Biome>> biomeHolder(String namespace, String path) {
+        return registryAccess().registryOrThrow(Registries.BIOME).getHolder(new ResourceLocation(namespace, path));
+    }
+
+    static CompoundTag serialize(ChunkAccess chunk) {
+        ChunkPos chunkPos = chunk.getPos();
+        CompoundTag tag = NbtUtils.addCurrentDataVersion(new CompoundTag());
+        tag.putInt("xPos", chunkPos.x);
+        tag.putInt("yPos", chunk.getMinSection());
+        tag.putInt("zPos", chunkPos.z);
+        tag.putLong("LastUpdate", 0);
+        tag.putLong("InhabitedTime", chunk.getInhabitedTime());
+        tag.putString("Status", BuiltInRegistries.CHUNK_STATUS.getKey(chunk.getStatus()).toString());
+        BlendingData blendingdata = chunk.getBlendingData();
+        if (blendingdata != null) {
+            DataResult<Tag> dataresult = BlendingData.CODEC.encodeStart(NbtOps.INSTANCE, blendingdata);
+            dataresult.resultOrPartial(LogUtils.getLogger()::error).ifPresent((nbt) -> tag.put("blending_data", nbt));
+        }
+
+        BelowZeroRetrogen retrogen = chunk.getBelowZeroRetrogen();
+        if (retrogen != null) {
+            DataResult<Tag> dataresult = BelowZeroRetrogen.CODEC.encodeStart(NbtOps.INSTANCE, retrogen);
+            dataresult.resultOrPartial(LogUtils.getLogger()::error).ifPresent((nbt) -> tag.put("below_zero_retrogen", nbt));
+        }
+
+        UpgradeData upgradeData = chunk.getUpgradeData();
+        if (!upgradeData.isEmpty()) {
+            tag.put("UpgradeData", upgradeData.write());
+        }
+
+        LevelChunkSection[] sections = chunk.getSections();
+        ListTag sectionsTag = new ListTag();
+        Registry<Biome> biomeRegistry = registryAccess().registryOrThrow(Registries.BIOME);
+        Codec<PalettedContainerRO<Holder<Biome>>> codec = PalettedContainer.codecRO(biomeRegistry.asHolderIdMap(), biomeRegistry.holderByNameCodec(), PalettedContainer.Strategy.SECTION_BIOMES, biomeRegistry.getHolderOrThrow(Biomes.PLAINS));
+        boolean flag = chunk.isLightCorrect();
+
+        int minLightSection = chunk.getMinSection() - 1;
+        int maxLightSection = minLightSection + chunk.getSectionsCount() + 2;
+        for(int y = minLightSection; y < maxLightSection; ++y) {
+            int j = chunk.getSectionIndexFromSectionY(y);
+            if (j < 0 || j >= sections.length)
+                continue;
+            CompoundTag sectionTag = new CompoundTag();
+            LevelChunkSection section = sections[j];
+            sectionTag.put("block_states", BLOCK_STATE_CODEC.encodeStart(NbtOps.INSTANCE, section.getStates()).getOrThrow());
+            sectionTag.put("biomes", codec.encodeStart(NbtOps.INSTANCE, section.getBiomes()).getOrThrow());
+
+            if (!sectionTag.isEmpty()) {
+                sectionTag.putByte("Y", (byte) y);
+                sectionsTag.add(sectionTag);
+            }
+        }
+
+        tag.put("sections", sectionsTag);
+        if (flag) {
+            tag.putBoolean("isLightOn", true);
+        }
+
+        ListTag blockEntities = new ListTag();
+        for(BlockPos blockPos : chunk.getBlockEntitiesPos()) {
+            CompoundTag entityNbt = chunk.getBlockEntityNbtForSaving(blockPos, registryAccess());
+            if (entityNbt != null) {
+                blockEntities.add(entityNbt);
+            }
+        }
+
+        tag.put("block_entities", blockEntities);
+        if (chunk.getStatus().getChunkType() == ChunkType.PROTOCHUNK) {
+            ProtoChunk protochunk = (ProtoChunk)chunk;
+            ListTag entities = new ListTag();
+            entities.addAll(protochunk.getEntities());
+            tag.put("entities", entities);
+            CompoundTag carvingMasks = new CompoundTag();
+
+            for(GenerationStep.Carving carving : GenerationStep.Carving.values()) {
+                CarvingMask mask = protochunk.getCarvingMask(carving);
+                if (mask != null) {
+                    carvingMasks.putLongArray(carving.toString(), mask.toArray());
+                }
+            }
+
+            tag.put("CarvingMasks", carvingMasks);
+        }
+
+        saveTicks(tag, chunk.getTicksForSerialization());
+        tag.put("PostProcessing", packOffsets(chunk.getPostProcessing()));
+        CompoundTag heightMaps = new CompoundTag();
+
+        for(Map.Entry<Heightmap.Types, Heightmap> entry : chunk.getHeightmaps()) {
+            if (chunk.getStatus().heightmapsAfter().contains(entry.getKey())) {
+                heightMaps.put(entry.getKey().getSerializationKey(), new LongArrayTag(entry.getValue().getRawData()));
+            }
+        }
+
+        tag.put("Heightmaps", heightMaps);
+
+        CompoundTag structureData = new CompoundTag();
+        structureData.put("starts", new CompoundTag());
+        structureData.put("References", new CompoundTag());
+        tag.put("structures", structureData);
+        if (!chunk.persistentDataContainer.isEmpty()) {
+            tag.put("ChunkBukkitValues", chunk.persistentDataContainer.toTagCompound());
+        }
+
+        return tag;
+    }
+
+    private static void saveTicks(CompoundTag tag, ChunkAccess.TicksToSave ticks) {
+        tag.put("block_ticks", ticks.blocks().save(0, (block) -> BuiltInRegistries.BLOCK.getKey(block).toString()));
+        tag.put("fluid_ticks", ticks.fluids().save(0, (fluid) -> BuiltInRegistries.FLUID.getKey(fluid).toString()));
+    }
+}

nms/v1_21_R1/src/main/java/com/volmit/iris/core/nms/v1_21_R1/NMSBinding.java

@@ -18,6 +18,8 @@ import com.mojang.serialization.Lifecycle;
 import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
 import com.volmit.iris.core.nms.datapack.DataVersion;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
+import com.volmit.iris.core.nms.v1_21_R1.headless.RegionStorage;
 import com.volmit.iris.util.scheduling.J;
 import lombok.SneakyThrows;
 import net.minecraft.core.*;
@@ -32,11 +34,16 @@ import net.minecraft.server.level.ChunkMap;
 import net.minecraft.tags.TagKey;
 import net.minecraft.world.item.component.CustomData;
 import net.minecraft.world.level.LevelReader;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.EntityBlock;
 import net.minecraft.world.level.chunk.status.ChunkStatus;
 import net.minecraft.world.level.chunk.status.WorldGenContext;
 import net.minecraft.world.level.dimension.DimensionType;
 import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.FlatLevelSource;
+import net.minecraft.world.level.levelgen.flat.FlatLayerInfo;
+import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
 import org.bukkit.*;
 import org.bukkit.block.Biome;
 import org.bukkit.block.data.BlockData;
@@ -670,6 +677,11 @@ public class NMSBinding implements INMSBinding {
         return keys;
     }
 
+    @Override
+    public IRegionStorage createRegionStorage(Engine engine) {
+        return new RegionStorage(engine);
+    }
+
     @Override
     public AutoClosing injectLevelStems() {
         return inject(this::supplier);
@@ -704,6 +716,15 @@ public class NMSBinding implements INMSBinding {
                 }));
     }
 
+    @Override
+    public boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end) {
+        var registry = registry().registryOrThrow(Registries.DIMENSION_TYPE);
+        if (overworld) overworld = !registry.containsKey(createIrisKey(LevelStem.OVERWORLD));
+        if (nether) nether = !registry.containsKey(createIrisKey(LevelStem.NETHER));
+        if (end) end = !registry.containsKey(createIrisKey(LevelStem.END));
+        return overworld || nether || end;
+    }
+
     private WorldLoader.DataLoadContext supplier(WorldLoader.DataLoadContext old) {
         return dataLoadContext.aquire(() -> new WorldLoader.DataLoadContext(
                 old.resources(),
@@ -734,23 +755,32 @@ public class NMSBinding implements INMSBinding {
     private RegistryAccess.Frozen createRegistryAccess(RegistryAccess.Frozen datapack, boolean copy, boolean overworld, boolean nether, boolean end) {
         var access = registry();
         var dimensions = access.registryOrThrow(Registries.DIMENSION_TYPE);
-        var levelStems = access.registryOrThrow(Registries.LEVEL_STEM);
 
+        var settings = new FlatLevelGeneratorSettings(
+                Optional.empty(),
+                access.lookupOrThrow(Registries.BIOME).getOrThrow(Biomes.THE_VOID),
+                List.of()
+        );
+        settings.getLayersInfo().add(new FlatLayerInfo(1, Blocks.AIR));
+        settings.updateLayers();
+
+        var source = new FlatLevelSource(settings);
         var fake = new MappedRegistry<>(Registries.LEVEL_STEM, Lifecycle.experimental());
-        if (overworld) register(fake, levelStems, dimensions, LevelStem.OVERWORLD);
+        if (overworld) register(fake, dimensions, source, LevelStem.OVERWORLD);
-        if (nether) register(fake, levelStems, dimensions, LevelStem.NETHER);
+        if (nether) register(fake, dimensions, source, LevelStem.NETHER);
-        if (end) register(fake, levelStems, dimensions, LevelStem.END);
+        if (end) register(fake, dimensions, source, LevelStem.END);
         copy(fake, datapack.registry(Registries.LEVEL_STEM).orElse(null));
 
-        if (copy) copy(fake, levelStems);
+        if (copy) copy(fake, access.registryOrThrow(Registries.LEVEL_STEM));
 
         return new RegistryAccess.Frozen.ImmutableRegistryAccess(List.of(fake.freeze())).freeze();
     }
 
