f

core/src/main/java/art/arcane/iris/core/ServerConfigurator.java

@@ -27,7 +27,6 @@ import art.arcane.iris.engine.object.*;
 import art.arcane.volmlib.util.collection.KList;
 import art.arcane.volmlib.util.collection.KMap;
 import art.arcane.volmlib.util.collection.KSet;
-import art.arcane.volmlib.util.io.IO;
 import art.arcane.iris.util.common.format.C;
 import art.arcane.iris.util.common.misc.ServerProperties;
 import art.arcane.iris.util.common.plugin.VolmitSender;
@@ -42,8 +41,6 @@ import org.jetbrains.annotations.Nullable;
 
 import java.io.File;
 import java.io.IOException;
-import java.nio.file.Files;
-import java.nio.file.StandardCopyOption;
 import java.util.Arrays;
 import java.util.Objects;
 import java.util.concurrent.TimeUnit;
@@ -147,42 +144,24 @@ public class ServerConfigurator {
 
         File source = Iris.instance.getDataFolder("datapacks");
         source.mkdirs();
-        File[] datapacks = source.listFiles();
-        if (datapacks == null || datapacks.length == 0) {
-            return;
+        ExternalDataPackPipeline.syncPinnedDatapacks(source);
+        int removedLegacyCopies = ExternalDataPackPipeline.removeLegacyWorldDatapackCopies(source, folders);
+        ExternalDataPackPipeline.ImportSummary summary = ExternalDataPackPipeline.importDatapackStructures(source);
+        if (removedLegacyCopies > 0) {
+            Iris.info("Removed " + removedLegacyCopies + " legacy external datapack world copies.");
         }
-
-        int copied = 0;
-        for (File targetFolder : folders) {
-            targetFolder.mkdirs();
-            for (File entry : datapacks) {
-                if (entry == null || !entry.exists() || entry.getName().startsWith(".")) {
-                    continue;
-                }
-
-                File output = new File(targetFolder, entry.getName());
-                try {
-                    if (entry.isDirectory()) {
-                        IO.copyDirectory(entry.toPath(), output.toPath());
-                    } else if (entry.isFile()) {
-                        File parent = output.getParentFile();
-                        if (parent != null) {
-                            parent.mkdirs();
-                        }
-                        Files.copy(entry.toPath(), output.toPath(), StandardCopyOption.REPLACE_EXISTING);
-                    } else {
-                        continue;
-                    }
-                    copied++;
-                } catch (Throwable e) {
-                    Iris.warn("Failed to install datapack \"" + entry.getName() + "\" into \"" + targetFolder.getPath() + "\"");
-                    Iris.reportError(e);
-                }
-            }
+        if (summary.getSources() > 0) {
+            Iris.info("External datapack structure import: sources=" + summary.getSources()
+                    + ", cached=" + summary.getCachedSources()
+                    + ", scanned=" + summary.getNbtScanned()
+                    + ", converted=" + summary.getConverted()
+                    + ", failed=" + summary.getFailed()
+                    + ", skipped=" + summary.getSkipped()
+                    + ", entitiesIgnored=" + summary.getEntitiesIgnored()
+                    + ", blockEntities=" + summary.getBlockEntities());
         }
-
-        if (copied > 0) {
-            Iris.info("Installed " + copied + " external datapack copy operation" + (copied == 1 ? "" : "s") + " from " + source.getPath());
+        if (summary.getSources() > 0 || summary.getConverted() > 0) {
+            Iris.info("External datapack world install is disabled; only structure template import is applied.");
         }
     }
 

core/src/main/java/art/arcane/iris/engine/framework/Engine.java

@@ -222,7 +222,7 @@ public interface Engine extends DataProvider, Fallible, LootProvider, BlockUpdat
             }
         }
 
-        return getCaveBiome(x, z);
+        return getCaveBiome(x, y, z);
     }
 
     @ChunkCoordinates
@@ -236,6 +236,28 @@ public interface Engine extends DataProvider, Fallible, LootProvider, BlockUpdat
         return getComplex().getCaveBiomeStream().get(x, z);
     }
 
