Merge W2A-history

core/src/main/java/art/arcane/iris/generation/runtime/Engine.java

@@ -59,6 +59,7 @@ import art.arcane.volmlib.util.documentation.BlockCoordinates;
 import art.arcane.volmlib.util.documentation.ChunkCoordinates;
 import art.arcane.volmlib.util.function.Function2;
 import art.arcane.volmlib.util.hunk.Hunk;
+import art.arcane.volmlib.util.mantle.runtime.Mantle;
 import art.arcane.volmlib.util.mantle.runtime.MantleChunk;
 import art.arcane.volmlib.util.mantle.flag.MantleFlag;
 import art.arcane.volmlib.util.math.M;
@@ -341,25 +342,101 @@ public interface Engine extends DataProvider, Fallible, BlockUpdater, Renderer,
 
     @BlockCoordinates
     default IrisBiome getCaveOrMantleBiome(int x, int y, int z) {
+        IrisBiome mantleBiome = mantleCaveBiome(x, y, z);
+        return mantleBiome != null ? mantleBiome : getCaveBiome(x, y, z);
+    }
+
+    private IrisBiome mantleCaveBiome(int x, int y, int z) {
+        IrisBiome flooded = floodedCaveBiome(x, y, z);
+        return flooded != null ? flooded : customCaveBiome(getMantle().getMantle().get(x, y, z, MatterCavern.class));
+    }
+
+    private IrisBiome floodedCaveBiome(int x, int y, int z) {
         HydrologyCaveCell hydrology = HydrologyCaveStorage.getIfPresent(
                 getMantle().getMantle(), x, y, z);
         if (hydrology != null && !hydrology.floodedBiomeKey().isEmpty()) {
-            IrisBiome biome = getData().getBiomeLoader().load(hydrology.floodedBiomeKey());
+            return getData().getBiomeLoader().load(hydrology.floodedBiomeKey());
-            if (biome != null) {
+        }
-                return biome;
+        return null;
+    }
+
+    private IrisBiome customCaveBiome(MatterCavern cavern) {
+        if (cavern != null && cavern.getCustomBiome() != null && !cavern.getCustomBiome().isEmpty()) {
+            return getData().getBiomeLoader().load(cavern.getCustomBiome());
+        }
+        return null;
+    }
+
+    private MantleChunk<Matter> useCavernChunk(int x, int z) {
+        Mantle<Matter> mantle = getMantle().getMantle();
+        int chunkX = x >> 4;
+        int chunkZ = z >> 4;
+        return mantle.hasTectonicPlate(chunkX >> 5, chunkZ >> 5) ? mantle.getChunk(chunkX, chunkZ).use() : null;
+    }
+
+    /**
+     * Fills {@code biomes[i]} with {@link #getBiomeOrMantle(int, int, int)} and {@code regions[i]} with
+     * {@link #getRegion(int, int, int)} at y = i * step of one column, resolving what does not vary along it once.
+     */
+    @BlockCoordinates
+    default void getBiomeOrMantleColumn(int x, int z, int step, IrisBiome[] biomes, IrisRegion[] regions) {
+        if (getDimensionStackContext() != null) {
+            for (int index = 0; index < biomes.length; index++) {
+                biomes[index] = getBiomeOrMantle(x, index * step, z);
+                regions[index] = getRegion(x, index * step, z);
+            }
+            return;
+        }
+        IrisComplex complex = getComplex();
+        int caveTop = getHeight(x, z) - 2;
+        IrisRegion region = getRegion(x, 0, z);
+        IrisBiome surface = null;
+        boolean cavernChunkResolved = false;
+        MantleChunk<Matter> cavernChunk = null;
+        boolean caveColumnResolved = false;
+        IrisBiome caveBase = null;
+        IrisBiome caveSurface = null;
+        int caveSurfaceY = 0;
+        try {
+            for (int index = 0; index < biomes.length; index++) {
+                int y = index * step;
+                regions[index] = region;
+                if (y > caveTop || complex.isTerrain3DSurface(x, y, z)) {
+                    if (surface == null) {
+                        surface = getSurfaceBiome(x, z);
+                    }
+                    biomes[index] = surface;
+                    continue;
+                }
+                IrisBiome biome = floodedCaveBiome(x, y, z);
+                if (biome == null) {
+                    if (!cavernChunkResolved) {
+                        cavernChunk = useCavernChunk(x, z);
+                        cavernChunkResolved = true;
+                    }
+                    biome = cavernChunk == null || y < 0 || y >= getMantle().getMantle().getWorldHeight()
+                            ? null : customCaveBiome(cavernChunk.get(x & 15, y, z & 15, MatterCavern.class));
+                }
+                if (biome == null) {
+                    biome = resolveConfiguredCaveBiome(x, y, z, null);
+                }
+                if (biome == null) {
+                    if (!caveColumnResolved) {
+                        boolean naturalFallback = answersFromNaturalTerrain(x, z);
+                        caveSurface = caveDepthSurfaceBiome(x, z, naturalFallback);
+                        caveSurfaceY = caveDepthSurfaceY(x, z, naturalFallback);
+                        caveBase = getCaveBiome(x, z);
+                        caveColumnResolved = true;
+                    }
+                    biome = depthCaveBiome(caveBase, y, caveSurface, caveSurfaceY);
+                }
+                biomes[index] = biome;
+            }
+        } finally {
+            if (cavernChunk != null) {
+                cavernChunk.release();
             }
         }
-        MatterCavern m = getMantle().getMantle().get(x, y, z, MatterCavern.class);
-
-        if (m != null && m.getCustomBiome() != null && !m.getCustomBiome().isEmpty()) {
-            IrisBiome biome = getData().getBiomeLoader().load(m.getCustomBiome());
-
-            if (biome != null) {
-                return biome;
-            }
-        }
-
-        return getCaveBiome(x, y, z);
     }
 
     @ChunkCoordinates
@@ -386,16 +463,22 @@ public interface Engine extends DataProvider, Fallible, BlockUpdater, Renderer,
             return configuredBiome;
         }
         boolean naturalFallback = answersFromNaturalTerrain(x, z);
-        DimensionStackContext dimensionStackContext = getDimensionStackContext();
+        IrisBiome surfaceBiome = caveDepthSurfaceBiome(x, z, naturalFallback);
-        IrisBiome surfaceBiome = naturalFallback || dimensionStackContext == null
+        int surfaceY = caveDepthSurfaceY(x, z, naturalFallback);
-                ? naturalFallback
+        return resolveDepthCaveBiome(x, y, z, surfaceBiome, surfaceY);
-                        ? getComplex().naturalSurfaceBiome(x, z)
+    }
-                        : getSurfaceBiome(x, z)
+
-                : getComplex().getTrueBiomeStream().get(x, z);
+    private IrisBiome caveDepthSurfaceBiome(int x, int z, boolean naturalFallback) {
-        int surfaceY = naturalFallback
+        if (naturalFallback) {
+            return getComplex().naturalSurfaceBiome(x, z);
+        }
+        return getDimensionStackContext() == null ? getSurfaceBiome(x, z) : getComplex().getTrueBiomeStream().get(x, z);
+    }
+
+    private int caveDepthSurfaceY(int x, int z, boolean naturalFallback) {
+        return naturalFallback
                 ? getComplex().naturalTrueHeight(x, z)
                 : getComplex().getHeightStream().get(x, z).intValue();
-        return resolveDepthCaveBiome(x, y, z, surfaceBiome, surfaceY);
     }
 
     @BlockCoordinates
@@ -431,7 +514,10 @@ public interface Engine extends DataProvider, Fallible, BlockUpdater, Renderer,
             IrisBiome surfaceBiome,
             int surfaceY
     ) {
-        IrisBiome caveBiome = getCaveBiome(x, z);
+        return depthCaveBiome(getCaveBiome(x, z), y, surfaceBiome, surfaceY);
+    }
+
+    private static IrisBiome depthCaveBiome(IrisBiome caveBiome, int y, IrisBiome surfaceBiome, int surfaceY) {
         if (caveBiome == null) {
             return surfaceBiome;
         }

core/src/main/java/art/arcane/iris/generation/runtime/IrisEngine.java

@@ -519,7 +519,7 @@ public class IrisEngine implements Engine {
                     return drawBiomeEnvironment(x, z, saved.get());
                 }
                 try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                             openGenerationHistoryCoordinateScopeUnchecked(x, z, "draw a pregeneration preview")) {
+                             openGenerationHistoryReadScope(x, z, "draw a pregeneration preview")) {
                     return Engine.super.draw(x, z);
                 }
             });
@@ -535,7 +535,7 @@ public class IrisEngine implements Engine {
             return saved.get();
         }
         try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                     openGenerationHistoryCoordinateScopeUnchecked(x, z, "resolve a biome environment")) {
+                     openGenerationHistoryReadScope(x, z, "resolve a biome environment")) {
             return Engine.super.getBiomeEnvironment(x, y, z);
         }
     }
@@ -547,7 +547,7 @@ public class IrisEngine implements Engine {
             return saved.get();
         }
         try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                     openGenerationHistoryCoordinateScopeUnchecked(x, z, "resolve a mantle biome environment")) {
+                     openGenerationHistoryReadScope(x, z, "resolve a mantle biome environment")) {
             return Engine.super.getBiomeOrMantleEnvironment(x, y, z);
         }
     }
@@ -559,7 +559,7 @@ public class IrisEngine implements Engine {
             return saved.get();
         }
         try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                     openGenerationHistoryCoordinateScopeUnchecked(x, z, "resolve a surface biome environment")) {
+                     openGenerationHistoryReadScope(x, z, "resolve a surface biome environment")) {
             return Engine.super.getSurfaceBiomeEnvironment(x, z);
         }
     }
@@ -595,7 +595,7 @@ public class IrisEngine implements Engine {
             return saved.get().biome();
         }
         try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                     openGenerationHistoryCoordinateScopeUnchecked(x, z, "resolve a biome")) {
+                     openGenerationHistoryReadScope(x, z, "resolve a biome")) {
             return Engine.super.getBiome(x, y, z);
         }
     }
@@ -608,11 +608,27 @@ public class IrisEngine implements Engine {
             return saved.get().biome();
         }
         try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                     openGenerationHistoryCoordinateScopeUnchecked(x, z, "resolve a biome or mantle biome")) {
+                     openGenerationHistoryReadScope(x, z, "resolve a biome or mantle biome")) {
             return Engine.super.getBiomeOrMantle(x, y, z);
         }
     }
 