-    private void register(MappedRegistry<LevelStem> target, Registry<LevelStem> levelStems, Registry<DimensionType> dimensions, ResourceKey<LevelStem> key) {
+    private void register(MappedRegistry<LevelStem> target, Registry<DimensionType> dimensions, FlatLevelSource source, ResourceKey<LevelStem> key) {
+        var loc = createIrisKey(key);
         target.register(key, new LevelStem(
-                dimensions.getHolder(ResourceLocation.fromNamespaceAndPath("iris", key.location().getPath())).orElseThrow(),
+                dimensions.getHolder(ResourceKey.create(Registries.DIMENSION_TYPE, loc)).orElseThrow(() -> new IllegalStateException("Missing dimension type " + loc + " in " + dimensions.keySet())),
-                levelStems.getOrThrow(key).generator()
+                source
         ), RegistrationInfo.BUILT_IN);
     }
 
@@ -763,4 +793,8 @@ public class NMSBinding implements INMSBinding {
                 target.register(key, value, info);
         });
     }
+
+    private ResourceLocation createIrisKey(ResourceKey<LevelStem> key) {
+        return ResourceLocation.fromNamespaceAndPath("iris", key.location().getPath());
+    }
 }

nms/v1_21_R1/src/main/java/com/volmit/iris/core/nms/v1_21_R1/headless/DirectTerrainChunk.java

@@ -0,0 +1,211 @@
+package com.volmit.iris.core.nms.v1_21_R1.headless;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.BiomeBaseInjector;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.util.data.IrisCustomData;
+import com.volmit.iris.util.math.Position2;
+import lombok.Data;
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.EntityBlock;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import org.bukkit.Material;
+import org.bukkit.block.Biome;
+import org.bukkit.block.data.BlockData;
+import org.bukkit.craftbukkit.v1_21_R1.block.CraftBiome;
+import org.bukkit.craftbukkit.v1_21_R1.block.CraftBlockType;
+import org.bukkit.craftbukkit.v1_21_R1.block.data.CraftBlockData;
+import org.bukkit.craftbukkit.v1_21_R1.util.CraftMagicNumbers;
+import org.bukkit.generator.ChunkGenerator;
+import org.bukkit.material.MaterialData;
+import org.jetbrains.annotations.NotNull;
+
+@Data
+public final class DirectTerrainChunk implements SerializableChunk {
+    private final ProtoChunk access;
+    private final int minHeight, maxHeight;
+
+    public DirectTerrainChunk(ProtoChunk access) {
+        this.access = access;
+        this.minHeight = access.getMinBuildHeight();
+        this.maxHeight = access.getMaxBuildHeight();
+    }
+
+    @Override
+    public BiomeBaseInjector getBiomeBaseInjector() {
+        return null;
+    }
+
+    @NotNull
+    @Override
+    public Biome getBiome(int x, int z) {
+        return getBiome(x, 0, z);
+    }
+
+    @NotNull
+    @Override
+    public Biome getBiome(int x, int y, int z) {
+        if (y < minHeight || y > maxHeight) return Biome.PLAINS;
+        return CraftBiome.minecraftHolderToBukkit(access.getNoiseBiome(x >> 2, y >> 2, z >> 2));
+    }
+
+    @Override
+    public void setBiome(int x, int z, Biome bio) {
+        for (int y = minHeight; y < maxHeight; y += 4) {
+            setBiome(x, y, z, bio);
+        }
+    }
+
+    @Override
+    public void setBiome(int x, int y, int z, Biome bio) {
+        if (y < minHeight || y > maxHeight) return;
+        access.setBiome(x & 15, y, z & 15, CraftBiome.bukkitToMinecraftHolder(bio));
+    }
+
+    public void setBlock(int x, int y, int z, Material material) {
+        this.setBlock(x, y, z, material.createBlockData());
+    }
+
+    public void setBlock(int x, int y, int z, MaterialData material) {
+        this.setBlock(x, y, z, CraftMagicNumbers.getBlock(material));
+    }
+
+    @Override
+    public void setBlock(int x, int y, int z, BlockData blockData) {
+        if (blockData == null) {
+            Iris.error("NULL BD");
+        }
+        if (blockData instanceof IrisCustomData data)
+            blockData = data.getBase();
+        if (!(blockData instanceof CraftBlockData craftBlockData))
+            throw new IllegalArgumentException("Expected CraftBlockData, got " + blockData.getClass().getSimpleName() + " instead");
+        access.setBlockState(new BlockPos(x & 15, y, z & 15), craftBlockData.getState(), false);
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, Material material) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, material.createBlockData());
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, MaterialData material) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, CraftMagicNumbers.getBlock(material));
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, BlockData blockData) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, ((CraftBlockData) blockData).getState());
+    }
+
+    public Material getType(int x, int y, int z) {
+        return CraftBlockType.minecraftToBukkit(this.getTypeId(x, y, z).getBlock());
+    }
+
+    public MaterialData getTypeAndData(int x, int y, int z) {
+        return CraftMagicNumbers.getMaterial(this.getTypeId(x, y, z));
+    }
+
+    public BlockData getBlockData(int x, int y, int z) {
+        return CraftBlockData.fromData(this.getTypeId(x, y, z));
+    }
+
+    @Override
+    public ChunkGenerator.ChunkData getRaw() {
+        return null;
+    }
+
+    @Override
+    public void setRaw(ChunkGenerator.ChunkData data) {
+
+    }
+
+    @Override
+    public void inject(ChunkGenerator.BiomeGrid biome) {
+
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, BlockState type) {
+        if (xMin > 15 || yMin >= this.maxHeight || zMin > 15)
+            return;
+
+        if (xMin < 0) {
+            xMin = 0;
+        }
+
+        if (yMin < this.minHeight) {
+            yMin = this.minHeight;
+        }
+
+        if (zMin < 0) {
+            zMin = 0;
+        }
+
+        if (xMax > 16) {
+            xMax = 16;
+        }
+
+        if (yMax > this.maxHeight) {
+            yMax = this.maxHeight;
+        }
+
+        if (zMax > 16) {
+            zMax = 16;
+        }
+
+        if (xMin >= xMax || yMin >= yMax || zMin >= zMax)
+            return;
+
+        for (int y = yMin; y < yMax; ++y) {
+            for (int x = xMin; x < xMax; ++x) {
+                for (int z = zMin; z < zMax; ++z) {
+                    this.setBlock(x, y, z, type);
+                }
+            }
+        }
+
+    }
+
+    public BlockState getTypeId(int x, int y, int z) {
+        if (x != (x & 15) || y < this.minHeight || y >= this.maxHeight || z != (z & 15))
+            return Blocks.AIR.defaultBlockState();
+        return access.getBlockState(new BlockPos(access.getPos().getMinBlockX() + x, y, access.getPos().getMinBlockZ() + z));
+    }
+
+    public byte getData(int x, int y, int z) {
+        return CraftMagicNumbers.toLegacyData(this.getTypeId(x, y, z));
+    }
+
+    private void setBlock(int x, int y, int z, BlockState type) {
+        if (x != (x & 15) || y < this.minHeight || y >= this.maxHeight || z != (z & 15))
+            return;
+        BlockPos blockPosition = new BlockPos(access.getPos().getMinBlockX() + x, y, access.getPos().getMinBlockZ() + z);
+        BlockState oldBlockData = access.setBlockState(blockPosition, type, false);
+        if (type.hasBlockEntity()) {
+            BlockEntity tileEntity = ((EntityBlock) type.getBlock()).newBlockEntity(blockPosition, type);
+            if (tileEntity == null) {
+                access.removeBlockEntity(blockPosition);
+            } else {
+                access.setBlockEntity(tileEntity);
+            }
+        } else if (oldBlockData != null && oldBlockData.hasBlockEntity()) {
+            access.removeBlockEntity(blockPosition);
+        }
+
+    }
+
+    @Override
+    public Position2 getPos() {
+        return new Position2(access.getPos().x, access.getPos().z);
+    }
+
+    @Override
+    public Object serialize() {
+        return RegionStorage.serialize(access);
+    }
+
+    @Override
+    public void mark() {
+        access.setPersistedStatus(ChunkStatus.FULL);
+    }
+}

nms/v1_21_R1/src/main/java/com/volmit/iris/core/nms/v1_21_R1/headless/Region.java

@@ -0,0 +1,75 @@
+package com.volmit.iris.core.nms.v1_21_R1.headless;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.headless.IRegion;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.util.math.M;
+import lombok.NonNull;
+import lombok.Synchronized;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.NbtIo;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.chunk.storage.RegionFile;
+import net.minecraft.world.level.chunk.storage.RegionStorageInfo;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.nio.file.Path;
+
+class Region implements IRegion, Comparable<Region> {
+    private static final RegionStorageInfo info = new RegionStorageInfo("headless", Level.OVERWORLD, "headless");
+    private final RegionFile regionFile;
+    transient long references;
+    transient long lastUsed;
+
+    Region(Path path, Path folder) throws IOException {
+        this.regionFile = new RegionFile(info, path, folder, false);
+    }
+
+    @Override
+    @Synchronized
+    public boolean exists(int x, int z) {
+        try (DataInputStream din = regionFile.getChunkDataInputStream(new ChunkPos(x, z))) {
+            if (din == null) return false;
+            return !"empty".equals(NbtIo.read(din).getString("Status"));
+        } catch (IOException e) {
+            return false;
+        }
+    }
+
+    @Override
+    @Synchronized
+    public void write(@NonNull SerializableChunk chunk) throws IOException {
+        try (DataOutputStream dos = regionFile.getChunkDataOutputStream(chunk.getPos().convert(ChunkPos::new))) {
+            NbtIo.write((CompoundTag) chunk.serialize(), dos);
+        }
+    }
+
+    @Override
+    public void close() {
+        --references;
+        lastUsed = M.ms();
+    }
+
+    public boolean unused() {
+        return references <= 0;
+    }
+
+    public boolean remove() {
+        if (!unused()) return false;
+        try {
+            regionFile.close();
+        } catch (IOException e) {
+            Iris.error("Failed to close region file");
+            e.printStackTrace();
+        }
+        return true;
+    }
+
+    @Override
+    public int compareTo(Region o) {
+        return Long.compare(lastUsed, o.lastUsed);
+    }
+}

nms/v1_21_R1/src/main/java/com/volmit/iris/core/nms/v1_21_R1/headless/RegionStorage.java