+    @BlockCoordinates
+    default IrisBiome getCaveBiome(int x, int y, int z) {
+        IrisBiome caveBiome = getCaveBiome(x, z);
+        IrisBiome surfaceBiome = getSurfaceBiome(x, z);
+        if (caveBiome == null) {
+            return surfaceBiome;
+        }
+
+        int surfaceY = getComplex().getHeightStream().get(x, z).intValue();
+        int depthBelowSurface = surfaceY - y;
+        if (depthBelowSurface <= 0) {
+            return surfaceBiome;
+        }
+
+        int minDepth = Math.max(0, caveBiome.getCaveMinDepthBelowSurface());
+        if (depthBelowSurface < minDepth) {
+            return surfaceBiome;
+        }
+
+        return caveBiome;
+    }
+
     @BlockCoordinates
     default IrisBiome getSurfaceBiome(int x, int z) {
         return getComplex().getTrueBiomeStream().get(x, z);
@@ -514,7 +536,7 @@ public interface Engine extends DataProvider, Fallible, LootProvider, BlockUpdat
 
         IrisRegion region = getComplex().getRegionStream().get(rx, rz);
         IrisBiome biomeSurface = getComplex().getTrueBiomeStream().get(rx, rz);
-        IrisBiome biomeUnder = ry < he ? getComplex().getCaveBiomeStream().get(rx, rz) : biomeSurface;
+        IrisBiome biomeUnder = ry < he ? getCaveBiome(rx, ry, rz) : biomeSurface;
 
         double multiplier = 1D * getDimension().getLoot().getMultiplier() * region.getLoot().getMultiplier() * biomeSurface.getLoot().getMultiplier() * biomeUnder.getLoot().getMultiplier();
         boolean fallback = tables.isEmpty();
@@ -796,7 +818,7 @@ public interface Engine extends DataProvider, Fallible, LootProvider, BlockUpdat
 
     default IrisBiome getBiome(int x, int y, int z) {
         if (y <= getHeight(x, z) - 2) {
-            return getCaveBiome(x, z);
+            return getCaveBiome(x, y, z);
         }
 
         return getSurfaceBiome(x, z);

core/src/main/java/art/arcane/iris/engine/mantle/components/IrisCaveCarver3D.java

@@ -98,35 +98,132 @@ public class IrisCaveCarver3D {
 
         int x0 = chunkX << 4;
         int z0 = chunkZ << 4;
+        int[] columnSurface = new int[256];
+        int[] columnMaxY = new int[256];
+        int[] surfaceBreakFloorY = new int[256];
+        boolean[] surfaceBreakColumn = new boolean[256];
+        double[] columnThreshold = new double[256];
+
+        for (int lx = 0; lx < 16; lx++) {
+            int x = x0 + lx;
+            for (int lz = 0; lz < 16; lz++) {
+                int z = z0 + lz;
+                int index = (lx << 4) | lz;
+                int columnSurfaceY = engine.getHeight(x, z);
+                int clearanceTopY = Math.min(maxY, Math.max(minY, columnSurfaceY - surfaceClearance));
+                boolean breakColumn = allowSurfaceBreak
+                        && signed(surfaceBreakDensity.noise(x, z)) >= surfaceBreakNoiseThreshold;
+                int columnTopY = breakColumn
+                        ? Math.min(maxY, Math.max(minY, columnSurfaceY))
+                        : clearanceTopY;
+
+                columnSurface[index] = columnSurfaceY;
+                columnMaxY[index] = columnTopY;
+                surfaceBreakFloorY[index] = Math.max(minY, columnSurfaceY - surfaceBreakDepth);
+                surfaceBreakColumn[index] = breakColumn;
+                columnThreshold[index] = profile.getDensityThreshold().get(thresholdRng, x, z, data) - profile.getThresholdBias();
+            }
+        }
+
+        int carved = carvePass(
+                writer,
+                x0,
+                z0,
+                minY,
+                maxY,
+                sampleStep,
+                surfaceBreakThresholdBoost,
+                waterMinDepthBelowSurface,
+                waterRequiresFloor,
+                columnSurface,
+                columnMaxY,
+                surfaceBreakFloorY,
+                surfaceBreakColumn,
+                columnThreshold,
+                0D,
+                false
+        );
+
+        int minCarveCells = Math.max(0, profile.getMinCarveCells());
+        double recoveryThresholdBoost = Math.max(0, profile.getRecoveryThresholdBoost());
+        if (carved < minCarveCells && recoveryThresholdBoost > 0D) {
+            carved += carvePass(
+                    writer,
+                    x0,
+                    z0,
+                    minY,
+                    maxY,
+                    sampleStep,
+                    surfaceBreakThresholdBoost,
+                    waterMinDepthBelowSurface,
+                    waterRequiresFloor,
+                    columnSurface,
+                    columnMaxY,
+                    surfaceBreakFloorY,
+                    surfaceBreakColumn,
+                    columnThreshold,
+                    recoveryThresholdBoost,
+                    true
+            );
+        }
+
+        return carved;
+    }
+
+    private int carvePass(
+            MantleWriter writer,
+            int x0,
+            int z0,
+            int minY,
+            int maxY,
+            int sampleStep,
+            double surfaceBreakThresholdBoost,
+            int waterMinDepthBelowSurface,
+            boolean waterRequiresFloor,
+            int[] columnSurface,
+            int[] columnMaxY,
+            int[] surfaceBreakFloorY,
+            boolean[] surfaceBreakColumn,
+            double[] columnThreshold,
+            double thresholdBoost,
+            boolean skipExistingCarved
+    ) {
         int carved = 0;
 