+    @BlockCoordinates
+    @Override
+    public void getBiomeOrMantleColumn(int x, int z, int step, IrisBiome[] biomes, IrisRegion[] regions) {
+        if (usesSavedBiomeEnvironment()) {
+            for (int index = 0; index < biomes.length; index++) {
+                biomes[index] = getBiomeOrMantle(x, index * step, z);
+                regions[index] = getRegion(x, index * step, z);
+            }
+            return;
+        }
+        try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
+                     openGenerationHistoryReadScope(x, z, "resolve a biome or mantle biome column")) {
+            Engine.super.getBiomeOrMantleColumn(x, z, step, biomes, regions);
+        }
+    }
+
     @BlockCoordinates
     @Override
     public IrisRegion getRegion(int x, int z) {
@@ -621,7 +637,7 @@ public class IrisEngine implements Engine {
             return saved.get().region();
         }
         try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                     openGenerationHistoryCoordinateScopeUnchecked(x, z, "resolve a region")) {
+                     openGenerationHistoryReadScope(x, z, "resolve a region")) {
             return Engine.super.getRegion(x, z);
         }
     }
@@ -634,7 +650,7 @@ public class IrisEngine implements Engine {
             return saved.get().region();
         }
         try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                     openGenerationHistoryCoordinateScopeUnchecked(x, z, "resolve a vertical region")) {
+                     openGenerationHistoryReadScope(x, z, "resolve a vertical region")) {
             return Engine.super.getRegion(x, y, z);
         }
     }
@@ -647,7 +663,7 @@ public class IrisEngine implements Engine {
             return saved.get().biome();
         }
         try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                     openGenerationHistoryCoordinateScopeUnchecked(x, z, "resolve a cave or mantle biome")) {
+                     openGenerationHistoryReadScope(x, z, "resolve a cave or mantle biome")) {
             return Engine.super.getCaveOrMantleBiome(x, y, z);
         }
     }
@@ -665,7 +681,7 @@ public class IrisEngine implements Engine {
             return Engine.super.getCaveBiome(x, z);
         }
         try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                     openGenerationHistoryCoordinateScopeUnchecked(x, z, "resolve a cave biome")) {
+                     openGenerationHistoryReadScope(x, z, "resolve a cave biome")) {
             return Engine.super.getCaveBiome(x, z);
         }
     }
@@ -692,7 +708,7 @@ public class IrisEngine implements Engine {
             return Engine.super.getCaveBiome(x, y, z, state);
         }
         try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                     openGenerationHistoryCoordinateScopeUnchecked(x, z, "resolve a vertical cave biome")) {
+                     openGenerationHistoryReadScope(x, z, "resolve a vertical cave biome")) {
             return Engine.super.getCaveBiome(x, y, z, state);
         }
     }
@@ -708,7 +724,7 @@ public class IrisEngine implements Engine {
             return Engine.super.getSurfaceBiome(x, z);
         }
         try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                     openGenerationHistoryCoordinateScopeUnchecked(x, z, "resolve a surface biome")) {
+                     openGenerationHistoryReadScope(x, z, "resolve a surface biome")) {
             return Engine.super.getSurfaceBiome(x, z);
         }
     }
@@ -717,7 +733,7 @@ public class IrisEngine implements Engine {
     @Override
     public double getSlope(int x, int z) {
         try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                     openGenerationHistoryCoordinateScopeUnchecked(x, z, "resolve terrain slope")) {
+                     openGenerationHistoryReadScope(x, z, "resolve terrain slope")) {
             return Engine.super.getSlope(x, z);
         }
     }
@@ -732,7 +748,7 @@ public class IrisEngine implements Engine {
     @Override
     public int getHeight(int x, int z, boolean ignoreFluid) {
         try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                     openGenerationHistoryCoordinateScopeUnchecked(x, z, "resolve terrain height")) {
+                     openGenerationHistoryReadScope(x, z, "resolve terrain height")) {
             return Engine.super.getHeight(x, z, ignoreFluid);
         }
     }
@@ -745,7 +761,7 @@ public class IrisEngine implements Engine {
             return recorded.get().objectKeys();
         }
         try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                     openGenerationHistoryCoordinateScopeUnchecked(x << 4, z << 4, "resolve chunk objects")) {
+                     openGenerationHistoryReadScope(x << 4, z << 4, "resolve chunk objects")) {
             return getMantle().getObjectComponent().guess(x, z);
         }
     }
@@ -758,7 +774,7 @@ public class IrisEngine implements Engine {
             return new HashSet<>(recorded.get().pointsOfInterest());
         }
         try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                     openGenerationHistoryCoordinateScopeUnchecked(
+                     openGenerationHistoryReadScope(
                              chunkX << 4, chunkZ << 4, "resolve chunk points of interest")) {
             Set<ChunkGenerationSemantics.PointOfInterest> pois = new HashSet<>();
             getMantle().getMantle().iterateChunk(
@@ -854,7 +870,7 @@ public class IrisEngine implements Engine {
                 int queryMinimumZ = Math.max(minimumZ, chunkMinimumZ);
                 int queryMaximumZ = Math.min(maximumZ, chunkMinimumZ + 15);
                 try (GenerationHistoryRuntimeRouter.CoordinateScope ignored =
-                             openGenerationHistoryCoordinateScopeUnchecked(
+                             openGenerationHistoryReadScope(
                                      chunkMinimumX,
                                      chunkMinimumZ,
                                      "resolve native structure volumes")) {
@@ -981,13 +997,16 @@ public class IrisEngine implements Engine {
         return hasGenerationRuntimeScope() && getComplex().isNaturalTerrainContext();
     }
 
-    private GenerationHistoryRuntimeRouter.CoordinateScope openGenerationHistoryCoordinateScopeUnchecked(
+    private GenerationHistoryRuntimeRouter.CoordinateScope openGenerationHistoryReadScope(
             int blockX,
             int blockZ,
             String operation
     ) {
         try {
-            return openGenerationHistoryCoordinateScope(blockX, blockZ);
+            GenerationHistoryRuntimeRouter router = generationHistoryRuntimeRouter;
+            return router == null
+                    ? openGenerationHistoryCoordinateScope(blockX, blockZ)
+                    : router.openReadScope(blockX, blockZ);
         } catch (IOException failure) {
             throw new IllegalStateException("Unable to " + operation + " through Iris generation history at "
                     + blockX + "," + blockZ + ".", failure);

core/src/main/java/art/arcane/iris/generation/stage/IrisTransitionGeometryActuator.java

@@ -95,6 +95,9 @@ public final class IrisTransitionGeometryActuator extends EngineAssignedComponen
         private final int minimumY;
         private final ChunkContext context;
         private final Map<NativeBlockState, BoundaryColumnGeometry.Voxel> voxels = new IdentityHashMap<>();
+        private NativeBlockState air;
+        private NativeBlockState lastState;
+        private BoundaryColumnGeometry.Voxel lastVoxel;
 
         private GeometrySource(Hunk<NativeBlockState> blocks, Hunk<NativeBiome> biomes, int minimumY, ChunkContext context) {
             this.blocks = blocks;
@@ -107,9 +110,16 @@ public final class IrisTransitionGeometryActuator extends EngineAssignedComponen
         public BoundaryColumnGeometry.Voxel voxel(int localX, int worldY, int localZ) {
             NativeBlockState state = blocks.getRaw(localX, worldY - minimumY, localZ);
             if (state == null) {
-                state = IrisPlatforms.get().registries().air();
+                if (air == null) {
+                    air = IrisPlatforms.get().registries().air();
+                }
+                state = air;
             }
-            return voxels.computeIfAbsent(state, GeometrySource::encode);
+            if (state != lastState) {
+                lastVoxel = voxels.computeIfAbsent(state, GeometrySource::encode);
+                lastState = state;
+            }
+            return lastVoxel;
         }
 
         @Override

core/src/main/java/art/arcane/iris/generation/terrain/IrisDimensionCarvingResolver.java

@@ -14,7 +14,7 @@ import art.arcane.volmlib.util.noise.CNG;
 
 import java.lang.ref.WeakReference;
 import java.util.ArrayList;
-import java.util.HashMap;
+import java.util.Arrays;
 import java.util.IdentityHashMap;
 import java.util.List;
 import java.util.Map;
@@ -81,8 +81,9 @@ public final class IrisDimensionCarvingResolver {
     }
 
     private static IrisDimensionCarvingEntry resolveBoundRootEntry(Engine engine, int worldY, IrisData data, State resolvedState) {
-        if (resolvedState.rootEntriesByWorldY.containsKey(worldY)) {
+        int slot = resolvedState.rootSlot(worldY);
-            return resolvedState.rootEntriesByWorldY.get(worldY);
+        if (slot >= 0) {
+            return resolvedState.roots[slot];
         }
 
         return selectBoundRootEntry(engine.getDimension(), worldY, data, resolvedState);
@@ -91,7 +92,7 @@ public final class IrisDimensionCarvingResolver {
     private static IrisDimensionCarvingEntry selectBoundRootEntry(IrisDimension dimension, int worldY, IrisData data, State resolvedState) {
         List<IrisDimensionCarvingEntry> entries = dimension.getCarving();
         if (entries == null || entries.isEmpty()) {
-            resolvedState.rootEntriesByWorldY.put(worldY, null);
+            resolvedState.rememberRoot(worldY, null);
             return null;
         }
 