@@ -0,0 +1,307 @@
+package com.volmit.iris.core.nms.v1_21_R1.headless;
+
+import com.mojang.logging.LogUtils;
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.DataResult;
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.headless.IRegion;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.engine.data.cache.AtomicCache;
+import com.volmit.iris.engine.data.cache.Cache;
+import com.volmit.iris.engine.framework.Engine;
+import com.volmit.iris.engine.object.IrisBiome;
+import com.volmit.iris.util.collection.KMap;
+import com.volmit.iris.util.context.ChunkContext;
+import com.volmit.iris.util.math.RNG;
+import com.volmit.iris.util.scheduling.J;
+import lombok.Getter;
+import lombok.NonNull;
+import net.minecraft.FileUtil;
+import net.minecraft.core.*;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.nbt.*;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.chunk.*;
+import net.minecraft.world.level.chunk.status.ChunkType;
+import net.minecraft.world.level.levelgen.BelowZeroRetrogen;
+import net.minecraft.world.level.levelgen.GenerationStep;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.blending.BlendingData;
+import org.bukkit.Bukkit;
+import org.bukkit.craftbukkit.v1_21_R1.CraftServer;
+import org.bukkit.craftbukkit.v1_21_R1.block.CraftBiome;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.*;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+import static net.minecraft.world.level.chunk.storage.ChunkSerializer.BLOCK_STATE_CODEC;
+import static net.minecraft.world.level.chunk.storage.ChunkSerializer.packOffsets;
+
+public class RegionStorage implements IRegionStorage, LevelHeightAccessor {
+    private static final AtomicCache<RegistryAccess> CACHE = new AtomicCache<>();
+    private final KMap<Long, Region> regions = new KMap<>();
+    private final Path folder;
+
+    private final Engine engine;
+    private final KMap<String, Holder<Biome>> customBiomes = new KMap<>();
+    private final KMap<org.bukkit.block.Biome, Holder<Biome>> minecraftBiomes;
+    private final RNG biomeRng;
+    private final @Getter int minBuildHeight;
+    private final @Getter int height;
+
+    private transient boolean closed = false;
+
+    public RegionStorage(Engine engine) {
+        this.engine = engine;
+        this.folder = new File(engine.getWorld().worldFolder(), "region").toPath();
+        this.biomeRng = new RNG(engine.getSeedManager().getBiome());
+
+        this.minBuildHeight = engine.getDimension().getMinHeight();
+        this.height = engine.getDimension().getMaxHeight() - minBuildHeight;
+
+        AtomicInteger failed = new AtomicInteger();
+        var dimKey = engine.getDimension().getLoadKey();
+        for (var biome : engine.getAllBiomes()) {
+            if (!biome.isCustom()) continue;
+            for (var custom : biome.getCustomDerivitives()) {
+                biomeHolder(dimKey, custom.getId()).ifPresentOrElse(holder -> customBiomes.put(custom.getId(), holder), () -> {
+                    Iris.error("Failed to load custom biome " + dimKey + " " + custom.getId());
+                    failed.incrementAndGet();
+                });
+            }
+        }
+        if (failed.get() > 0) {
+            throw new IllegalStateException("Failed to load " + failed.get() + " custom biomes");
+        }
+
+        minecraftBiomes = new KMap<>(org.bukkit.Registry.BIOME.stream()
+                .filter(biome -> biome != org.bukkit.block.Biome.CUSTOM)
+                .collect(Collectors.toMap(Function.identity(), CraftBiome::bukkitToMinecraftHolder)));
+        minecraftBiomes.values().removeAll(customBiomes.values());
+    }
+
+    @Override
+    public boolean exists(int x, int z) {
+        try (IRegion region = getRegion(x >> 5, z >> 5, true)) {
+            return region != null && region.exists(x, z);
+        } catch (Exception e) {
+            return false;
+        }
+    }
+
+    @Override
+    public IRegion getRegion(int x, int z, boolean existingOnly) throws IOException {
+        AtomicReference<IOException> exception = new AtomicReference<>();
+        Region region = regions.computeIfAbsent(Cache.key(x, z), k -> {
+            trim();
+
+            try {
+                FileUtil.createDirectoriesSafe(this.folder);
+                Path path = folder.resolve("r." + x + "." + z + ".mca");
+                if (existingOnly && !Files.exists(path)) {
+                    return null;
+                } else {
+                    return new Region(path, this.folder);
+                }
+            } catch (IOException e) {
+                exception.set(e);
+                return null;
+            }
+        });
+
+        if (region == null) {
+            if (exception.get() != null)
+                throw exception.get();
+            return null;
+        }
+        region.references++;
+        return region;
+    }
+
+    @NotNull
+    @Override
+    public SerializableChunk createChunk(int x, int z) {
+        return new DirectTerrainChunk(new ProtoChunk(new ChunkPos(x, z), UpgradeData.EMPTY, this, registryAccess().registryOrThrow(Registries.BIOME), null));
+    }
+
+    @Override
+    public void fillBiomes(@NonNull SerializableChunk chunk, @Nullable ChunkContext ctx) {
+        if (!(chunk instanceof DirectTerrainChunk tc))
+            return;
+        tc.getAccess().fillBiomesFromNoise((qX, qY, qZ, sampler) -> getNoiseBiome(engine, ctx, qX << 2, qY << 2, qZ << 2), null);
+    }
+
+    @Override
+    public synchronized void close() {
+        if (closed) return;
+
+        while (!regions.isEmpty()) {
+            regions.values().removeIf(Region::remove);
+            J.sleep(1);
+        }
+
+        closed = true;
+        customBiomes.clear();
+        minecraftBiomes.clear();
+    }
+
+    private void trim() {
+        int size = regions.size();
+        if (size < 256) return;
+        int remove = size - 255;
+
+        var list = regions.values()
+                .stream()
+                .filter(Region::unused)
+                .sorted()
+                .collect(Collectors.toList())
+                .reversed();
+
+        int skip = list.size() - remove;
+        if (skip > 0) list.subList(0, skip).clear();
+
+        if (list.isEmpty()) return;
+        regions.values().removeIf(r -> list.contains(r) && r.remove());
+    }
+
+    private Holder<Biome> getNoiseBiome(Engine engine, ChunkContext ctx, int x, int y, int z) {
+        int m = y - engine.getMinHeight();
+        IrisBiome ib = ctx == null ? engine.getSurfaceBiome(x, z) : ctx.getBiome().get(x & 15, z & 15);
+        if (ib.isCustom()) {
+            return customBiomes.get(ib.getCustomBiome(biomeRng, x, m, z).getId());
+        } else {
+            return minecraftBiomes.get(ib.getSkyBiome(biomeRng, x, m, z));
+        }
+    }
+
+    private static RegistryAccess registryAccess() {
+        return CACHE.aquire(() -> ((CraftServer) Bukkit.getServer()).getServer().registryAccess());
+    }
+
+    private static Optional<Holder.Reference<Biome>> biomeHolder(String namespace, String path) {
+        return registryAccess().registryOrThrow(Registries.BIOME).getHolder(ResourceLocation.fromNamespaceAndPath(namespace, path));
+    }
+
+    static CompoundTag serialize(ChunkAccess chunk) {
+        ChunkPos chunkPos = chunk.getPos();
+        CompoundTag tag = NbtUtils.addCurrentDataVersion(new CompoundTag());
+        tag.putInt("xPos", chunkPos.x);
+        tag.putInt("yPos", chunk.getMinSection());
+        tag.putInt("zPos", chunkPos.z);
+        tag.putLong("LastUpdate", 0);
+        tag.putLong("InhabitedTime", chunk.getInhabitedTime());
+        tag.putString("Status", BuiltInRegistries.CHUNK_STATUS.getKey(chunk.getPersistedStatus()).toString());
+        BlendingData blendingdata = chunk.getBlendingData();
+        if (blendingdata != null) {
+            DataResult<Tag> dataresult = BlendingData.CODEC.encodeStart(NbtOps.INSTANCE, blendingdata);
+            dataresult.resultOrPartial(LogUtils.getLogger()::error).ifPresent((nbt) -> tag.put("blending_data", nbt));
+        }
+
+        BelowZeroRetrogen retrogen = chunk.getBelowZeroRetrogen();
+        if (retrogen != null) {
+            DataResult<Tag> dataresult = BelowZeroRetrogen.CODEC.encodeStart(NbtOps.INSTANCE, retrogen);
+            dataresult.resultOrPartial(LogUtils.getLogger()::error).ifPresent((nbt) -> tag.put("below_zero_retrogen", nbt));
+        }
+
+        UpgradeData upgradeData = chunk.getUpgradeData();
+        if (!upgradeData.isEmpty()) {
+            tag.put("UpgradeData", upgradeData.write());
+        }
+
+        LevelChunkSection[] sections = chunk.getSections();
+        ListTag sectionsTag = new ListTag();
+        Registry<Biome> biomeRegistry = registryAccess().registryOrThrow(Registries.BIOME);
+        Codec<PalettedContainerRO<Holder<Biome>>> codec = PalettedContainer.codecRO(biomeRegistry.asHolderIdMap(), biomeRegistry.holderByNameCodec(), PalettedContainer.Strategy.SECTION_BIOMES, biomeRegistry.getHolderOrThrow(Biomes.PLAINS));
+        boolean flag = chunk.isLightCorrect();
+
+        int minLightSection = chunk.getMinSection() - 1;
+        int maxLightSection = minLightSection + chunk.getSectionsCount() + 2;
+        for(int y = minLightSection; y < maxLightSection; ++y) {
+            int j = chunk.getSectionIndexFromSectionY(y);
+            if (j < 0 || j >= sections.length)
+                continue;
+            CompoundTag sectionTag = new CompoundTag();
+            LevelChunkSection section = sections[j];
+            sectionTag.put("block_states", BLOCK_STATE_CODEC.encodeStart(NbtOps.INSTANCE, section.getStates()).getOrThrow());
+            sectionTag.put("biomes", codec.encodeStart(NbtOps.INSTANCE, section.getBiomes()).getOrThrow());
+
+            if (!sectionTag.isEmpty()) {
+                sectionTag.putByte("Y", (byte) y);
+                sectionsTag.add(sectionTag);
+            }
+        }
+
+        tag.put("sections", sectionsTag);
+        if (flag) {
+            tag.putBoolean("isLightOn", true);
+        }
+
+        ListTag blockEntities = new ListTag();
+        for(BlockPos blockPos : chunk.getBlockEntitiesPos()) {
+            CompoundTag entityNbt = chunk.getBlockEntityNbtForSaving(blockPos, registryAccess());
+            if (entityNbt != null) {
+                blockEntities.add(entityNbt);
+            }
+        }
+
+        tag.put("block_entities", blockEntities);
+        if (chunk.getPersistedStatus().getChunkType() == ChunkType.PROTOCHUNK) {
+            ProtoChunk protochunk = (ProtoChunk)chunk;
+            ListTag entities = new ListTag();
+            entities.addAll(protochunk.getEntities());
+            tag.put("entities", entities);
+            CompoundTag carvingMasks = new CompoundTag();
+
+            for(GenerationStep.Carving carving : GenerationStep.Carving.values()) {
+                CarvingMask mask = protochunk.getCarvingMask(carving);
+                if (mask != null) {
+                    carvingMasks.putLongArray(carving.toString(), mask.toArray());
+                }
+            }
+
+            tag.put("CarvingMasks", carvingMasks);
+        }
+
+        saveTicks(tag, chunk.getTicksForSerialization());
+        tag.put("PostProcessing", packOffsets(chunk.getPostProcessing()));
+        CompoundTag heightMaps = new CompoundTag();
+
+        for(Map.Entry<Heightmap.Types, Heightmap> entry : chunk.getHeightmaps()) {
+            if (chunk.getPersistedStatus().heightmapsAfter().contains(entry.getKey())) {
+                heightMaps.put(entry.getKey().getSerializationKey(), new LongArrayTag(entry.getValue().getRawData()));
+            }
+        }
+
+        tag.put("Heightmaps", heightMaps);
+
+        CompoundTag structureData = new CompoundTag();
+        structureData.put("starts", new CompoundTag());
+        structureData.put("References", new CompoundTag());
+        tag.put("structures", structureData);
+        if (!chunk.persistentDataContainer.isEmpty()) {
+            tag.put("ChunkBukkitValues", chunk.persistentDataContainer.toTagCompound());
+        }
+
+        return tag;
+    }
+
+    private static void saveTicks(CompoundTag tag, ChunkAccess.TicksToSave ticks) {
+        tag.put("block_ticks", ticks.blocks().save(0, (block) -> BuiltInRegistries.BLOCK.getKey(block).toString()));
+        tag.put("fluid_ticks", ticks.fluids().save(0, (fluid) -> BuiltInRegistries.FLUID.getKey(fluid).toString()));
+    }
+}