-        for (int x = x0; x < x0 + 16; x++) {
-            for (int z = z0; z < z0 + 16; z++) {
-                double threshold = profile.getDensityThreshold().get(thresholdRng, x, z, data) - profile.getThresholdBias();
-                int columnSurface = engine.getHeight(x, z);
-                int clearanceTopY = Math.min(maxY, Math.max(minY, columnSurface - surfaceClearance));
-                boolean surfaceBreakColumn = allowSurfaceBreak
-                        && signed(surfaceBreakDensity.noise(x, z)) >= surfaceBreakNoiseThreshold;
-                int columnMaxY = surfaceBreakColumn
-                        ? Math.min(maxY, Math.max(minY, columnSurface))
-                        : clearanceTopY;
-                int surfaceBreakFloorY = Math.max(minY, columnSurface - surfaceBreakDepth);
-                if (columnMaxY < minY) {
+        for (int lx = 0; lx < 16; lx++) {
+            int x = x0 + lx;
+            for (int lz = 0; lz < 16; lz++) {
+                int z = z0 + lz;
+                int index = (lx << 4) | lz;
+                int columnTopY = columnMaxY[index];
+                if (columnTopY < minY) {
                     continue;
                 }
 
-                for (int y = minY; y <= columnMaxY; y += sampleStep) {
+                boolean breakColumn = surfaceBreakColumn[index];
+                int breakFloorY = surfaceBreakFloorY[index];
+                int surfaceY = columnSurface[index];
+                double threshold = columnThreshold[index] + thresholdBoost;
+
+                for (int y = minY; y <= columnTopY; y += sampleStep) {
                     double localThreshold = threshold;
-                    if (surfaceBreakColumn && y >= surfaceBreakFloorY) {
+                    if (breakColumn && y >= breakFloorY) {
                         localThreshold += surfaceBreakThresholdBoost;
                     }
 
-                    if (sampleDensity(x, y, z) <= localThreshold) {
-                        int carveMaxY = Math.min(columnMaxY, y + sampleStep - 1);
-                        for (int yy = y; yy <= carveMaxY; yy++) {
-                            writer.setData(x, yy, z, resolveMatter(x, yy, z, localThreshold, waterMinDepthBelowSurface, waterRequiresFloor));
-                            carved++;
+                    localThreshold = applyVerticalEdgeFade(localThreshold, y, minY, maxY);
+                    if (sampleDensity(x, y, z) > localThreshold) {
+                        continue;
+                    }
+
+                    int carveMaxY = Math.min(columnTopY, y + sampleStep - 1);
+                    for (int yy = y; yy <= carveMaxY; yy++) {
+                        if (skipExistingCarved && writer.isCarved(x, yy, z)) {
+                            continue;
                         }
+
+                        writer.setData(x, yy, z, resolveMatter(x, yy, z, surfaceY, localThreshold, waterMinDepthBelowSurface, waterRequiresFloor));
+                        carved++;
                     }
                 }
             }
@@ -135,6 +232,25 @@ public class IrisCaveCarver3D {
         return carved;
     }
 