@@ -104,7 +105,7 @@ public final class IrisDimensionCarvingResolver {
             resolved = entry;
         }
 
-        resolvedState.rootEntriesByWorldY.put(worldY, resolved);
+        resolvedState.rememberRoot(worldY, resolved);
         return resolved;
     }
 
@@ -324,8 +325,9 @@ public final class IrisDimensionCarvingResolver {
         }
 
         public IrisBiome resolveBiome(int worldX, int worldY, int worldZ) {
-            IrisDimensionCarvingEntry root = state.rootEntriesByWorldY.containsKey(worldY)
+            int slot = state.rootSlot(worldY);
-                    ? state.rootEntriesByWorldY.get(worldY)
+            IrisDimensionCarvingEntry root = slot >= 0
+                    ? state.roots[slot]
                     : selectBoundRootEntry(dimension, worldY, data, state);
             if (root == null) {
                 return null;
@@ -336,7 +338,11 @@ public final class IrisDimensionCarvingResolver {
     }
 
     public static final class State {
-        private final Map<Integer, IrisDimensionCarvingEntry> rootEntriesByWorldY = new HashMap<>();
+        private static final int ROOT_SLOTS = 512;
+
+        private int[] rootWorldYs;
+        private IrisDimensionCarvingEntry[] roots;
+        private boolean[] rootsKnown;
         private final Map<IrisDimensionCarvingEntry, IrisRaritySelection<CarvingChoice>> selectionPlans = new IdentityHashMap<>();
         private final Map<IrisDimensionCarvingEntry, IrisBiome> biomeCache = new IdentityHashMap<>();
         private WeakReference<Engine> engineIdentity;
@@ -357,7 +363,10 @@ public final class IrisDimensionCarvingResolver {
             engineIdentity = new WeakReference<>(engine);
             dimensionIdentity = new WeakReference<>(dimension);
             dataIdentity = new WeakReference<>(data);
-            rootEntriesByWorldY.clear();
+            if (rootsKnown != null) {
+                Arrays.fill(rootsKnown, false);
+                Arrays.fill(roots, null);
+            }
             selectionPlans.clear();
             biomeCache.clear();
             entryIndex = null;
@@ -366,6 +375,23 @@ public final class IrisDimensionCarvingResolver {
             return data;
         }
 
+        private int rootSlot(int worldY) {
+            int slot = worldY & (ROOT_SLOTS - 1);
+            return rootsKnown != null && rootsKnown[slot] && rootWorldYs[slot] == worldY ? slot : -1;
+        }
+
+        private void rememberRoot(int worldY, IrisDimensionCarvingEntry root) {
+            if (rootsKnown == null) {
+                rootWorldYs = new int[ROOT_SLOTS];
+                roots = new IrisDimensionCarvingEntry[ROOT_SLOTS];
+                rootsKnown = new boolean[ROOT_SLOTS];
+            }
+            int slot = worldY & (ROOT_SLOTS - 1);
+            rootWorldYs[slot] = worldY;
+            roots[slot] = root;
+            rootsKnown[slot] = true;
+        }
+
         private static boolean references(WeakReference<?> identity, Object value) {
             return identity != null && identity.get() == value;
         }

core/src/main/java/art/arcane/iris/world/history/BoundaryColumnGeometry.java

@@ -9,14 +9,10 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
-import java.util.TreeSet;
 
 public final class BoundaryColumnGeometry implements NativeBlockColumn {
     public static final int MAXIMUM_HEIGHT = 65_536;
-    private static final Comparator<Voxel> VOXEL_ORDER = Comparator.comparing(Voxel::stateKey)
+    private static final Comparator<Voxel> VOXEL_ORDER = BoundaryColumnGeometry::compareVoxels;
-            .thenComparing(Voxel::phase)
-            .thenComparing(Voxel::fluidStateKey)
-            .thenComparing(Voxel::protectedContent);
     private static final Voxel AIR = new Voxel("minecraft:air", Phase.AIR, "", false);
     private static final BoundaryColumnGeometry EMPTY = new BoundaryColumnGeometry(0, List.of(), new int[0], new short[0]);
 
@@ -42,36 +38,24 @@ public final class BoundaryColumnGeometry implements NativeBlockColumn {
         if (voxels.size() > MAXIMUM_HEIGHT) {
             throw new IllegalArgumentException("Geometry column exceeds maximum height");
         }
-        TreeSet<Voxel> used = new TreeSet<>(VOXEL_ORDER);
+        Runs runs = new Runs(voxels.size());
-        Voxel previous = null;
         for (Voxel voxel : voxels) {
-            if (previous == null || !previous.equals(voxel)) {
+            runs.add(voxel);
-                used.add(voxel);
-                previous = voxel;
-            }
         }
-        List<Voxel> palette = List.copyOf(used);
+        return runs.build(minimumY);
-        Map<Voxel, Short> indices = new HashMap<>(palette.size());
+    }
-        for (int index = 0; index < palette.size(); index++) {
+
-            if (index > Short.MAX_VALUE) {
+    private static int compareVoxels(Voxel first, Voxel second) {
-                throw new IllegalArgumentException("Geometry palette exceeds compact index capacity");
+        int order = first.stateKey().compareTo(second.stateKey());
-            }
+        if (order != 0) {
-            indices.put(palette.get(index), (short) index);
+            return order;
         }
-        int[] ends = new int[voxels.size()];
+        order = first.phase().compareTo(second.phase());
-        short[] values = new short[voxels.size()];
+        if (order != 0) {
-        int runCount = 0;
+            return order;
-        previous = null;
-        for (int offset = 0; offset < voxels.size(); offset++) {
-            Voxel voxel = voxels.get(offset);
-            if (previous == null || !previous.equals(voxel)) {
-                values[runCount++] = indices.get(voxel);
-                previous = voxel;
-            }
-            ends[runCount - 1] = offset + 1;
         }
-        return new BoundaryColumnGeometry(minimumY, palette,
+        order = first.fluidStateKey().compareTo(second.fluidStateKey());
-                Arrays.copyOf(ends, runCount), Arrays.copyOf(values, runCount));
+        return order != 0 ? order : Boolean.compare(first.protectedContent(), second.protectedContent());
     }
 
     public int minimumY() {
@@ -256,6 +240,90 @@ public final class BoundaryColumnGeometry implements NativeBlockColumn {
         }
     }
 
+    static final class Runs {
+        private static final int LINEAR_PALETTE_LIMIT = 32;
+
+        private final Voxel[] voxels;
+        private final int[] ends;
+        private int count;
+        private int length;
+
+        Runs(int capacity) {
+            voxels = new Voxel[capacity];
+            ends = new int[capacity];
+        }
+
+        void clear() {
+            count = 0;
+            length = 0;
+        }
+
+        void add(Voxel voxel) {
+            Objects.requireNonNull(voxel, "Geometry voxel");
+            if (count == 0 || !sameVoxel(voxels[count - 1], voxel)) {
+                voxels[count++] = voxel;
+            }
+            ends[count - 1] = ++length;
+        }
+
+        BoundaryColumnGeometry build(int minimumY) {
+            Voxel[] distinct = new Voxel[count];
+            int[] slots = new int[count];
+            Map<Voxel, Integer> lookup = null;
+            int distinctCount = 0;
+            for (int run = 0; run < count; run++) {
+                Voxel voxel = voxels[run];
+                int slot = lookup == null ? linearIndex(distinct, distinctCount, voxel) : lookup.getOrDefault(voxel, -1);
+                if (slot < 0) {
+                    slot = distinctCount;
+                    distinct[distinctCount++] = voxel;
+                    if (lookup != null) {
+                        lookup.put(voxel, slot);
+                    } else if (distinctCount > LINEAR_PALETTE_LIMIT) {
+                        lookup = new HashMap<>();
+                        for (int index = 0; index < distinctCount; index++) {
+                            lookup.put(distinct[index], index);
+                        }
+                    }
+                }
+                slots[run] = slot;
+            }
+            if (distinctCount > Short.MAX_VALUE + 1) {
+                throw new IllegalArgumentException("Geometry palette exceeds compact index capacity");
+            }
+            Voxel[] palette = Arrays.copyOf(distinct, distinctCount);
+            Arrays.sort(palette, VOXEL_ORDER);
+            short[] slotIndices = new short[distinctCount];
+            if (lookup == null) {
+                for (int slot = 0; slot < distinctCount; slot++) {
+                    slotIndices[slot] = (short) linearIndex(palette, distinctCount, distinct[slot]);
+                }
+            } else {
+                for (int index = 0; index < distinctCount; index++) {
+                    slotIndices[lookup.get(palette[index])] = (short) index;
+                }
+            }
+            short[] values = new short[count];
+            for (int run = 0; run < count; run++) {
+                values[run] = slotIndices[slots[run]];
+            }
+            return new BoundaryColumnGeometry(minimumY, Arrays.asList(palette), Arrays.copyOf(ends, count), values);
+        }
+
+        private static int linearIndex(Voxel[] values, int size, Voxel voxel) {
+            for (int index = 0; index < size; index++) {
+                if (sameVoxel(values[index], voxel)) {
+                    return index;
+                }
+            }
+            return -1;
+        }
+
+        private static boolean sameVoxel(Voxel first, Voxel second) {
+            return first == second || first.equals(second);
+        }
+    }
+
     public enum Phase {
         AIR,
         SOLID,

core/src/main/java/art/arcane/iris/world/history/GenerationHistoryRuntimeRouter.java