nms/v1_21_R2/src/main/java/com/volmit/iris/core/nms/v1_21_R2/NMSBinding.java

@@ -14,6 +14,8 @@ import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
 import com.volmit.iris.core.nms.container.Pair;
 import com.volmit.iris.core.nms.datapack.DataVersion;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
+import com.volmit.iris.core.nms.v1_21_R2.headless.RegionStorage;
 import com.volmit.iris.util.scheduling.J;
 import lombok.SneakyThrows;
 import net.minecraft.core.*;
@@ -27,11 +29,16 @@ import net.minecraft.server.commands.data.BlockDataAccessor;
 import net.minecraft.tags.TagKey;
 import net.minecraft.world.item.component.CustomData;
 import net.minecraft.world.level.LevelReader;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.EntityBlock;
 import net.minecraft.world.level.chunk.status.ChunkStatus;
 import net.minecraft.world.level.chunk.status.WorldGenContext;
 import net.minecraft.world.level.dimension.DimensionType;
 import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.FlatLevelSource;
+import net.minecraft.world.level.levelgen.flat.FlatLayerInfo;
+import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
 import org.bukkit.*;
 import org.bukkit.block.Biome;
 import org.bukkit.block.data.BlockData;
@@ -660,6 +667,11 @@ public class NMSBinding implements INMSBinding {
         return keys;
     }
 
+    @Override
+    public IRegionStorage createRegionStorage(Engine engine) {
+        return new RegionStorage(engine);
+    }
+
     @Override
     public AutoClosing injectLevelStems() {
         return inject(this::supplier);
@@ -694,6 +706,15 @@ public class NMSBinding implements INMSBinding {
                 }));
     }
 
+    @Override
+    public boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end) {
+        var registry = registry().lookupOrThrow(Registries.DIMENSION_TYPE);
+        if (overworld) overworld = !registry.containsKey(createIrisKey(LevelStem.OVERWORLD));
+        if (nether) nether = !registry.containsKey(createIrisKey(LevelStem.NETHER));
+        if (end) end = !registry.containsKey(createIrisKey(LevelStem.END));
+        return overworld || nether || end;
+    }
+
     private WorldLoader.DataLoadContext supplier(WorldLoader.DataLoadContext old) {
         return dataLoadContext.aquire(() -> new WorldLoader.DataLoadContext(
                 old.resources(),
@@ -724,23 +745,32 @@ public class NMSBinding implements INMSBinding {
     private RegistryAccess.Frozen createRegistryAccess(RegistryAccess.Frozen datapack, boolean copy, boolean overworld, boolean nether, boolean end) {
         var access = registry();
         var dimensions = access.lookupOrThrow(Registries.DIMENSION_TYPE);
-        var levelStems = access.lookupOrThrow(Registries.LEVEL_STEM);
 
+        var settings = new FlatLevelGeneratorSettings(
+                Optional.empty(),
+                access.lookupOrThrow(Registries.BIOME).getOrThrow(Biomes.THE_VOID),
+                List.of()
+        );
+        settings.getLayersInfo().add(new FlatLayerInfo(1, Blocks.AIR));
+        settings.updateLayers();
+
+        var source = new FlatLevelSource(settings);
         var fake = new MappedRegistry<>(Registries.LEVEL_STEM, Lifecycle.experimental());
-        if (overworld) register(fake, levelStems, dimensions, LevelStem.OVERWORLD);
+        if (overworld) register(fake, dimensions, source, LevelStem.OVERWORLD);
-        if (nether) register(fake, levelStems, dimensions, LevelStem.NETHER);
+        if (nether) register(fake, dimensions, source, LevelStem.NETHER);
-        if (end) register(fake, levelStems, dimensions, LevelStem.END);
+        if (end) register(fake, dimensions, source, LevelStem.END);
         copy(fake, datapack.lookup(Registries.LEVEL_STEM).orElse(null));
 
-        if (copy) copy(fake, levelStems);
+        if (copy) copy(fake, access.lookupOrThrow(Registries.LEVEL_STEM));
 
         return new RegistryAccess.Frozen.ImmutableRegistryAccess(List.of(fake.freeze())).freeze();
     }
 
-    private void register(MappedRegistry<LevelStem> target, Registry<LevelStem> levelStems, Registry<DimensionType> dimensions, ResourceKey<LevelStem> key) {
+    private void register(MappedRegistry<LevelStem> target, Registry<DimensionType> dimensions, FlatLevelSource source, ResourceKey<LevelStem> key) {
+        var loc = createIrisKey(key);
         target.register(key, new LevelStem(
-                dimensions.get(ResourceLocation.fromNamespaceAndPath("iris", key.location().getPath())).orElseThrow(),
+                dimensions.get(loc).orElseThrow(() -> new IllegalStateException("Missing dimension type " + loc + " in " + dimensions.keySet())),
-                levelStems.getValueOrThrow(key).generator()
+                source
         ), RegistrationInfo.BUILT_IN);
     }
 
@@ -753,4 +783,8 @@ public class NMSBinding implements INMSBinding {
                 target.register(key, value, info);
         });
     }
+
+    private ResourceLocation createIrisKey(ResourceKey<LevelStem> key) {
+        return ResourceLocation.fromNamespaceAndPath("iris", key.location().getPath());
+    }
 }

nms/v1_21_R2/src/main/java/com/volmit/iris/core/nms/v1_21_R2/headless/DirectTerrainChunk.java