+    private double applyVerticalEdgeFade(double threshold, int y, int minY, int maxY) {
+        int fadeRange = Math.max(0, profile.getVerticalEdgeFade());
+        if (fadeRange <= 0 || maxY <= minY) {
+            return threshold;
+        }
+
+        int floorDistance = y - minY;
+        int ceilingDistance = maxY - y;
+        int edgeDistance = Math.min(floorDistance, ceilingDistance);
+        if (edgeDistance >= fadeRange) {
+            return threshold;
+        }
+
+        double t = Math.max(0D, Math.min(1D, edgeDistance / (double) fadeRange));
+        double smooth = t * t * (3D - (2D * t));
+        double fadeStrength = Math.max(0D, profile.getVerticalEdgeFadeStrength());
+        return threshold - ((1D - smooth) * fadeStrength);
+    }
+
     private double sampleDensity(int x, int y, int z) {
         double warpedX = x;
         double warpedY = y;
@@ -142,9 +258,11 @@ public class IrisCaveCarver3D {
         double warpStrength = profile.getWarpStrength();
 
         if (warpStrength > 0) {
-            double offsetX = signed(warpDensity.noise(x, y, z)) * warpStrength;
-            double offsetY = signed(warpDensity.noise(y, z, x)) * warpStrength;
-            double offsetZ = signed(warpDensity.noise(z, x, y)) * warpStrength;
+            double warpA = signed(warpDensity.noise(x, y, z));
+            double warpB = signed(warpDensity.noise(x + 31.37D, y - 17.21D, z + 23.91D));
+            double offsetX = warpA * warpStrength;
+            double offsetY = warpB * warpStrength;
+            double offsetZ = (warpA - warpB) * 0.5D * warpStrength;
             warpedX += offsetX;
             warpedY += offsetY;
             warpedZ += offsetZ;
@@ -169,7 +287,7 @@ public class IrisCaveCarver3D {
         return density / normalization;
     }
 
-    private MatterCavern resolveMatter(int x, int y, int z, double localThreshold, int waterMinDepthBelowSurface, boolean waterRequiresFloor) {
+    private MatterCavern resolveMatter(int x, int y, int z, int surfaceY, double localThreshold, int waterMinDepthBelowSurface, boolean waterRequiresFloor) {
         int lavaHeight = engine.getDimension().getCaveLavaHeight();
         int fluidHeight = engine.getDimension().getFluidHeight();
 
@@ -178,7 +296,6 @@ public class IrisCaveCarver3D {
         }
 
         if (profile.isAllowWater() && y <= fluidHeight) {
-            int surfaceY = engine.getHeight(x, z);
             if (surfaceY - y < waterMinDepthBelowSurface) {
                 return carveAir;
             }
@@ -207,7 +324,6 @@ public class IrisCaveCarver3D {
     private boolean hasAquiferCupSupport(int x, int y, int z, double threshold) {
         int floorY = Math.max(0, y - 1);
         int deepFloorY = Math.max(0, y - 2);
-        int aboveY = Math.min(engine.getHeight() - 1, y + 1);
         if (!isDensitySolid(x, floorY, z, threshold)) {
             return false;
         }
@@ -229,11 +345,8 @@ public class IrisCaveCarver3D {
         if (isDensitySolid(x, y, z - 1, threshold)) {
             support++;
         }
-        if (isDensitySolid(x, aboveY, z, threshold)) {
-            support++;
-        }
 
-        return support >= 4;
+        return support >= 3;
     }
 
     private boolean isDensitySolid(int x, int y, int z, double threshold) {

core/src/main/java/art/arcane/iris/engine/mantle/components/MantleCarvingComponent.java