@@ -391,6 +391,25 @@ public final class GenerationHistoryRuntimeRouter implements AutoCloseable {
         return new CoordinateScope(blockX, blockZ, stage.route, stage);
     }
 
+    /**
+     * A coordinate scope for engine reads. Inside another chunk's route whose runtime the thread is bound to, it borrows
+     * that runtime instead of opening a stage: every generation stage binds the active activation, which cannot change
+     * while the route holds its transition participation.
+     */
+    public CoordinateScope openReadScope(int blockX, int blockZ) throws IOException {
+        RuntimeRoute current = scopedRoute.get();
+        if (current != null) {
+            if (current.chunkX() == Math.floorDiv(blockX, GenerationBoundary.CHUNK_SIZE)
+                    && current.chunkZ() == Math.floorDiv(blockZ, GenerationBoundary.CHUNK_SIZE)) {
+                return new CoordinateScope(blockX, blockZ, current, null);
+            }
+            if (current.binding == engine.captureGenerationRuntimeBinding()) {
+                return new CoordinateScope(blockX, blockZ, null, null);
+            }
+        }
+        return openCoordinateScope(blockX, blockZ);
+    }
+
     public void recordNaturalTerrain(SavedTerrainChunk terrain) {
         SavedTerrainChunk captured = Objects.requireNonNull(terrain, "natural terrain");
         RuntimeRoute route = scopedRoute.get();

core/src/main/java/art/arcane/iris/world/history/GenerationSemanticCapture.java

@@ -227,12 +227,12 @@ public final class GenerationSemanticCapture {
         }
         resolvedCaves.set(position);
         if (explicitBiomeKey != null && !explicitBiomeKey.isBlank()) {
-            semantics.addCaveBiome(explicitBiomeKey);
+            caveBiomes.add(semantics, explicitBiomeKey);
             return;
         }
         IrisBiome caveBiome = caveBiomes.resolve(blockX, y, blockZ);
         if (caveBiome != null && caveBiome.getLoadKey() != null) {
-            semantics.addCaveBiome(caveBiome.getLoadKey());
+            caveBiomes.add(semantics, caveBiome.getLoadKey());
         }
     }
 
@@ -280,6 +280,7 @@ public final class GenerationSemanticCapture {
         private final IrisDimensionCarvingResolver.State fallbackState = new IrisDimensionCarvingResolver.State();
         private IrisDimensionCarvingResolver.Snapshot snapshot;
         private int minimumY;
+        private String lastKey;
 
         private CaveBiomes(Engine engine, boolean scoped) {
             this.engine = engine;
@@ -290,6 +291,13 @@ public final class GenerationSemanticCapture {
                     : null;
         }
 
+        private void add(ChunkGenerationSemantics.Builder semantics, String key) {
+            if (key != lastKey) {
+                semantics.addCaveBiome(key);
+                lastKey = key;
+            }
+        }
+
         private IrisBiome resolve(int x, int y, int z) {
             if (!scoped) {
                 return engine.getCaveBiome(x, y, z);

core/src/main/java/art/arcane/iris/world/history/GenerationSemanticIndex.java

@@ -1075,7 +1075,11 @@ public final class GenerationSemanticIndex {
 
     private void cacheRegion(long regionKey, RegionShard region) {
         regions.put(regionKey, region);
-        cacheSummary(regionKey, region.summary());
+        if (region.summary == null) {
+            summaries.remove(regionKey);
+        } else {
+            cacheSummary(regionKey, region.summary);
+        }
         while (regions.size() > MAXIMUM_CACHED_REGIONS) {
             Iterator<Map.Entry<Long, RegionShard>> entries = regions.entrySet().iterator();
             entries.next();

core/src/main/java/art/arcane/iris/world/history/SavedBiomeCapture.java

@@ -6,6 +6,7 @@ import art.arcane.iris.generation.terrain.IrisRegion;
 
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -30,6 +31,8 @@ public final class SavedBiomeCapture {
         TransitionGenerationPlan transition = engine.getComplex().getTransitionGenerationPlan();
         Map<Long, Optional<SavedBiomeChunk>> historical = new HashMap<>();
         Map<Integer, List<SavedBiomeChunk.Span>> vertical = new HashMap<>(16);
+        Cells cells = new Cells(activationId);
+        Column column = new Column(engine, minimumY, height);
         for (int localX = 0; localX < 16; localX++) {
             for (int localZ = 0; localZ < 16; localZ++) {
                 int blockX = startX + localX;
@@ -37,7 +40,7 @@ public final class SavedBiomeCapture {
                 IrisRegion region = engine.getRegion(blockX, blockZ);
                 IrisBiome surface = engine.getSurfaceBiome(blockX, blockZ);
                 int surfaceY = minimumY + engine.getHeight(blockX, blockZ);
-                SavedBiomeChunk.Cell surfaceCell = cell(activationId, surface, region);
+                SavedBiomeChunk.Cell surfaceCell = cells.cell(surface, region);
                 if (floating != null) {
                     FloatingBiomeOverlay.Identity floatingSurface = floating.surfaceAt(localX, localZ);
                     if (floatingSurface != null) {
@@ -53,33 +56,33 @@ public final class SavedBiomeCapture {
                 int quartKey = quartX * 16 + quartZ;
                 List<SavedBiomeChunk.Span> spans = vertical.get(quartKey);
                 if (spans == null) {
-                    spans = captureVertical(new Column(engine, activationId, startX + quartX, startZ + quartZ), transition, saved, historical, floating);
+                    spans = captureVertical(column, startX + quartX, startZ + quartZ, cells, transition, saved, historical, floating);
                     vertical.put(quartKey, spans);
                 }
-                SavedBiomeChunk.Cell caveBase = cell(activationId, engine.getCaveBiome(blockX, blockZ), region);
+                SavedBiomeChunk.Cell caveBase = cells.cell(engine.getCaveBiome(blockX, blockZ), region);
                 result.column(localX, localZ, new SavedBiomeChunk.Column(surfaceCell, caveBase, spans));
             }
         }
         return result.build();
     }
 
-    private static List<SavedBiomeChunk.Span> captureVertical(Column column, TransitionGenerationPlan transition,
+    private static List<SavedBiomeChunk.Span> captureVertical(Column column, int blockX, int blockZ, Cells cells,
-                                                             SavedBiomeRuntime saved, Map<Long, Optional<SavedBiomeChunk>> historical, FloatingBiomeOverlay floating) throws IOException {
+                                                             TransitionGenerationPlan transition, SavedBiomeRuntime saved,
-        Engine engine = column.engine();
+                                                             Map<Long, Optional<SavedBiomeChunk>> historical, FloatingBiomeOverlay floating) throws IOException {
-        int minimumY = engine.getMinHeight();
+        column.engine().getBiomeOrMantleColumn(blockX, blockZ, 4, column.biomes(), column.regions());
-        int maximumY = minimumY + engine.getHeight();
+        int minimumY = column.minimumY();
+        int maximumY = minimumY + column.height();
         List<SavedBiomeChunk.Span> spans = new ArrayList<>();
         SavedBiomeChunk.Cell previous = null;
         int startY = minimumY;
-        for (int worldY = minimumY; worldY < maximumY; worldY += 4) {
+        for (int index = 0; index < column.biomes().length; index++) {
-            IrisBiome biome = engine.getBiomeOrMantle(column.blockX(), worldY - minimumY, column.blockZ());
+            int worldY = minimumY + index * 4;
-            IrisRegion region = engine.getRegion(column.blockX(), worldY - minimumY, column.blockZ());
+            SavedBiomeChunk.Cell current = cells.cell(column.biomes()[index], column.regions()[index]);
-            SavedBiomeChunk.Cell current = cell(column.activationId(), biome, region);
             if (floating != null) {
-                current = overlay(current, floating.volumeAt(column.blockX() & 15, worldY - minimumY, column.blockZ() & 15));
+                current = overlay(current, floating.volumeAt(blockX & 15, worldY - minimumY, blockZ & 15));
             }
             if (transition != null) {
-                current = historicalCell(new Sample(column.blockX(), worldY, column.blockZ(), false), current, transition, saved, historical);
+                current = historicalCell(new Sample(blockX, worldY, blockZ, false), current, transition, saved, historical);
             }
             if (previous != null && !previous.equals(current)) {
                 spans.add(new SavedBiomeChunk.Span(startY, worldY, previous));
@@ -132,7 +135,40 @@ public final class SavedBiomeCapture {
                 Objects.requireNonNull(region, "region").getLoadKey());
     }
 
-    private record Column(Engine engine, long activationId, int blockX, int blockZ) {
+    private record Column(Engine engine, int minimumY, int height, IrisBiome[] biomes, IrisRegion[] regions) {
+        private Column(Engine engine, int minimumY, int height) {
+            this(engine, minimumY, height, new IrisBiome[(height + 3) / 4], new IrisRegion[(height + 3) / 4]);
+        }
+    }
+
+    private static final class Cells {
+        private final long activationId;
+        private IrisBiome[] biomes = new IrisBiome[8];
+        private IrisRegion[] regions = new IrisRegion[8];
+        private SavedBiomeChunk.Cell[] cells = new SavedBiomeChunk.Cell[8];
+        private int size;
+
+        private Cells(long activationId) {
+            this.activationId = activationId;
+        }
+
+        private SavedBiomeChunk.Cell cell(IrisBiome biome, IrisRegion region) {
+            for (int index = 0; index < size; index++) {
+                if (biomes[index] == biome && regions[index] == region) {
+                    return cells[index];
+                }
+            }
+            SavedBiomeChunk.Cell created = SavedBiomeCapture.cell(activationId, biome, region);
+            if (size == cells.length) {
+                biomes = Arrays.copyOf(biomes, size * 2);
+                regions = Arrays.copyOf(regions, size * 2);
+                cells = Arrays.copyOf(cells, size * 2);
+            }
+            biomes[size] = biome;
+            regions[size] = region;
+            cells[size++] = created;
+            return created;
+        }
     }
 
     private record Sample(int x, int y, int z, boolean surface) {

core/src/main/java/art/arcane/iris/world/history/SavedTerrainChunk.java

@@ -4,9 +4,7 @@ import java.io.IOException;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Collections;
-import java.util.LinkedHashMap;
 import java.util.List;
-import java.util.Map;
 import java.util.Objects;
 import java.util.OptionalInt;
 