@@ -0,0 +1,211 @@
+package com.volmit.iris.core.nms.v1_21_R2.headless;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.BiomeBaseInjector;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.util.data.IrisCustomData;
+import com.volmit.iris.util.math.Position2;
+import lombok.Data;
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.EntityBlock;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import org.bukkit.Material;
+import org.bukkit.block.Biome;
+import org.bukkit.block.data.BlockData;
+import org.bukkit.craftbukkit.v1_21_R2.block.CraftBiome;
+import org.bukkit.craftbukkit.v1_21_R2.block.CraftBlockType;
+import org.bukkit.craftbukkit.v1_21_R2.block.data.CraftBlockData;
+import org.bukkit.craftbukkit.v1_21_R2.util.CraftMagicNumbers;
+import org.bukkit.generator.ChunkGenerator;
+import org.bukkit.material.MaterialData;
+import org.jetbrains.annotations.NotNull;
+
+@Data
+public final class DirectTerrainChunk implements SerializableChunk {
+    private final ProtoChunk access;
+    private final int minHeight, maxHeight;
+
+    public DirectTerrainChunk(ProtoChunk access) {
+        this.access = access;
+        this.minHeight = access.getMinY();
+        this.maxHeight = access.getMaxY();
+    }
+
+    @Override
+    public BiomeBaseInjector getBiomeBaseInjector() {
+        return null;
+    }
+
+    @NotNull
+    @Override
+    public Biome getBiome(int x, int z) {
+        return getBiome(x, 0, z);
+    }
+
+    @NotNull
+    @Override
+    public Biome getBiome(int x, int y, int z) {
+        if (y < minHeight || y > maxHeight) return Biome.PLAINS;
+        return CraftBiome.minecraftHolderToBukkit(access.getNoiseBiome(x >> 2, y >> 2, z >> 2));
+    }
+
+    @Override
+    public void setBiome(int x, int z, Biome bio) {
+        for (int y = minHeight; y < maxHeight; y += 4) {
+            setBiome(x, y, z, bio);
+        }
+    }
+
+    @Override
+    public void setBiome(int x, int y, int z, Biome bio) {
+        if (y < minHeight || y > maxHeight) return;
+        access.setBiome(x & 15, y, z & 15, CraftBiome.bukkitToMinecraftHolder(bio));
+    }
+
+    public void setBlock(int x, int y, int z, Material material) {
+        this.setBlock(x, y, z, material.createBlockData());
+    }
+
+    public void setBlock(int x, int y, int z, MaterialData material) {
+        this.setBlock(x, y, z, CraftMagicNumbers.getBlock(material));
+    }
+
+    @Override
+    public void setBlock(int x, int y, int z, BlockData blockData) {
+        if (blockData == null) {
+            Iris.error("NULL BD");
+        }
+        if (blockData instanceof IrisCustomData data)
+            blockData = data.getBase();
+        if (!(blockData instanceof CraftBlockData craftBlockData))
+            throw new IllegalArgumentException("Expected CraftBlockData, got " + blockData.getClass().getSimpleName() + " instead");
+        access.setBlockState(new BlockPos(x & 15, y, z & 15), craftBlockData.getState(), false);
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, Material material) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, material.createBlockData());
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, MaterialData material) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, CraftMagicNumbers.getBlock(material));
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, BlockData blockData) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, ((CraftBlockData) blockData).getState());
+    }
+
+    public Material getType(int x, int y, int z) {
+        return CraftBlockType.minecraftToBukkit(this.getTypeId(x, y, z).getBlock());
+    }
+
+    public MaterialData getTypeAndData(int x, int y, int z) {
+        return CraftMagicNumbers.getMaterial(this.getTypeId(x, y, z));
+    }
+
+    public BlockData getBlockData(int x, int y, int z) {
+        return CraftBlockData.fromData(this.getTypeId(x, y, z));
+    }
+
+    @Override
+    public ChunkGenerator.ChunkData getRaw() {
+        return null;
+    }
+
+    @Override
+    public void setRaw(ChunkGenerator.ChunkData data) {
+
+    }
+
+    @Override
+    public void inject(ChunkGenerator.BiomeGrid biome) {
+
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, BlockState type) {
+        if (xMin > 15 || yMin >= this.maxHeight || zMin > 15)
+            return;
+
+        if (xMin < 0) {
+            xMin = 0;
+        }
+
+        if (yMin < this.minHeight) {
+            yMin = this.minHeight;
+        }
+
+        if (zMin < 0) {
+            zMin = 0;
+        }
+
+        if (xMax > 16) {
+            xMax = 16;
+        }
+
+        if (yMax > this.maxHeight) {
+            yMax = this.maxHeight;
+        }
+
+        if (zMax > 16) {
+            zMax = 16;
+        }
+
+        if (xMin >= xMax || yMin >= yMax || zMin >= zMax)
+            return;
+
+        for (int y = yMin; y < yMax; ++y) {
+            for (int x = xMin; x < xMax; ++x) {
+                for (int z = zMin; z < zMax; ++z) {
+                    this.setBlock(x, y, z, type);
+                }
+            }
+        }
+
+    }
+
+    public BlockState getTypeId(int x, int y, int z) {
+        if (x != (x & 15) || y < this.minHeight || y >= this.maxHeight || z != (z & 15))
+            return Blocks.AIR.defaultBlockState();
+        return access.getBlockState(new BlockPos(access.getPos().getMinBlockX() + x, y, access.getPos().getMinBlockZ() + z));
+    }
+
+    public byte getData(int x, int y, int z) {
+        return CraftMagicNumbers.toLegacyData(this.getTypeId(x, y, z));
+    }
+
+    private void setBlock(int x, int y, int z, BlockState type) {
+        if (x != (x & 15) || y < this.minHeight || y >= this.maxHeight || z != (z & 15))
+            return;
+        BlockPos blockPosition = new BlockPos(access.getPos().getMinBlockX() + x, y, access.getPos().getMinBlockZ() + z);
+        BlockState oldBlockData = access.setBlockState(blockPosition, type, false);
+        if (type.hasBlockEntity()) {
+            BlockEntity tileEntity = ((EntityBlock) type.getBlock()).newBlockEntity(blockPosition, type);
+            if (tileEntity == null) {
+                access.removeBlockEntity(blockPosition);
+            } else {
+                access.setBlockEntity(tileEntity);
+            }
+        } else if (oldBlockData != null && oldBlockData.hasBlockEntity()) {
+            access.removeBlockEntity(blockPosition);
+        }
+
+    }
+
+    @Override
+    public Position2 getPos() {
+        return new Position2(access.getPos().x, access.getPos().z);
+    }
+
+    @Override
+    public Object serialize() {
+        return RegionStorage.serialize(access);
+    }
+
+    @Override
+    public void mark() {
+        access.setPersistedStatus(ChunkStatus.FULL);
+    }
+}

nms/v1_21_R2/src/main/java/com/volmit/iris/core/nms/v1_21_R2/headless/Region.java

@@ -0,0 +1,75 @@
+package com.volmit.iris.core.nms.v1_21_R2.headless;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.headless.IRegion;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.util.math.M;
+import lombok.NonNull;
+import lombok.Synchronized;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.NbtIo;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.chunk.storage.RegionFile;
+import net.minecraft.world.level.chunk.storage.RegionStorageInfo;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.nio.file.Path;
+
+class Region implements IRegion, Comparable<Region> {
+    private static final RegionStorageInfo info = new RegionStorageInfo("headless", Level.OVERWORLD, "headless");
+    private final RegionFile regionFile;
+    transient long references;
+    transient long lastUsed;
+
+    Region(Path path, Path folder) throws IOException {
+        this.regionFile = new RegionFile(info, path, folder, false);
+    }
+
+    @Override
+    @Synchronized
+    public boolean exists(int x, int z) {
+        try (DataInputStream din = regionFile.getChunkDataInputStream(new ChunkPos(x, z))) {
+            if (din == null) return false;
+            return !"empty".equals(NbtIo.read(din).getString("Status"));
+        } catch (IOException e) {
+            return false;
+        }
+    }
+
+    @Override
+    @Synchronized
+    public void write(@NonNull SerializableChunk chunk) throws IOException {
+        try (DataOutputStream dos = regionFile.getChunkDataOutputStream(chunk.getPos().convert(ChunkPos::new))) {
+            NbtIo.write((CompoundTag) chunk.serialize(), dos);
+        }
+    }
+
+    @Override
+    public void close() {
+        --references;
+        lastUsed = M.ms();
+    }
+
+    public boolean unused() {
+        return references <= 0;
+    }
+
+    public boolean remove() {
+        if (!unused()) return false;
+        try {
+            regionFile.close();
+        } catch (IOException e) {
+            Iris.error("Failed to close region file");
+            e.printStackTrace();
+        }
+        return true;
+    }
+
+    @Override
+    public int compareTo(Region o) {
+        return Long.compare(lastUsed, o.lastUsed);
+    }
+}

nms/v1_21_R2/src/main/java/com/volmit/iris/core/nms/v1_21_R2/headless/RegionStorage.java