@@ -50,23 +50,47 @@ public class MantleCarvingComponent extends IrisMantleComponent {
         int xxx = 8 + (x << 4);
         int zzz = 8 + (z << 4);
         IrisRegion region = getComplex().getRegionStream().get(xxx, zzz);
-        IrisBiome biome = getComplex().getTrueBiomeStream().get(xxx, zzz);
-        carve(writer, rng, x, z, region, biome);
+        IrisBiome surfaceBiome = getComplex().getTrueBiomeStream().get(xxx, zzz);
+        IrisCaveProfile caveBiomeProfile = resolveDominantCaveBiomeProfile(x, z);
+        carve(writer, rng, x, z, region, surfaceBiome, caveBiomeProfile);
     }
 
     @ChunkCoordinates
-    private void carve(MantleWriter writer, RNG rng, int cx, int cz, IrisRegion region, IrisBiome biome) {
+    private void carve(MantleWriter writer, RNG rng, int cx, int cz, IrisRegion region, IrisBiome surfaceBiome, IrisCaveProfile caveBiomeProfile) {
         IrisCaveProfile dimensionProfile = getDimension().getCaveProfile();
-        IrisCaveProfile biomeProfile = biome.getCaveProfile();
+        IrisCaveProfile surfaceBiomeProfile = surfaceBiome.getCaveProfile();
         IrisCaveProfile regionProfile = region.getCaveProfile();
-        IrisCaveProfile activeProfile = resolveActiveProfile(dimensionProfile, regionProfile, biomeProfile);
+        IrisCaveProfile activeProfile = resolveActiveProfile(dimensionProfile, regionProfile, surfaceBiomeProfile, caveBiomeProfile);
         if (isProfileEnabled(activeProfile)) {
-            carveProfile(activeProfile, writer, cx, cz);
-            return;
+            int carved = carveProfile(activeProfile, writer, cx, cz);
+            if (carved > 0) {
+                return;
+            }
+
+            if (activeProfile != regionProfile && isProfileEnabled(regionProfile)) {
+                carved = carveProfile(regionProfile, writer, cx, cz);
+                if (carved > 0) {
+                    return;
+                }
+            }
+
+            if (activeProfile != surfaceBiomeProfile && isProfileEnabled(surfaceBiomeProfile)) {
+                carved = carveProfile(surfaceBiomeProfile, writer, cx, cz);
+                if (carved > 0) {
+                    return;
+                }
+            }
+
+            if (activeProfile != dimensionProfile && isProfileEnabled(dimensionProfile)) {
+                carved = carveProfile(dimensionProfile, writer, cx, cz);
+                if (carved > 0) {
+                    return;
+                }
+            }
         }
 
         carve(getDimension().getCarving(), writer, nextCarveRng(rng, cx, cz), cx, cz);
-        carve(biome.getCarving(), writer, nextCarveRng(rng, cx, cz), cx, cz);
+        carve(surfaceBiome.getCarving(), writer, nextCarveRng(rng, cx, cz), cx, cz);
         carve(region.getCarving(), writer, nextCarveRng(rng, cx, cz), cx, cz);
     }
 
@@ -80,13 +104,13 @@ public class MantleCarvingComponent extends IrisMantleComponent {
     }
 
     @ChunkCoordinates
-    private void carveProfile(IrisCaveProfile profile, MantleWriter writer, int cx, int cz) {
+    private int carveProfile(IrisCaveProfile profile, MantleWriter writer, int cx, int cz) {
         if (!isProfileEnabled(profile)) {
-            return;
+            return 0;
         }
 
         IrisCaveCarver3D carver = getCarver(profile);
-        carver.carve(writer, cx, cz);
+        return carver.carve(writer, cx, cz);
     }
 
     private IrisCaveCarver3D getCarver(IrisCaveProfile profile) {
@@ -106,9 +130,59 @@ public class MantleCarvingComponent extends IrisMantleComponent {
         return profile != null && profile.isEnabled();
     }
 