@@ -65,14 +63,15 @@ public final class SavedTerrainChunk {
         }
         Math.addExact(minimumY, height);
         List<TerrainBoundarySignature> columns = new ArrayList<>(256);
+        BoundaryColumnGeometry.Runs runs = new BoundaryColumnGeometry.Runs(height);
         for (int x = 0; x < 16; x++) {
             for (int z = 0; z < 16; z++) {
                 if (boundaryOnly && x != 0 && x != 15 && z != 0 && z != 15) {
                     columns.add(null);
                     continue;
                 }
-                List<BoundaryColumnGeometry.Voxel> voxels = new ArrayList<>(height);
+                runs.clear();
-                Map<String, Short> biomePalette = new LinkedHashMap<>();
+                List<String> biomePalette = new ArrayList<>(4);
                 short[] biomeIndices = new short[height / 4];
                 int surface = 0;
                 int floor = 0;
@@ -80,7 +79,7 @@ public final class SavedTerrainChunk {
                 for (int offset = 0; offset < height; offset++) {
                     int y = minimumY + offset;
                     BoundaryColumnGeometry.Voxel voxel = Objects.requireNonNull(source.voxel(x, y, z), "voxel");
-                    voxels.add(voxel);
+                    runs.add(voxel);
                     if (voxel.phase() != BoundaryColumnGeometry.Phase.AIR) {
                         surface = offset;
                     }
@@ -92,15 +91,10 @@ public final class SavedTerrainChunk {
                     }
                     if (offset % 4 == 0) {
                         String biome = Objects.requireNonNull(source.biome(x, y, z), "physical biome");
-                        Short index = biomePalette.get(biome);
+                        biomeIndices[offset / 4] = paletteIndex(biomePalette, biome);
-                        if (index == null) {
-                            index = (short) biomePalette.size();
-                            biomePalette.put(biome, index);
-                        }
-                        biomeIndices[offset / 4] = index;
                     }
                 }
-                BoundaryColumnGeometry geometry = BoundaryColumnGeometry.fromVoxels(minimumY, voxels);
+                BoundaryColumnGeometry geometry = runs.build(minimumY);
                 OptionalInt groundSurface = source.groundSurface(x, z);
                 if (groundSurface.isPresent()) {
                     floor = geometry.surfaceOffsetNear(groundSurface.getAsInt());
@@ -115,13 +109,24 @@ public final class SavedTerrainChunk {
                                 fluid > floor ? OptionalInt.of(fluid) : OptionalInt.empty(), OptionalInt.empty()),
                         new TerrainBoundarySignature.Samples(
                                 new TerrainBoundarySignature.VerticalLayout(minimumY, 4, biomeIndices.length),
-                                new TerrainBoundarySignature.BiomeEncoding(List.copyOf(biomePalette.keySet()), biomeIndices)),
+                                new TerrainBoundarySignature.BiomeEncoding(biomePalette, biomeIndices)),
                         geometry));
             }
         }
         return new SavedTerrainChunk(chunkX, chunkZ, nativeStatus, columns);
     }
 
+    private static short paletteIndex(List<String> palette, String biome) {
+        for (int index = 0; index < palette.size(); index++) {
+            String candidate = palette.get(index);
+            if (candidate == biome || candidate.equals(biome)) {
+                return (short) index;
+            }
+        }
+        palette.add(biome);
+        return (short) (palette.size() - 1);
+    }
+
     public SavedTerrainChunk boundaryOnly() {
         if (!hasColumn(1, 1)) {
             return this;

core/src/test/java/art/arcane/iris/generation/runtime/EngineBiomeColumnTest.java

@@ -0,0 +1,180 @@
+package art.arcane.iris.generation.runtime;
+
+import art.arcane.iris.generation.biome.IrisBiome;
+import art.arcane.iris.generation.block.B;
+import art.arcane.iris.generation.mantle.EngineMantle;
+import art.arcane.iris.generation.terrain.IrisDimension;
+import art.arcane.iris.generation.terrain.IrisDimensionCarvingEntry;
+import art.arcane.iris.generation.terrain.IrisRegion;
+import art.arcane.iris.pack.loading.IrisData;
+import art.arcane.iris.pack.loading.ResourceLoader;
+import art.arcane.iris.pack.value.IrisRange;
+import art.arcane.iris.world.IrisWorld;
+import art.arcane.volmlib.nativelib.terrain.NativeBlockState;
+import art.arcane.volmlib.util.collection.KList;
+import art.arcane.volmlib.util.collection.KMap;
+import art.arcane.volmlib.util.mantle.runtime.Mantle;
+import art.arcane.volmlib.util.mantle.runtime.MantleChunk;
+import art.arcane.volmlib.util.matter.Matter;
+import art.arcane.volmlib.util.matter.MatterCavern;
+import art.arcane.volmlib.util.stream.ProceduralStream;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.mockito.MockedStatic;
+
+import java.util.List;
+import java.util.Random;
+
+import static org.junit.Assert.assertSame;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyBoolean;
+import static org.mockito.ArgumentMatchers.anyDouble;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.CALLS_REAL_METHODS;
+import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.when;
+
+public class EngineBiomeColumnTest {
+    private static final int SAMPLES = 96;
+
+    @BeforeClass
+    public static void initializeMantleBlockState() throws Exception {
+        NativeBlockState air = mock(NativeBlockState.class);
+        try (MockedStatic<B> blocks = mockStatic(B.class)) {
+            blocks.when(() -> B.getState("AIR")).thenReturn(air);
+            Class.forName(EngineMantle.class.getName());
+        }
+    }
+
+    @Test
+    public void columnMatchesPointLookupsAcrossCavesSurfacesAndMantleBiomes() {
+        Random random = new Random(1337L);
+        for (int trial = 0; trial < 48; trial++) {
+            Engine engine = randomEngine(random, trial);
+            for (int column = 0; column < 24; column++) {
+                int x = random.nextInt(4096) - 2048;
+                int z = random.nextInt(4096) - 2048;
+                IrisBiome[] biomes = new IrisBiome[SAMPLES];
+                IrisRegion[] regions = new IrisRegion[SAMPLES];
+                engine.getBiomeOrMantleColumn(x, z, 4, biomes, regions);
+                for (int index = 0; index < SAMPLES; index++) {
+                    assertSame(engine.getBiomeOrMantle(x, index * 4, z), biomes[index]);
+                    assertSame(engine.getRegion(x, index * 4, z), regions[index]);
+                }
+            }
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    private static Engine randomEngine(Random random, int trial) {
+        long salt = random.nextLong();
+        IrisBiome[] surfaces = {biome("iris:plains", 0), biome("iris:desert", 0), biome("iris:forest", 0)};
+        IrisBiome[] caves = {biome("iris:lush_caves", 0), biome("iris:deep_dark", 24), new IrisBiome(), null};
+        IrisRegion[] regions = {region("iris:temperate"), region("iris:arid")};
+        IrisBiome custom = biome("iris:custom_cave", 0);
+        IrisBiome configured = biome("iris:configured_cave", 0);
+
+        ProceduralStream<IrisBiome> surfaceStream = mock(ProceduralStream.class);
+        when(surfaceStream.get(anyDouble(), anyDouble())).thenAnswer(call ->
+                surfaces[pick(salt, call.getArgument(0), call.getArgument(1), 1, surfaces.length)]);
+        ProceduralStream<IrisBiome> caveStream = mock(ProceduralStream.class);
+        when(caveStream.get(anyDouble(), anyDouble())).thenAnswer(call ->
+                caves[pick(salt, call.getArgument(0), call.getArgument(1), 2, caves.length)]);
+        ProceduralStream<IrisRegion> regionStream = mock(ProceduralStream.class);
+        when(regionStream.get(anyDouble(), anyDouble())).thenAnswer(call ->
+                regions[pick(salt, call.getArgument(0), call.getArgument(1), 3, regions.length)]);
+        ProceduralStream<Double> heightStream = mock(ProceduralStream.class);
+        when(heightStream.get(anyDouble(), anyDouble())).thenAnswer(call ->
+                (double) (40 + pick(salt, call.getArgument(0), call.getArgument(1), 4, 300)));
+
+        IrisComplex complex = mock(IrisComplex.class);
+        when(complex.getTrueBiomeStream()).thenReturn(surfaceStream);
+        when(complex.getCaveBiomeStream()).thenReturn(caveStream);
+        when(complex.getRegionStream()).thenReturn(regionStream);
+        when(complex.getHeightStream()).thenReturn(heightStream);
+        when(complex.isTerrain3DSurface(anyInt(), anyInt(), anyInt())).thenAnswer(call ->
+                pick(salt, (int) call.getArgument(0) * 31 + (int) call.getArgument(1), (int) call.getArgument(2), 5, 9) == 0);
+
+        Mantle<Matter> mantle = mock(Mantle.class);
+        when(mantle.getWorldHeight()).thenReturn(384);
+        when(mantle.getLoadedRegions()).thenReturn(new KMap<>());
+        when(mantle.hasTectonicPlate(anyInt(), anyInt())).thenReturn(true);
+        when(mantle.get(anyInt(), anyInt(), anyInt(), eq(MatterCavern.class))).thenAnswer(call ->
+                cavern(salt, call.getArgument(0), call.getArgument(1), call.getArgument(2)));
+        when(mantle.getChunk(anyInt(), anyInt())).thenAnswer(call -> {
+            int chunkX = call.getArgument(0);
+            int chunkZ = call.getArgument(1);
+            MantleChunk<Matter> chunk = mock(MantleChunk.class);
+            when(chunk.use()).thenReturn(chunk);
+            when(chunk.get(anyInt(), anyInt(), anyInt(), eq(MatterCavern.class))).thenAnswer(read -> cavern(salt,
+                    chunkX * 16 + (int) read.getArgument(0), read.getArgument(1), chunkZ * 16 + (int) read.getArgument(2)));
+            return chunk;
+        });
+        EngineMantle engineMantle = mock(EngineMantle.class);
+        when(engineMantle.getMantle()).thenReturn(mantle);
+        doAnswer(call -> 20 + pick(salt, (int) call.getArgument(0), (int) call.getArgument(1), 7, 330))
+                .when(engineMantle).getHighest(anyInt(), anyInt(), any(IrisData.class), anyBoolean());
+
+        IrisData data = mock(IrisData.class);
+        ResourceLoader<IrisBiome> loader = mock(ResourceLoader.class);
+        when(data.getBiomeLoader()).thenReturn(loader);
+        when(loader.load(anyString())).thenReturn(null);
+        when(loader.load("iris:custom_cave")).thenReturn(custom);
+        when(loader.load("iris:configured_cave")).thenReturn(configured);
+
+        IrisDimension dimension = new IrisDimension();
+        if (trial % 2 == 1) {
+            IrisDimensionCarvingEntry root = new IrisDimensionCarvingEntry();
+            root.setBiome("iris:configured_cave");
+            int bottom = -64 + random.nextInt(120);
+            root.setWorldYRange(new IrisRange(bottom, bottom + 8 + random.nextInt(80)));
+            root.setChildRecursionDepth(0);
+            dimension.setCarving(new KList<>(List.of(root)));
+        }
+
+        EnginePlatformHooks hooks = mock(EnginePlatformHooks.class);
+        Engine engine = mock(Engine.class, CALLS_REAL_METHODS);
+        doReturn(complex).when(engine).getComplex();
+        doReturn(engineMantle).when(engine).getMantle();
+        doReturn(hooks).when(engine).getPlatformHooks();
+        doReturn(data).when(engine).getData();
+        doReturn(dimension).when(engine).getDimension();
+        doReturn(IrisWorld.builder().minHeight(-64).maxHeight(320).build()).when(engine).getWorld();
+        return engine;
+    }
+
+    private static MatterCavern cavern(long salt, int x, int y, int z) {
+        return switch (pick(salt, x * 17 + y, z, 6, 12)) {
+            case 0 -> new MatterCavern(true, "iris:custom_cave", (byte) 0);
+            case 1 -> new MatterCavern(true, "iris:missing_cave", (byte) 1);
+            case 2 -> new MatterCavern(true, "", (byte) 0);
+            default -> null;
+        };
+    }
+
+    private static int pick(long salt, double x, double z, int channel, int bound) {
+        long mixed = salt ^ ((long) x * 0x9E3779B97F4A7C15L) ^ ((long) z * 0xC2B2AE3D27D4EB4FL) ^ channel * 0x165667B19E3779F9L;
+        mixed ^= mixed >>> 33;
+        mixed *= 0xFF51AFD7ED558CCDL;
+        mixed ^= mixed >>> 33;
+        return (int) Math.floorMod(mixed, (long) bound);
+    }
+
+    private static IrisBiome biome(String key, int caveMinDepth) {
+        IrisBiome biome = new IrisBiome();
+        biome.setLoadKey(key);
+        biome.setCaveMinDepthBelowSurface(caveMinDepth);
+        return biome;
+    }
+
+    private static IrisRegion region(String key) {
+        IrisRegion region = new IrisRegion();
+        region.setLoadKey(key);
+        return region;
+    }
+}