@@ -0,0 +1,244 @@
+package com.volmit.iris.core.nms.v1_21_R2.headless;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.headless.IRegion;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.engine.data.cache.AtomicCache;
+import com.volmit.iris.engine.data.cache.Cache;
+import com.volmit.iris.engine.framework.Engine;
+import com.volmit.iris.engine.object.IrisBiome;
+import com.volmit.iris.util.collection.KMap;
+import com.volmit.iris.util.context.ChunkContext;
+import com.volmit.iris.util.math.RNG;
+import com.volmit.iris.util.scheduling.J;
+import it.unimi.dsi.fastutil.shorts.ShortArrayList;
+import it.unimi.dsi.fastutil.shorts.ShortList;
+import lombok.Getter;
+import lombok.NonNull;
+import net.minecraft.FileUtil;
+import net.minecraft.Optionull;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.UpgradeData;
+import net.minecraft.world.level.chunk.storage.SerializableChunkData;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.blending.BlendingData;
+import org.bukkit.Bukkit;
+import org.bukkit.craftbukkit.v1_21_R2.CraftServer;
+import org.bukkit.craftbukkit.v1_21_R2.block.CraftBiome;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.*;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+public class RegionStorage implements IRegionStorage, LevelHeightAccessor {
+    private static final AtomicCache<RegistryAccess> CACHE = new AtomicCache<>();
+    private final KMap<Long, Region> regions = new KMap<>();
+    private final Path folder;
+
+    private final Engine engine;
+    private final KMap<String, Holder<Biome>> customBiomes = new KMap<>();
+    private final KMap<org.bukkit.block.Biome, Holder<Biome>> minecraftBiomes;
+    private final RNG biomeRng;
+    private final @Getter int minY;
+    private final @Getter int height;
+
+    private transient boolean closed = false;
+
+    public RegionStorage(Engine engine) {
+        this.engine = engine;
+        this.folder = new File(engine.getWorld().worldFolder(), "region").toPath();
+        this.biomeRng = new RNG(engine.getSeedManager().getBiome());
+
+        this.minY = engine.getDimension().getMinHeight();
+        this.height = engine.getDimension().getMaxHeight() - minY;
+
+        AtomicInteger failed = new AtomicInteger();
+        var dimKey = engine.getDimension().getLoadKey();
+        for (var biome : engine.getAllBiomes()) {
+            if (!biome.isCustom()) continue;
+            for (var custom : biome.getCustomDerivitives()) {
+                biomeHolder(dimKey, custom.getId()).ifPresentOrElse(holder -> customBiomes.put(custom.getId(), holder), () -> {
+                    Iris.error("Failed to load custom biome " + dimKey + " " + custom.getId());
+                    failed.incrementAndGet();
+                });
+            }
+        }
+        if (failed.get() > 0) {
+            throw new IllegalStateException("Failed to load " + failed.get() + " custom biomes");
+        }
+
+        minecraftBiomes = new KMap<>(org.bukkit.Registry.BIOME.stream()
+                .collect(Collectors.toMap(Function.identity(), CraftBiome::bukkitToMinecraftHolder)));
+        minecraftBiomes.values().removeAll(customBiomes.values());
+    }
+
+    @Override
+    public boolean exists(int x, int z) {
+        try (IRegion region = getRegion(x >> 5, z >> 5, true)) {
+            return region != null && region.exists(x, z);
+        } catch (Exception e) {
+            return false;
+        }
+    }
+
+    @Override
+    public IRegion getRegion(int x, int z, boolean existingOnly) throws IOException {
+        AtomicReference<IOException> exception = new AtomicReference<>();
+        Region region = regions.computeIfAbsent(Cache.key(x, z), k -> {
+            trim();
+
+            try {
+                FileUtil.createDirectoriesSafe(this.folder);
+                Path path = folder.resolve("r." + x + "." + z + ".mca");
+                if (existingOnly && !Files.exists(path)) {
+                    return null;
+                } else {
+                    return new Region(path, this.folder);
+                }
+            } catch (IOException e) {
+                exception.set(e);
+                return null;
+            }
+        });
+
+        if (region == null) {
+            if (exception.get() != null)
+                throw exception.get();
+            return null;
+        }
+        region.references++;
+        return region;
+    }
+
+    @NotNull
+    @Override
+    public SerializableChunk createChunk(int x, int z) {
+        return new DirectTerrainChunk(new ProtoChunk(new ChunkPos(x, z), UpgradeData.EMPTY, this, registryAccess().lookupOrThrow(Registries.BIOME), null));
+    }
+
+    @Override
+    public void fillBiomes(@NonNull SerializableChunk chunk, @Nullable ChunkContext ctx) {
+        if (!(chunk instanceof DirectTerrainChunk tc))
+            return;
+        tc.getAccess().fillBiomesFromNoise((qX, qY, qZ, sampler) -> getNoiseBiome(engine, ctx, qX << 2, qY << 2, qZ << 2), null);
+    }
+
+    @Override
+    public synchronized void close() {
+        if (closed) return;
+
+        while (!regions.isEmpty()) {
+            regions.values().removeIf(Region::remove);
+            J.sleep(1);
+        }
+
+        closed = true;
+        customBiomes.clear();
+        minecraftBiomes.clear();
+    }
+
+    private void trim() {
+        int size = regions.size();
+        if (size < 256) return;
+        int remove = size - 255;
+
+        var list = regions.values()
+                .stream()
+                .filter(Region::unused)
+                .sorted()
+                .collect(Collectors.toList())
+                .reversed();
+
+        int skip = list.size() - remove;
+        if (skip > 0) list.subList(0, skip).clear();
+
+        if (list.isEmpty()) return;
+        regions.values().removeIf(r -> list.contains(r) && r.remove());
+    }
+
+    private Holder<Biome> getNoiseBiome(Engine engine, ChunkContext ctx, int x, int y, int z) {
+        int m = y - engine.getMinHeight();
+        IrisBiome ib = ctx == null ? engine.getSurfaceBiome(x, z) : ctx.getBiome().get(x & 15, z & 15);
+        if (ib.isCustom()) {
+            return customBiomes.get(ib.getCustomBiome(biomeRng, x, m, z).getId());
+        } else {
+            return minecraftBiomes.get(ib.getSkyBiome(biomeRng, x, m, z));
+        }
+    }
+
+    private static RegistryAccess registryAccess() {
+        return CACHE.aquire(() -> ((CraftServer) Bukkit.getServer()).getServer().registryAccess());
+    }
+
+    private static Optional<Holder.Reference<Biome>> biomeHolder(String namespace, String path) {
+        return registryAccess().lookupOrThrow(Registries.BIOME).get(ResourceLocation.fromNamespaceAndPath(namespace, path));
+    }
+
+    static CompoundTag serialize(ChunkAccess chunk) {
+        RegistryAccess access = registryAccess();
+        List<SerializableChunkData.SectionData> list = new ArrayList<>();
+        LevelChunkSection[] sections = chunk.getSections();
+
+        int minLightSection = chunk.getMinSectionY() - 1;
+        int maxLightSection = minLightSection + chunk.getSectionsCount() + 2;
+        for(int y = minLightSection; y < maxLightSection; ++y) {
+            int index = chunk.getSectionIndexFromSectionY(y);
+            if (index < 0 || index >= sections.length) continue;
+            LevelChunkSection section = sections[index].copy();
+            list.add(new SerializableChunkData.SectionData(y, section, null, null));
+        }
+
+        List<CompoundTag> blockEntities = new ArrayList<>(chunk.getBlockEntitiesPos().size());
+
+        for(BlockPos blockPos : chunk.getBlockEntitiesPos()) {
+            CompoundTag nbt = chunk.getBlockEntityNbtForSaving(blockPos, access);
+            if (nbt != null) {
+                blockEntities.add(nbt);
+            }
+        }
+        Map<Heightmap.Types, long[]> heightMap = new EnumMap<>(Heightmap.Types.class);
+        for(Map.Entry<Heightmap.Types, Heightmap> entry : chunk.getHeightmaps()) {
+            if (chunk.getPersistedStatus().heightmapsAfter().contains(entry.getKey())) {
+                heightMap.put(entry.getKey(), entry.getValue().getRawData().clone());
+            }
+        }
+
+        ChunkAccess.PackedTicks packedTicks = chunk.getTicksForSerialization(0);
+        ShortList[] postProcessing = Arrays.stream(chunk.getPostProcessing()).map((shortlist) -> shortlist != null ? new ShortArrayList(shortlist) : null).toArray(ShortList[]::new);
+        CompoundTag structureData = new CompoundTag();
+        structureData.put("starts", new CompoundTag());
+        structureData.put("References", new CompoundTag());
+
+        CompoundTag persistentDataContainer = null;
+        if (!chunk.persistentDataContainer.isEmpty()) {
+            persistentDataContainer = chunk.persistentDataContainer.toTagCompound();
+        }
+
+        return new SerializableChunkData(access.lookupOrThrow(Registries.BIOME), chunk.getPos(),
+                chunk.getMinSectionY(), 0, chunk.getInhabitedTime(), chunk.getPersistedStatus(),
+                Optionull.map(chunk.getBlendingData(), BlendingData::pack), chunk.getBelowZeroRetrogen(),
+                chunk.getUpgradeData().copy(), null, heightMap, packedTicks, postProcessing,
+                chunk.isLightCorrect(), list, new ArrayList<>(), blockEntities, structureData, persistentDataContainer)
+                .write();
+    }
+}

nms/v1_21_R3/src/main/java/com/volmit/iris/core/nms/v1_21_R3/NMSBinding.java

@@ -8,6 +8,8 @@ import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
 import com.volmit.iris.core.nms.container.Pair;
 import com.volmit.iris.core.nms.datapack.DataVersion;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
+import com.volmit.iris.core.nms.v1_21_R3.headless.RegionStorage;
 import com.volmit.iris.engine.data.cache.AtomicCache;
 import com.volmit.iris.engine.framework.Engine;
 import com.volmit.iris.util.collection.KList;
@@ -39,7 +41,9 @@ import net.minecraft.tags.TagKey;
 import net.minecraft.world.entity.EntityType;
 import net.minecraft.world.item.component.CustomData;
 import net.minecraft.world.level.LevelReader;
+import net.minecraft.world.level.biome.Biomes;
 import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.EntityBlock;
 import net.minecraft.world.level.block.entity.BlockEntity;
 import net.minecraft.world.level.block.state.BlockState;
@@ -49,6 +53,9 @@ import net.minecraft.world.level.chunk.status.ChunkStatus;
 import net.minecraft.world.level.chunk.status.WorldGenContext;
 import net.minecraft.world.level.dimension.DimensionType;
 import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.FlatLevelSource;
+import net.minecraft.world.level.levelgen.flat.FlatLayerInfo;
+import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
 import org.bukkit.*;
 import org.bukkit.block.Biome;
 import org.bukkit.block.data.BlockData;
@@ -659,6 +666,11 @@ public class NMSBinding implements INMSBinding {
         return keys;
     }
 
+    @Override
+    public IRegionStorage createRegionStorage(Engine engine) {
+        return new RegionStorage(engine);
+    }
+
     @Override
     public AutoClosing injectLevelStems() {
         return inject(this::supplier);
@@ -693,6 +705,15 @@ public class NMSBinding implements INMSBinding {
                 }));
     }
 
+    @Override
+    public boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end) {
+        var registry = registry().lookupOrThrow(Registries.DIMENSION_TYPE);
+        if (overworld) overworld = !registry.containsKey(createIrisKey(LevelStem.OVERWORLD));
+        if (nether) nether = !registry.containsKey(createIrisKey(LevelStem.NETHER));
+        if (end) end = !registry.containsKey(createIrisKey(LevelStem.END));
+        return overworld || nether || end;
+    }
+
     private WorldLoader.DataLoadContext supplier(WorldLoader.DataLoadContext old) {
         return dataLoadContext.aquire(() -> new WorldLoader.DataLoadContext(
                 old.resources(),
@@ -723,23 +744,32 @@ public class NMSBinding implements INMSBinding {
     private RegistryAccess.Frozen createRegistryAccess(RegistryAccess.Frozen datapack, boolean copy, boolean overworld, boolean nether, boolean end) {
         var access = registry();
         var dimensions = access.lookupOrThrow(Registries.DIMENSION_TYPE);
-        var levelStems = access.lookupOrThrow(Registries.LEVEL_STEM);
 
+        var settings = new FlatLevelGeneratorSettings(
+                Optional.empty(),
+                access.lookupOrThrow(Registries.BIOME).getOrThrow(Biomes.THE_VOID),
+                List.of()
+        );
+        settings.getLayersInfo().add(new FlatLayerInfo(1, Blocks.AIR));
+        settings.updateLayers();
+
+        var source = new FlatLevelSource(settings);
         var fake = new MappedRegistry<>(Registries.LEVEL_STEM, Lifecycle.experimental());
-        if (overworld) register(fake, levelStems, dimensions, LevelStem.OVERWORLD);
+        if (overworld) register(fake, dimensions, source, LevelStem.OVERWORLD);
-        if (nether) register(fake, levelStems, dimensions, LevelStem.NETHER);
+        if (nether) register(fake, dimensions, source, LevelStem.NETHER);
-        if (end) register(fake, levelStems, dimensions, LevelStem.END);
+        if (end) register(fake, dimensions, source, LevelStem.END);
         copy(fake, datapack.lookup(Registries.LEVEL_STEM).orElse(null));
 