-    private IrisCaveProfile resolveActiveProfile(IrisCaveProfile dimensionProfile, IrisCaveProfile regionProfile, IrisCaveProfile biomeProfile) {
-        if (isProfileEnabled(biomeProfile)) {
-            return biomeProfile;
+    @ChunkCoordinates
+    private IrisCaveProfile resolveDominantCaveBiomeProfile(int chunkX, int chunkZ) {
+        int[] offsets = new int[]{1, 4, 8, 12, 15};
+        Map<IrisCaveProfile, Integer> profileVotes = new IdentityHashMap<>();
+        int validSamples = 0;
+        IrisCaveProfile dominantProfile = null;
+        int dominantVotes = 0;
+
+        for (int offsetX : offsets) {
+            for (int offsetZ : offsets) {
+                int sampleX = (chunkX << 4) + offsetX;
+                int sampleZ = (chunkZ << 4) + offsetZ;
+                int surfaceY = getEngineMantle().getEngine().getHeight(sampleX, sampleZ, true);
+                int sampleY = Math.max(1, surfaceY - 56);
+                IrisBiome caveBiome = getEngineMantle().getEngine().getCaveBiome(sampleX, sampleY, sampleZ);
+                if (caveBiome == null) {
+                    continue;
+                }
+
+                IrisCaveProfile profile = caveBiome.getCaveProfile();
+                if (!isProfileEnabled(profile)) {
+                    continue;
+                }
+
+                int votes = profileVotes.getOrDefault(profile, 0) + 1;
+                profileVotes.put(profile, votes);
+                validSamples++;
+                if (votes > dominantVotes) {
+                    dominantVotes = votes;
+                    dominantProfile = profile;
+                }
+            }
+        }
+
+        if (dominantProfile == null || validSamples <= 0) {
+            return null;
+        }
+
+        int requiredVotes = Math.max(13, (int) Math.ceil(validSamples * 0.65D));
+        if (dominantVotes < requiredVotes) {
+            return null;
+        }
+
+        return dominantProfile;
+    }
+
+    private IrisCaveProfile resolveActiveProfile(IrisCaveProfile dimensionProfile, IrisCaveProfile regionProfile, IrisCaveProfile surfaceBiomeProfile, IrisCaveProfile caveBiomeProfile) {
+        if (isProfileEnabled(caveBiomeProfile)) {
+            return caveBiomeProfile;
+        }
+
+        if (isProfileEnabled(surfaceBiomeProfile)) {
+            return surfaceBiomeProfile;
         }
 
         if (isProfileEnabled(regionProfile)) {

core/src/main/java/art/arcane/iris/engine/mantle/components/MantleObjectComponent.java

@@ -64,7 +64,12 @@ public class MantleObjectComponent extends IrisMantleComponent {
         int zzz = 8 + (z << 4);
         IrisRegion region = getComplex().getRegionStream().get(xxx, zzz);
         IrisBiome surfaceBiome = getComplex().getTrueBiomeStream().get(xxx, zzz);
-        IrisBiome caveBiome = getComplex().getCaveBiomeStream().get(xxx, zzz);
+        int surfaceY = getEngineMantle().getEngine().getHeight(xxx, zzz, true);
+        int sampleY = Math.max(1, surfaceY - 48);
+        IrisBiome caveBiome = getEngineMantle().getEngine().getCaveBiome(xxx, sampleY, zzz);
+        if (caveBiome == null) {
+            caveBiome = surfaceBiome;
+        }
         if (traceRegen) {
             Iris.info("Regen object layer start: chunk=" + x + "," + z
                     + " surfaceBiome=" + surfaceBiome.getLoadKey()

core/src/main/java/art/arcane/iris/engine/modifier/IrisCarveModifier.java

@@ -123,7 +123,7 @@ public class IrisCarveModifier extends EngineAssignedModifier<BlockData> {
 
         walls.forEach((i, v) -> {
             IrisBiome biome = v.getCustomBiome().isEmpty()
-                    ? getEngine().getCaveBiome(i.getX() + (x << 4), i.getZ() + (z << 4))
+                    ? getEngine().getCaveBiome(i.getX() + (x << 4), i.getY(), i.getZ() + (z << 4))
                     : getEngine().getData().getBiomeLoader().load(v.getCustomBiome());
 
             if (biome != null) {
@@ -207,7 +207,7 @@ public class IrisCarveModifier extends EngineAssignedModifier<BlockData> {
         }
 