core/src/test/java/art/arcane/iris/generation/runtime/IrisEngineGenerationRuntimeScopeTest.java

@@ -204,10 +204,10 @@ public class IrisEngineGenerationRuntimeScopeTest {
             assertSame(cave, engine.getCaveBiome(19, 20, -3, new IrisDimensionCarvingResolver.State()));
             assertSame(surface, engine.getSurfaceBiome(19, -3));
             assertSame(selected.complex, engine.getComplex());
-            verify(router, never()).openCoordinateScope(anyInt(), anyInt());
+            verify(router, never()).openReadScope(anyInt(), anyInt());
             when(context.isNaturalTerrain()).thenReturn(false);
             assertSame(cave, engine.getCaveBiome(19, -3));
-            verify(router, times(1)).openCoordinateScope(19, -3);
+            verify(router, times(1)).openReadScope(19, -3);
         }
         assertSame(active.complex, engine.getComplex());
         assertNull(IrisContext.get());
@@ -242,7 +242,7 @@ public class IrisEngineGenerationRuntimeScopeTest {
             }
         }
         engine.getCaveBiome(19, -3);
-        verify(router, times(3)).openCoordinateScope(19, -3);
+        verify(router, times(3)).openReadScope(19, -3);
     }
 
     @Test
@@ -274,7 +274,7 @@ public class IrisEngineGenerationRuntimeScopeTest {
         when(caves.get(19D, -3D)).thenReturn(cave);
         when(surfaces.get(19D, -3D)).thenReturn(surface);
         when(regions.get(19D, -3D)).thenReturn(region);
-        when(router.openCoordinateScope(19, -3)).thenAnswer(invocation -> {
+        when(router.openReadScope(19, -3)).thenAnswer(invocation -> {
             assertSame(active.complex, engine.getComplex());
             IrisEngine.GenerationRuntimeScope runtimeScope = engine.openGenerationRuntimeScope(binding);
             GenerationHistoryRuntimeRouter.CoordinateScope coordinateScope = mock(GenerationHistoryRuntimeRouter.CoordinateScope.class);
@@ -292,7 +292,7 @@ public class IrisEngineGenerationRuntimeScopeTest {
             assertSame(region, engine.getRegion(19, 20, -3));
             assertSame(active.complex, engine.getComplex());
         }
-        verify(router, times(4)).openCoordinateScope(19, -3);
+        verify(router, times(4)).openReadScope(19, -3);
         verifyNoInteractions(saved);
         assertNull(IrisContext.get());
     }
@@ -318,7 +318,7 @@ public class IrisEngineGenerationRuntimeScopeTest {
         }
         verify(saved).resolveCaveBase(19, -3);
         verify(saved, times(2)).resolve(19, -64, -3, true);
-        verify(router, never()).openCoordinateScope(anyInt(), anyInt());
+        verify(router, never()).openReadScope(anyInt(), anyInt());
         assertNull(IrisContext.get());
     }
 
@@ -839,7 +839,7 @@ public class IrisEngineGenerationRuntimeScopeTest {
         assertSame(environment.biome(), engine.getSurfaceBiome(19, -3));
         assertSame(environment.region(), engine.getRegion(19, -3));
         assertSame(environment.region(), engine.getRegion(19, 20, -3));
-        verify(router, never()).openCoordinateScope(anyInt(), anyInt());
+        verify(router, never()).openReadScope(anyInt(), anyInt());
     }
 
     @Test
@@ -855,7 +855,7 @@ public class IrisEngineGenerationRuntimeScopeTest {
 
         assertSame(failure, assertThrows(SavedBiomeUnavailableException.class,
                 () -> engine.getBiome(19, 20, -3)));
-        verify(router, never()).openCoordinateScope(anyInt(), anyInt());
+        verify(router, never()).openReadScope(anyInt(), anyInt());
     }
 
     @Test

core/src/test/java/art/arcane/iris/generation/terrain/IrisDimensionCarvingResolverParityTest.java

@@ -494,12 +494,11 @@ public class IrisDimensionCarvingResolverParityTest {
         assertSame(fixture.entry(), IrisDimensionCarvingResolver.resolveRootEntry(
                 fixture.engine(), 80, state));
 
-        Field rootEntriesField = IrisDimensionCarvingResolver.State.class
+        Field rootsField = IrisDimensionCarvingResolver.State.class.getDeclaredField("roots");
-                .getDeclaredField("rootEntriesByWorldY");
+        rootsField.setAccessible(true);
-        rootEntriesField.setAccessible(true);
         System.gc();
 
-        assertSame(fixture.entry(), ((Map<?, ?>) rootEntriesField.get(state)).get(80));
+        assertSame(fixture.entry(), ((IrisDimensionCarvingEntry[]) rootsField.get(state))[80]);
     }
 
     private RetainedFixture createRetainedFixture() {

core/src/test/java/art/arcane/iris/world/history/GenerationHistoryRuntimeRouterRoutingTest.java