-        if (copy) copy(fake, levelStems);
+        if (copy) copy(fake, access.lookupOrThrow(Registries.LEVEL_STEM));
 
         return new RegistryAccess.Frozen.ImmutableRegistryAccess(List.of(fake.freeze())).freeze();
     }
 
-    private void register(MappedRegistry<LevelStem> target, Registry<LevelStem> levelStems, Registry<DimensionType> dimensions, ResourceKey<LevelStem> key) {
+    private void register(MappedRegistry<LevelStem> target, Registry<DimensionType> dimensions, FlatLevelSource source, ResourceKey<LevelStem> key) {
+        var loc = createIrisKey(key);
         target.register(key, new LevelStem(
-                dimensions.get(ResourceLocation.fromNamespaceAndPath("iris", key.location().getPath())).orElseThrow(),
+                dimensions.get(loc).orElseThrow(() -> new IllegalStateException("Missing dimension type " + loc + " in " + dimensions.keySet())),
-                levelStems.getValueOrThrow(key).generator()
+                source
         ), RegistrationInfo.BUILT_IN);
     }
 
@@ -752,4 +782,8 @@ public class NMSBinding implements INMSBinding {
                 target.register(key, value, info);
         });
     }
+
+    private ResourceLocation createIrisKey(ResourceKey<LevelStem> key) {
+        return ResourceLocation.fromNamespaceAndPath("iris", key.location().getPath());
+    }
 }

nms/v1_21_R3/src/main/java/com/volmit/iris/core/nms/v1_21_R3/headless/DirectTerrainChunk.java

@@ -0,0 +1,211 @@
+package com.volmit.iris.core.nms.v1_21_R3.headless;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.BiomeBaseInjector;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.util.data.IrisCustomData;
+import com.volmit.iris.util.math.Position2;
+import lombok.Data;
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.EntityBlock;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import org.bukkit.Material;
+import org.bukkit.block.Biome;
+import org.bukkit.block.data.BlockData;
+import org.bukkit.craftbukkit.v1_21_R3.block.CraftBiome;
+import org.bukkit.craftbukkit.v1_21_R3.block.CraftBlockType;
+import org.bukkit.craftbukkit.v1_21_R3.block.data.CraftBlockData;
+import org.bukkit.craftbukkit.v1_21_R3.util.CraftMagicNumbers;
+import org.bukkit.generator.ChunkGenerator;
+import org.bukkit.material.MaterialData;
+import org.jetbrains.annotations.NotNull;
+
+@Data
+public final class DirectTerrainChunk implements SerializableChunk {
+    private final ProtoChunk access;
+    private final int minHeight, maxHeight;
+
+    public DirectTerrainChunk(ProtoChunk access) {
+        this.access = access;
+        this.minHeight = access.getMinY();
+        this.maxHeight = access.getMaxY();
+    }
+
+    @Override
+    public BiomeBaseInjector getBiomeBaseInjector() {
+        return null;
+    }
+
+    @NotNull
+    @Override
+    public Biome getBiome(int x, int z) {
+        return getBiome(x, 0, z);
+    }
+
+    @NotNull
+    @Override
+    public Biome getBiome(int x, int y, int z) {
+        if (y < minHeight || y > maxHeight) return Biome.PLAINS;
+        return CraftBiome.minecraftHolderToBukkit(access.getNoiseBiome(x >> 2, y >> 2, z >> 2));
+    }
+
+    @Override
+    public void setBiome(int x, int z, Biome bio) {
+        for (int y = minHeight; y < maxHeight; y += 4) {
+            setBiome(x, y, z, bio);
+        }
+    }
+
+    @Override
+    public void setBiome(int x, int y, int z, Biome bio) {
+        if (y < minHeight || y > maxHeight) return;
+        access.setBiome(x & 15, y, z & 15, CraftBiome.bukkitToMinecraftHolder(bio));
+    }
+
+    public void setBlock(int x, int y, int z, Material material) {
+        this.setBlock(x, y, z, material.createBlockData());
+    }
+
+    public void setBlock(int x, int y, int z, MaterialData material) {
+        this.setBlock(x, y, z, CraftMagicNumbers.getBlock(material));
+    }
+
+    @Override
+    public void setBlock(int x, int y, int z, BlockData blockData) {
+        if (blockData == null) {
+            Iris.error("NULL BD");
+        }
+        if (blockData instanceof IrisCustomData data)
+            blockData = data.getBase();
+        if (!(blockData instanceof CraftBlockData craftBlockData))
+            throw new IllegalArgumentException("Expected CraftBlockData, got " + blockData.getClass().getSimpleName() + " instead");
+        access.setBlockState(new BlockPos(x & 15, y, z & 15), craftBlockData.getState(), false);
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, Material material) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, material.createBlockData());
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, MaterialData material) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, CraftMagicNumbers.getBlock(material));
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, BlockData blockData) {
+        this.setRegion(xMin, yMin, zMin, xMax, yMax, zMax, ((CraftBlockData) blockData).getState());
+    }
+
+    public Material getType(int x, int y, int z) {
+        return CraftBlockType.minecraftToBukkit(this.getTypeId(x, y, z).getBlock());
+    }
+
+    public MaterialData getTypeAndData(int x, int y, int z) {
+        return CraftMagicNumbers.getMaterial(this.getTypeId(x, y, z));
+    }
+
+    public BlockData getBlockData(int x, int y, int z) {
+        return CraftBlockData.fromData(this.getTypeId(x, y, z));
+    }
+
+    @Override
+    public ChunkGenerator.ChunkData getRaw() {
+        return null;
+    }
+
+    @Override
+    public void setRaw(ChunkGenerator.ChunkData data) {
+
+    }
+
+    @Override
+    public void inject(ChunkGenerator.BiomeGrid biome) {
+
+    }
+
+    public void setRegion(int xMin, int yMin, int zMin, int xMax, int yMax, int zMax, BlockState type) {
+        if (xMin > 15 || yMin >= this.maxHeight || zMin > 15)
+            return;
+
+        if (xMin < 0) {
+            xMin = 0;
+        }
+
+        if (yMin < this.minHeight) {
+            yMin = this.minHeight;
+        }
+
+        if (zMin < 0) {
+            zMin = 0;
+        }
+
+        if (xMax > 16) {
+            xMax = 16;
+        }
+
+        if (yMax > this.maxHeight) {
+            yMax = this.maxHeight;
+        }
+
+        if (zMax > 16) {
+            zMax = 16;
+        }
+
+        if (xMin >= xMax || yMin >= yMax || zMin >= zMax)
+            return;
+
+        for (int y = yMin; y < yMax; ++y) {
+            for (int x = xMin; x < xMax; ++x) {
+                for (int z = zMin; z < zMax; ++z) {
+                    this.setBlock(x, y, z, type);
+                }
+            }
+        }
+
+    }
+
+    public BlockState getTypeId(int x, int y, int z) {
+        if (x != (x & 15) || y < this.minHeight || y >= this.maxHeight || z != (z & 15))
+            return Blocks.AIR.defaultBlockState();
+        return access.getBlockState(new BlockPos(access.getPos().getMinBlockX() + x, y, access.getPos().getMinBlockZ() + z));
+    }
+
+    public byte getData(int x, int y, int z) {
+        return CraftMagicNumbers.toLegacyData(this.getTypeId(x, y, z));
+    }
+
+    private void setBlock(int x, int y, int z, BlockState type) {
+        if (x != (x & 15) || y < this.minHeight || y >= this.maxHeight || z != (z & 15))
+            return;
+        BlockPos blockPosition = new BlockPos(access.getPos().getMinBlockX() + x, y, access.getPos().getMinBlockZ() + z);
+        BlockState oldBlockData = access.setBlockState(blockPosition, type, false);
+        if (type.hasBlockEntity()) {
+            BlockEntity tileEntity = ((EntityBlock) type.getBlock()).newBlockEntity(blockPosition, type);
+            if (tileEntity == null) {
+                access.removeBlockEntity(blockPosition);
+            } else {
+                access.setBlockEntity(tileEntity);
+            }
+        } else if (oldBlockData != null && oldBlockData.hasBlockEntity()) {
+            access.removeBlockEntity(blockPosition);
+        }
+
+    }
+
+    @Override
+    public Position2 getPos() {
+        return new Position2(access.getPos().x, access.getPos().z);
+    }
+
+    @Override
+    public Object serialize() {
+        return RegionStorage.serialize(access);
+    }
+
+    @Override
+    public void mark() {
+        access.setPersistedStatus(ChunkStatus.FULL);
+    }
+}

nms/v1_21_R3/src/main/java/com/volmit/iris/core/nms/v1_21_R3/headless/Region.java

@@ -0,0 +1,75 @@
+package com.volmit.iris.core.nms.v1_21_R3.headless;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.headless.IRegion;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.util.math.M;
+import lombok.NonNull;
+import lombok.Synchronized;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.NbtIo;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.chunk.storage.RegionFile;
+import net.minecraft.world.level.chunk.storage.RegionStorageInfo;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.nio.file.Path;
+
+class Region implements IRegion, Comparable<Region> {
+    private static final RegionStorageInfo info = new RegionStorageInfo("headless", Level.OVERWORLD, "headless");
+    private final RegionFile regionFile;
+    transient long references;
+    transient long lastUsed;
+
+    Region(Path path, Path folder) throws IOException {
+        this.regionFile = new RegionFile(info, path, folder, false);
+    }
+
+    @Override
+    @Synchronized
+    public boolean exists(int x, int z) {
+        try (DataInputStream din = regionFile.getChunkDataInputStream(new ChunkPos(x, z))) {
+            if (din == null) return false;
+            return !"empty".equals(NbtIo.read(din).getString("Status"));
+        } catch (IOException e) {
+            return false;
+        }
+    }
+
+    @Override
+    @Synchronized
+    public void write(@NonNull SerializableChunk chunk) throws IOException {
+        try (DataOutputStream dos = regionFile.getChunkDataOutputStream(chunk.getPos().convert(ChunkPos::new))) {
+            NbtIo.write((CompoundTag) chunk.serialize(), dos);
+        }
+    }
+
+    @Override
+    public void close() {
+        --references;
+        lastUsed = M.ms();
+    }
+
+    public boolean unused() {
+        return references <= 0;
+    }
+
+    public boolean remove() {
+        if (!unused()) return false;
+        try {
+            regionFile.close();
+        } catch (IOException e) {
+            Iris.error("Failed to close region file");
+            e.printStackTrace();
+        }
+        return true;
+    }
+
+    @Override
+    public int compareTo(Region o) {
+        return Long.compare(lastUsed, o.lastUsed);
+    }
+}

nms/v1_21_R3/src/main/java/com/volmit/iris/core/nms/v1_21_R3/headless/RegionStorage.java