         IrisBiome biome = customBiome.isEmpty()
-                ? getEngine().getCaveBiome(xx, zz)
+                ? getEngine().getCaveBiome(xx, center, zz)
                 : getEngine().getData().getBiomeLoader().load(customBiome);
 
         if (biome == null) {

core/src/main/java/art/arcane/iris/engine/object/IrisBiome.java

@@ -137,6 +137,10 @@ public class IrisBiome extends IrisRegistrant implements IRare {
     @RegistryListResource(IrisBiome.class)
     @Desc("The carving biome. If specified the biome will be used when under a carving instead of this current biome.")
     private String carvingBiome = "";
+    @MinNumber(0)
+    @MaxNumber(256)
+    @Desc("Minimum depth below terrain surface required before this cave biome can be selected.")
+    private int caveMinDepthBelowSurface = 0;
     @Desc("The default slab if iris decides to place a slab in this biome. Default is no slab.")
     private IrisBiomePaletteLayer slab = new IrisBiomePaletteLayer().zero();
     @Desc("The default wall if iris decides to place a wall higher than 2 blocks (steep hills or possibly cliffs)")

core/src/main/java/art/arcane/iris/engine/object/IrisCaveProfile.java

@@ -24,6 +24,16 @@ public class IrisCaveProfile {
     @Desc("Global vertical bounds for profile cave carving.")
     private IrisRange verticalRange = new IrisRange(0, 384);
 
+    @MinNumber(0)
+    @MaxNumber(128)
+    @Desc("Vertical fade range applied near cave profile min/max bounds to avoid abrupt hard-stop ceilings/floors.")
+    private int verticalEdgeFade = 20;
+
+    @MinNumber(0)
+    @MaxNumber(1)
+    @Desc("Strength of the vertical edge fade at cave profile min/max bounds.")
+    private double verticalEdgeFadeStrength = 0.18;
+
     @Desc("Base density style for cave field generation.")
     private IrisGeneratorStyle baseDensityStyle = NoiseStyle.CELLULAR_IRIS_DOUBLE.style();
 
@@ -58,6 +68,16 @@ public class IrisCaveProfile {
     @Desc("Vertical sample step used while evaluating cave density.")
     private int sampleStep = 2;
 
+    @MinNumber(0)
+    @MaxNumber(4096)
+    @Desc("Minimum carved cells expected from this profile before recovery boost applies.")
+    private int minCarveCells = 0;
+
+    @MinNumber(0)
+    @MaxNumber(1)
+    @Desc("Additional threshold boost used when profile carve output is too sparse.")
+    private double recoveryThresholdBoost = 0.08;
+
     @MinNumber(0)
     @MaxNumber(64)
     @Desc("Minimum solid clearance below terrain surface where carving may occur.")

nms/v1_21_R7/src/main/java/art/arcane/iris/core/nms/v1_21_R7/CustomBiomeSource.java

@@ -205,9 +205,12 @@ public class CustomBiomeSource extends BiomeSource {
         int blockZ = z << 2;
         int blockY = y << 2;
         int surfaceY = engine.getComplex().getHeightStream().get(blockX, blockZ).intValue();
-        boolean underground = blockY <= surfaceY - 2;
+        int caveSwitchY = Math.min(-8, engine.getMinHeight() + 40);
+        boolean deepUnderground = blockY <= caveSwitchY;
+        boolean belowSurface = blockY <= surfaceY - 8;
+        boolean underground = deepUnderground && belowSurface;
         IrisBiome irisBiome = underground
-                ? engine.getComplex().getCaveBiomeStream().get(blockX, blockZ)
+                ? engine.getCaveBiome(blockX, blockY, blockZ)
                 : engine.getComplex().getTrueBiomeStream().get(blockX, blockZ);
         if (irisBiome == null && underground) {
             irisBiome = engine.getComplex().getTrueBiomeStream().get(blockX, blockZ);