@@ -16,6 +16,7 @@ import org.mockito.MockedStatic;
 import java.io.File;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -350,6 +351,11 @@ public final class GenerationHistoryRuntimeRouterRoutingTest extends GenerationH
         when(engine.getBiomeOrMantle(anyInt(), anyInt(), anyInt())).thenReturn(biome);
         when(engine.getRegion(anyInt(), anyInt())).thenReturn(region);
         when(engine.getRegion(anyInt(), anyInt(), anyInt())).thenReturn(region);
+        doAnswer(invocation -> {
+            Arrays.fill((IrisBiome[]) invocation.getArgument(3), biome);
+            Arrays.fill((IrisRegion[]) invocation.getArgument(4), region);
+            return null;
+        }).when(engine).getBiomeOrMantleColumn(anyInt(), anyInt(), anyInt(), any(), any());
         EngineMantle engineMantle = mock(EngineMantle.class);
         @SuppressWarnings("unchecked")
         Mantle<Matter> mantle = mock(Mantle.class);
@@ -429,4 +435,44 @@ public final class GenerationHistoryRuntimeRouterRoutingTest extends GenerationH
         verify(engine, times(2)).openGenerationRuntimeScope(first);
         router.close();
     }
+
+    @Test
+    public void readScopeBorrowsTheBoundRouteRuntimeForOtherChunks() throws Exception {
+        Path world = temporaryFolder.newFolder("router-read-world").toPath();
+        Path pack = createPack("router-read-pack", "alpha");
+        GenerationHistory history = createHistory(world, pack);
+        IrisEngine engine = mock(IrisEngine.class);
+        FakeRuntimeFactory runtimes = new FakeRuntimeFactory();
+        IrisEngine.GenerationRuntimeBinding first = runtimes.binding(history, history.activeActivation());
+        when(engine.getActiveGenerationRuntimeBinding()).thenReturn(first);
+        AtomicReference<IrisEngine.GenerationRuntimeBinding> scoped = installScopeTracking(engine);
+        when(engine.captureGenerationRuntimeBinding()).thenAnswer(invocation -> scoped.get());
+        GenerationHistoryRuntimeRouter router = GenerationHistoryRuntimeRouter.attach(
+                engine,
+                history,
+                (ignored, blockX, blockZ) -> signature(blockX, blockZ),
+                runtimes
+        );
+
+        try (GenerationHistoryRuntimeRouter.RuntimeRoute route = router.openRoute(-1, -2);
+             GenerationHistoryRuntimeRouter.RuntimeRoute.RuntimeScope ignored = route.openRuntimeScope()) {
+            try (GenerationHistoryRuntimeRouter.CoordinateScope same = router.openReadScope(-1, -17)) {
+                assertSame(route.activation(), same.activation());
+            }
+            try (GenerationHistoryRuntimeRouter.CoordinateScope neighbour = router.openReadScope(16, 0)) {
+                assertEquals(1, neighbour.chunkX());
+                assertEquals(0, neighbour.chunkZ());
+                assertFalse(neighbour.claimGeneratedSemantics());
+                assertSame(first, scoped.get());
+            }
+            verify(engine, times(1)).openGenerationRuntimeScope(first);
+
+            scoped.set(runtimes.binding(history, history.activeActivation()));
+            try (GenerationHistoryRuntimeRouter.CoordinateScope rebound = router.openReadScope(16, 0)) {
+                assertSame(route.activation(), rebound.activation());
+            }
+            verify(engine, times(2)).openGenerationRuntimeScope(first);
+        }
+        router.close();
+    }
 }

core/src/test/java/art/arcane/iris/world/history/GenerationSemanticIndexTest.java

@@ -206,6 +206,27 @@ public final class GenerationSemanticIndexTest {
                 new ChunkGenerationSemantics.BlockPosition(-520, 80, -8), 4)).isEmpty());
     }
 
+    @Test
+    public void claimsDeferRegionSummariesUntilAQueryReadsThem() throws Exception {
+        Path root = temporaryFolder.newFolder("lazy-summaries").toPath();
+        GenerationSemanticIndex index = GenerationSemanticIndex.initialize(root);
+
+        index.claimAndPersist(ChunkGenerationSemantics.builder(-33, -1, 1L).addObject("iris:first").seal().build());
+        assertEquals(0, index.cachedSummaryCount());
+        assertEquals("iris:first", requiredMatch(index, GenerationSemanticIndex.SemanticKind.OBJECT, "iris:first").key());
+        assertEquals(1, index.cachedSummaryCount());
+
+        index.claimAndPersist(ChunkGenerationSemantics.builder(-34, -1, 1L).addObject("iris:second").seal().build());
+        assertEquals(0, index.cachedSummaryCount());
+        assertEquals("iris:second", requiredMatch(index, GenerationSemanticIndex.SemanticKind.OBJECT, "iris:second").key());
+        assertEquals("iris:first", requiredMatch(index, GenerationSemanticIndex.SemanticKind.OBJECT, "iris:first").key());
+        assertEquals(2, sealedClaims(index, 1L).size());
+
+        GenerationSemanticIndex reopened = GenerationSemanticIndex.load(root);
+        assertEquals("iris:second", requiredMatch(reopened, GenerationSemanticIndex.SemanticKind.OBJECT, "iris:second").key());
+        assertEquals(index.recordsSnapshot(), reopened.recordsSnapshot());
+    }
+
     @Test
     public void conflictingActivationsAndFactsAfterSealAreRejectedWithoutDiskChanges() throws Exception {
         Path dimensionRoot = temporaryFolder.newFolder("sealed").toPath();

core/src/test/java/art/arcane/iris/world/history/SavedBiomeCaptureTest.java

@@ -11,9 +11,11 @@ import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyDouble;
 import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.Mockito.RETURNS_DEEP_STUBS;
+import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.doCallRealMethod;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verifyNoInteractions;
@@ -92,6 +94,7 @@ public class SavedBiomeCaptureTest {
         when(engine.getSurfaceBiome(anyInt(), anyInt())).thenReturn(host);
         when(engine.getCaveBiome(anyInt(), anyInt())).thenReturn(host);
         when(engine.getBiomeOrMantle(anyInt(), anyInt(), anyInt())).thenReturn(host);
+        columnsFromPointLookups(engine);
         FloatingBiomeOverlay floating = new FloatingBiomeOverlay(16);
         FloatingBiomeOverlay.Identity childIdentity = new FloatingBiomeOverlay.Identity(child.getLoadKey(), region.getLoadKey());
         floating.record(0, 8, 0, childIdentity);
@@ -135,6 +138,7 @@ public class SavedBiomeCaptureTest {
         when(engine.getSurfaceBiome(anyInt(), anyInt())).thenAnswer(call -> (int) call.getArgument(0) == -15 ? right : left);
         when(engine.getCaveBiome(anyInt(), anyInt())).thenReturn(cave);
         when(engine.getBiomeOrMantle(anyInt(), anyInt(), anyInt())).thenAnswer(call -> (int) call.getArgument(1) < 8 ? lower : upper);
+        columnsFromPointLookups(engine);
 
         SavedBiomeChunk chunk = SavedBiomeCapture.capture(engine, stage, historical, null);
 
@@ -167,9 +171,25 @@ public class SavedBiomeCaptureTest {
         doCallRealMethod().when(engine).getBiomeOrMantle(anyInt(), anyInt(), anyInt());
         when(engine.getCaveOrMantleBiome(anyInt(), anyInt(), anyInt()))
                 .thenAnswer(call -> engine.getCaveBiome(call.getArgument(0), call.getArgument(2)));
+        columnsFromPointLookups(engine);
         return engine;
     }
 
+    private static void columnsFromPointLookups(Engine engine) {
+        doAnswer(call -> {
+            int x = call.getArgument(0);
+            int z = call.getArgument(1);
+            int step = call.getArgument(2);
+            IrisBiome[] biomes = call.getArgument(3);
+            IrisRegion[] regions = call.getArgument(4);
+            for (int index = 0; index < biomes.length; index++) {
+                biomes[index] = engine.getBiomeOrMantle(x, index * step, z);
+                regions[index] = engine.getRegion(x, index * step, z);
+            }
+            return null;
+        }).when(engine).getBiomeOrMantleColumn(anyInt(), anyInt(), anyInt(), any(), any());
+    }
+
     private static GenerationHistory.GenerationStage stage() {
         GenerationHistory.GenerationStage stage = mock(GenerationHistory.GenerationStage.class);
         when(stage.chunkX()).thenReturn(-1);

core/src/test/java/art/arcane/iris/world/history/SavedTerrainCaptureEquivalenceTest.java