@@ -0,0 +1,244 @@
+package com.volmit.iris.core.nms.v1_21_R3.headless;
+
+import com.volmit.iris.Iris;
+import com.volmit.iris.core.nms.headless.IRegion;
+import com.volmit.iris.core.nms.headless.IRegionStorage;
+import com.volmit.iris.core.nms.headless.SerializableChunk;
+import com.volmit.iris.engine.data.cache.AtomicCache;
+import com.volmit.iris.engine.data.cache.Cache;
+import com.volmit.iris.engine.framework.Engine;
+import com.volmit.iris.engine.object.IrisBiome;
+import com.volmit.iris.util.collection.KMap;
+import com.volmit.iris.util.context.ChunkContext;
+import com.volmit.iris.util.math.RNG;
+import com.volmit.iris.util.scheduling.J;
+import it.unimi.dsi.fastutil.shorts.ShortArrayList;
+import it.unimi.dsi.fastutil.shorts.ShortList;
+import lombok.Getter;
+import lombok.NonNull;
+import net.minecraft.FileUtil;
+import net.minecraft.Optionull;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.UpgradeData;
+import net.minecraft.world.level.chunk.storage.SerializableChunkData;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.blending.BlendingData;
+import org.bukkit.Bukkit;
+import org.bukkit.craftbukkit.v1_21_R3.CraftServer;
+import org.bukkit.craftbukkit.v1_21_R3.block.CraftBiome;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.*;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+public class RegionStorage implements IRegionStorage, LevelHeightAccessor {
+    private static final AtomicCache<RegistryAccess> CACHE = new AtomicCache<>();
+    private final KMap<Long, Region> regions = new KMap<>();
+    private final Path folder;
+
+    private final Engine engine;
+    private final KMap<String, Holder<Biome>> customBiomes = new KMap<>();
+    private final KMap<org.bukkit.block.Biome, Holder<Biome>> minecraftBiomes;
+    private final RNG biomeRng;
+    private final @Getter int minY;
+    private final @Getter int height;
+
+    private transient boolean closed = false;
+
+    public RegionStorage(Engine engine) {
+        this.engine = engine;
+        this.folder = new File(engine.getWorld().worldFolder(), "region").toPath();
+        this.biomeRng = new RNG(engine.getSeedManager().getBiome());
+
+        this.minY = engine.getDimension().getMinHeight();
+        this.height = engine.getDimension().getMaxHeight() - minY;
+
+        AtomicInteger failed = new AtomicInteger();
+        var dimKey = engine.getDimension().getLoadKey();
+        for (var biome : engine.getAllBiomes()) {
+            if (!biome.isCustom()) continue;
+            for (var custom : biome.getCustomDerivitives()) {
+                biomeHolder(dimKey, custom.getId()).ifPresentOrElse(holder -> customBiomes.put(custom.getId(), holder), () -> {
+                    Iris.error("Failed to load custom biome " + dimKey + " " + custom.getId());
+                    failed.incrementAndGet();
+                });
+            }
+        }
+        if (failed.get() > 0) {
+            throw new IllegalStateException("Failed to load " + failed.get() + " custom biomes");
+        }
+
+        minecraftBiomes = new KMap<>(org.bukkit.Registry.BIOME.stream()
+                .collect(Collectors.toMap(Function.identity(), CraftBiome::bukkitToMinecraftHolder)));
+        minecraftBiomes.values().removeAll(customBiomes.values());
+    }
+
+    @Override
+    public boolean exists(int x, int z) {
+        try (IRegion region = getRegion(x >> 5, z >> 5, true)) {
+            return region != null && region.exists(x, z);
+        } catch (Exception e) {
+            return false;
+        }
+    }
+
+    @Override
+    public IRegion getRegion(int x, int z, boolean existingOnly) throws IOException {
+        AtomicReference<IOException> exception = new AtomicReference<>();
+        Region region = regions.computeIfAbsent(Cache.key(x, z), k -> {
+            trim();
+
+            try {
+                FileUtil.createDirectoriesSafe(this.folder);
+                Path path = folder.resolve("r." + x + "." + z + ".mca");
+                if (existingOnly && !Files.exists(path)) {
+                    return null;
+                } else {
+                    return new Region(path, this.folder);
+                }
+            } catch (IOException e) {
+                exception.set(e);
+                return null;
+            }
+        });
+
+        if (region == null) {
+            if (exception.get() != null)
+                throw exception.get();
+            return null;
+        }
+        region.references++;
+        return region;
+    }
+
+    @NotNull
+    @Override
+    public SerializableChunk createChunk(int x, int z) {
+        return new DirectTerrainChunk(new ProtoChunk(new ChunkPos(x, z), UpgradeData.EMPTY, this, registryAccess().lookupOrThrow(Registries.BIOME), null));
+    }
+
+    @Override
+    public void fillBiomes(@NonNull SerializableChunk chunk, @Nullable ChunkContext ctx) {
+        if (!(chunk instanceof DirectTerrainChunk tc))
+            return;
+        tc.getAccess().fillBiomesFromNoise((qX, qY, qZ, sampler) -> getNoiseBiome(engine, ctx, qX << 2, qY << 2, qZ << 2), null);
+    }
+
+    @Override
+    public synchronized void close() {
+        if (closed) return;
+
+        while (!regions.isEmpty()) {
+            regions.values().removeIf(Region::remove);
+            J.sleep(1);
+        }
+
+        closed = true;
+        customBiomes.clear();
+        minecraftBiomes.clear();
+    }
+
+    private void trim() {
+        int size = regions.size();
+        if (size < 256) return;
+        int remove = size - 255;
+
+        var list = regions.values()
+                .stream()
+                .filter(Region::unused)
+                .sorted()
+                .collect(Collectors.toList())
+                .reversed();
+
+        int skip = list.size() - remove;
+        if (skip > 0) list.subList(0, skip).clear();
+
+        if (list.isEmpty()) return;
+        regions.values().removeIf(r -> list.contains(r) && r.remove());
+    }
+
+    private Holder<Biome> getNoiseBiome(Engine engine, ChunkContext ctx, int x, int y, int z) {
+        int m = y - engine.getMinHeight();
+        IrisBiome ib = ctx == null ? engine.getSurfaceBiome(x, z) : ctx.getBiome().get(x & 15, z & 15);
+        if (ib.isCustom()) {
+            return customBiomes.get(ib.getCustomBiome(biomeRng, x, m, z).getId());
+        } else {
+            return minecraftBiomes.get(ib.getSkyBiome(biomeRng, x, m, z));
+        }
+    }
+
+    private static RegistryAccess registryAccess() {
+        return CACHE.aquire(() -> ((CraftServer) Bukkit.getServer()).getServer().registryAccess());
+    }
+
+    private static Optional<Holder.Reference<Biome>> biomeHolder(String namespace, String path) {
+        return registryAccess().lookupOrThrow(Registries.BIOME).get(ResourceLocation.fromNamespaceAndPath(namespace, path));
+    }
+
+    static CompoundTag serialize(ChunkAccess chunk) {
+        RegistryAccess access = registryAccess();
+        List<SerializableChunkData.SectionData> list = new ArrayList<>();
+        LevelChunkSection[] sections = chunk.getSections();
+
+        int minLightSection = chunk.getMinSectionY() - 1;
+        int maxLightSection = minLightSection + chunk.getSectionsCount() + 2;
+        for(int y = minLightSection; y < maxLightSection; ++y) {
+            int index = chunk.getSectionIndexFromSectionY(y);
+            if (index < 0 || index >= sections.length) continue;
+            LevelChunkSection section = sections[index].copy();
+            list.add(new SerializableChunkData.SectionData(y, section, null, null));
+        }
+
+        List<CompoundTag> blockEntities = new ArrayList<>(chunk.getBlockEntitiesPos().size());
+
+        for(BlockPos blockPos : chunk.getBlockEntitiesPos()) {
+            CompoundTag nbt = chunk.getBlockEntityNbtForSaving(blockPos, access);
+            if (nbt != null) {
+                blockEntities.add(nbt);
+            }
+        }
+        Map<Heightmap.Types, long[]> heightMap = new EnumMap<>(Heightmap.Types.class);
+        for(Map.Entry<Heightmap.Types, Heightmap> entry : chunk.getHeightmaps()) {
+            if (chunk.getPersistedStatus().heightmapsAfter().contains(entry.getKey())) {
+                heightMap.put(entry.getKey(), entry.getValue().getRawData().clone());
+            }
+        }
+
+        ChunkAccess.PackedTicks packedTicks = chunk.getTicksForSerialization(0);
+        ShortList[] postProcessing = Arrays.stream(chunk.getPostProcessing()).map((shortlist) -> shortlist != null ? new ShortArrayList(shortlist) : null).toArray(ShortList[]::new);
+        CompoundTag structureData = new CompoundTag();
+        structureData.put("starts", new CompoundTag());
+        structureData.put("References", new CompoundTag());
+
+        CompoundTag persistentDataContainer = null;
+        if (!chunk.persistentDataContainer.isEmpty()) {
+            persistentDataContainer = chunk.persistentDataContainer.toTagCompound();
+        }
+
+        return new SerializableChunkData(access.lookupOrThrow(Registries.BIOME), chunk.getPos(),
+                chunk.getMinSectionY(), 0, chunk.getInhabitedTime(), chunk.getPersistedStatus(),
+                Optionull.map(chunk.getBlendingData(), BlendingData::pack), chunk.getBelowZeroRetrogen(),
+                chunk.getUpgradeData().copy(), null, heightMap, packedTicks, postProcessing,
+                chunk.isLightCorrect(), list, new ArrayList<>(), blockEntities, structureData, persistentDataContainer)
+                .write();
+    }
+}