@@ -0,0 +1,234 @@
+package art.arcane.iris.world.history;
+
+import org.junit.Test;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.OptionalInt;
+import java.util.Random;
+import java.util.TreeSet;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+
+public class SavedTerrainCaptureEquivalenceTest {
+    private static final int MINIMUM_Y = -64;
+    private static final int HEIGHT = 384;
+    private static final Comparator<BoundaryColumnGeometry.Voxel> VOXEL_ORDER = Comparator
+            .comparing(BoundaryColumnGeometry.Voxel::stateKey)
+            .thenComparing(BoundaryColumnGeometry.Voxel::phase)
+            .thenComparing(BoundaryColumnGeometry.Voxel::fluidStateKey)
+            .thenComparing(BoundaryColumnGeometry.Voxel::protectedContent);
+    private static final List<BoundaryColumnGeometry.Voxel> STATES = List.of(
+            voxel("minecraft:stone", BoundaryColumnGeometry.Phase.SOLID, "", false),
+            voxel("minecraft:deepslate", BoundaryColumnGeometry.Phase.SOLID, "", false),
+            voxel("minecraft:air", BoundaryColumnGeometry.Phase.AIR, "", false),
+            voxel("minecraft:cave_air", BoundaryColumnGeometry.Phase.AIR, "", false),
+            voxel("minecraft:water[level=0]", BoundaryColumnGeometry.Phase.FLUID, "minecraft:water[level=0]", false),
+            voxel("minecraft:lava[level=0]", BoundaryColumnGeometry.Phase.FLUID, "minecraft:lava[level=0]", false),
+            voxel("minecraft:oak_log[axis=y]", BoundaryColumnGeometry.Phase.SOLID, "", true),
+            voxel("minecraft:kelp", BoundaryColumnGeometry.Phase.SOLID, "minecraft:water[level=0]", true),
+            voxel("minecraft:stone", BoundaryColumnGeometry.Phase.SOLID, "", true));
+    private static final List<String> BIOMES = List.of("minecraft:plains", "minecraft:river",
+            "minecraft:lush_caves", "minecraft:deep_dark", "minecraft:dripstone_caves");
+
+    @Test
+    public void boundaryAndFullCapturesMatchTheReferenceEncoding() throws Exception {
+        Random random = new Random(20260928L);
+        for (int sample = 0; sample < 48; sample++) {
+            RandomSource source = new RandomSource(random, sample);
+            for (boolean boundaryOnly : new boolean[]{true, false}) {
+                SavedTerrainChunk expected = referenceCapture(-3, 7, source, boundaryOnly);
+                SavedTerrainChunk actual = boundaryOnly
+                        ? SavedTerrainChunk.captureBoundary(-3, 7, MINIMUM_Y, HEIGHT, "minecraft:noise", source)
+                        : SavedTerrainChunk.capture(-3, 7, MINIMUM_Y, HEIGHT, "minecraft:noise", source);
+                assertSameTerrain(expected, actual);
+                assertArrayEquals(NativeTerrainReceipt.encode(expected, 1L, "epoch"),
+                        NativeTerrainReceipt.encode(actual, 1L, "epoch"));
+            }
+        }
+    }
+
+    @Test
+    public void geometryMatchesTheReferenceOnWidePalettes() {
+        Random random = new Random(7L);
+        for (int sample = 0; sample < 32; sample++) {
+            ArrayList<BoundaryColumnGeometry.Voxel> voxels = new ArrayList<>(HEIGHT);
+            int distinct = 1 + random.nextInt(sample < 16 ? 12 : 200);
+            while (voxels.size() < HEIGHT) {
+                int state = random.nextInt(distinct);
+                BoundaryColumnGeometry.Voxel voxel = voxel("minecraft:block_" + state,
+                        BoundaryColumnGeometry.Phase.values()[state % 2], "", state % 3 == 0);
+                int end = Math.min(HEIGHT, voxels.size() + 1 + random.nextInt(4));
+                while (voxels.size() < end) {
+                    voxels.add(voxel);
+                }
+            }
+            assertEquals(referenceGeometry(MINIMUM_Y, voxels), BoundaryColumnGeometry.fromVoxels(MINIMUM_Y, voxels));
+        }
+    }
+
+    private static void assertSameTerrain(SavedTerrainChunk expected, SavedTerrainChunk actual) {
+        assertEquals(expected.chunkX(), actual.chunkX());
+        assertEquals(expected.chunkZ(), actual.chunkZ());
+        assertEquals(expected.nativeStatus(), actual.nativeStatus());
+        for (int x = 0; x < 16; x++) {
+            for (int z = 0; z < 16; z++) {
+                assertEquals(expected.hasColumn(x, z), actual.hasColumn(x, z));
+                if (!expected.hasColumn(x, z)) {
+                    continue;
+                }
+                TerrainBoundarySignature left = expected.column(-48 + x, 112 + z);
+                TerrainBoundarySignature right = actual.column(-48 + x, 112 + z);
+                assertEquals(left.column(), right.column());
+                assertEquals(left.samples(), right.samples());
+                assertEquals(left.geometry(), right.geometry());
+            }
+        }
+    }
+
+    private static SavedTerrainChunk referenceCapture(int chunkX, int chunkZ, SavedTerrainChunk.VoxelSource source,
+                                                      boolean boundaryOnly) throws IOException {
+        List<TerrainBoundarySignature> columns = new ArrayList<>(256);
+        for (int x = 0; x < 16; x++) {
+            for (int z = 0; z < 16; z++) {
+                if (boundaryOnly && x != 0 && x != 15 && z != 0 && z != 15) {
+                    columns.add(null);
+                    continue;
+                }
+                List<BoundaryColumnGeometry.Voxel> voxels = new ArrayList<>(HEIGHT);
+                Map<String, Short> biomePalette = new LinkedHashMap<>();
+                short[] biomeIndices = new short[HEIGHT / 4];
+                int surface = 0;
+                int floor = 0;
+                int fluid = -1;
+                for (int offset = 0; offset < HEIGHT; offset++) {
+                    int y = MINIMUM_Y + offset;
+                    BoundaryColumnGeometry.Voxel voxel = Objects.requireNonNull(source.voxel(x, y, z), "voxel");
+                    voxels.add(voxel);
+                    if (voxel.phase() != BoundaryColumnGeometry.Phase.AIR) {
+                        surface = offset;
+                    }
+                    if (voxel.phase() == BoundaryColumnGeometry.Phase.SOLID) {
+                        floor = offset;
+                    }
+                    if (!voxel.fluidStateKey().isEmpty()) {
+                        fluid = offset;
+                    }
+                    if (offset % 4 == 0) {
+                        String biome = Objects.requireNonNull(source.biome(x, y, z), "physical biome");
+                        Short index = biomePalette.get(biome);
+                        if (index == null) {
+                            index = (short) biomePalette.size();
+                            biomePalette.put(biome, index);
+                        }
+                        biomeIndices[offset / 4] = index;
+                    }
+                }
+                BoundaryColumnGeometry geometry = referenceGeometry(MINIMUM_Y, voxels);
+                OptionalInt groundSurface = source.groundSurface(x, z);
+                if (groundSurface.isPresent()) {
+                    floor = geometry.surfaceOffsetNear(groundSurface.getAsInt());
+                    surface = Math.max(floor, fluid);
+                }
+                columns.add(new TerrainBoundarySignature(
+                        new TerrainBoundarySignature.Column(chunkX * 16 + x, chunkZ * 16 + z, surface, floor,
+                                fluid > floor ? OptionalInt.of(fluid) : OptionalInt.empty(), OptionalInt.empty()),
+                        new TerrainBoundarySignature.Samples(
+                                new TerrainBoundarySignature.VerticalLayout(MINIMUM_Y, 4, biomeIndices.length),
+                                new TerrainBoundarySignature.BiomeEncoding(List.copyOf(biomePalette.keySet()), biomeIndices)),
+                        geometry));
+            }
+        }
+        return new SavedTerrainChunk(chunkX, chunkZ, "minecraft:noise", columns);
+    }
+
+    private static BoundaryColumnGeometry referenceGeometry(int minimumY, List<BoundaryColumnGeometry.Voxel> voxels) {
+        TreeSet<BoundaryColumnGeometry.Voxel> used = new TreeSet<>(VOXEL_ORDER);
+        BoundaryColumnGeometry.Voxel previous = null;
+        for (BoundaryColumnGeometry.Voxel voxel : voxels) {
+            if (previous == null || !previous.equals(voxel)) {
+                used.add(voxel);
+                previous = voxel;
+            }
+        }
+        List<BoundaryColumnGeometry.Voxel> palette = List.copyOf(used);
+        Map<BoundaryColumnGeometry.Voxel, Short> indices = new HashMap<>(palette.size());
+        for (int index = 0; index < palette.size(); index++) {
+            indices.put(palette.get(index), (short) index);
+        }
+        int[] ends = new int[voxels.size()];
+        short[] values = new short[voxels.size()];
+        int runCount = 0;
+        previous = null;
+        for (int offset = 0; offset < voxels.size(); offset++) {
+            BoundaryColumnGeometry.Voxel voxel = voxels.get(offset);
+            if (previous == null || !previous.equals(voxel)) {
+                values[runCount++] = indices.get(voxel);
+                previous = voxel;
+            }
+            ends[runCount - 1] = offset + 1;
+        }
+        return new BoundaryColumnGeometry(minimumY, palette, Arrays.copyOf(ends, runCount), Arrays.copyOf(values, runCount));
+    }
+
+    private static BoundaryColumnGeometry.Voxel voxel(String state, BoundaryColumnGeometry.Phase phase, String fluid,
+                                                      boolean protectedContent) {
+        return new BoundaryColumnGeometry.Voxel(state, phase, fluid, protectedContent);
+    }
+
+    private static final class RandomSource implements SavedTerrainChunk.VoxelSource {
+        private final BoundaryColumnGeometry.Voxel[][] voxels = new BoundaryColumnGeometry.Voxel[256][HEIGHT];
+        private final String[][] biomes = new String[256][HEIGHT];
+        private final int[] ground = new int[256];
+
+        private RandomSource(Random random, int sample) {
+            for (int column = 0; column < 256; column++) {
+                int offset = 0;
+                while (offset < HEIGHT) {
+                    BoundaryColumnGeometry.Voxel state = STATES.get(random.nextInt(STATES.size()));
+                    BoundaryColumnGeometry.Voxel copy = random.nextBoolean() ? state
+                            : new BoundaryColumnGeometry.Voxel(new String(state.stateKey()), state.phase(),
+                            new String(state.fluidStateKey()), state.protectedContent());
+                    int end = Math.min(HEIGHT, offset + 1 + random.nextInt(sample % 3 == 0 ? 3 : 64));
+                    while (offset < end) {
+                        voxels[column][offset++] = copy;
+                    }
+                }
+                offset = 0;
+                while (offset < HEIGHT) {
+                    String biome = BIOMES.get(random.nextInt(BIOMES.size()));
+                    String copy = random.nextBoolean() ? biome : new String(biome);
+                    int end = Math.min(HEIGHT, offset + 4 + random.nextInt(96));
+                    while (offset < end) {
+                        biomes[column][offset++] = copy;
+                    }
+                }
+                ground[column] = sample % 4 == 0 ? -1 : random.nextInt(HEIGHT);
+            }
+        }
+
+        @Override
+        public OptionalInt groundSurface(int localX, int localZ) {
+            int value = ground[localX * 16 + localZ];
+            return value < 0 ? OptionalInt.empty() : OptionalInt.of(value);
+        }
+
+        @Override
+        public BoundaryColumnGeometry.Voxel voxel(int localX, int worldY, int localZ) {
+            return voxels[localX * 16 + localZ][worldY - MINIMUM_Y];
+        }
+
+        @Override
+        public String biome(int localX, int worldY, int localZ) {
+            return biomes[localX * 16 + localZ][worldY - MINIMUM_Y];
+        }
+    }
+}