Batch history biome reads

- saved biome capture resolves each quart column through one engine call
- column-invariant height, region, surface and cave fallback resolved once
- cavern reads use one pinned mantle chunk per column
- saved biome cells interned per capture
- engine getters borrow the bound route runtime for other chunks instead of opening a stage

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());
-            if (biome != null) {
-                return biome;
+            return getData().getBiomeLoader().load(hydrology.floodedBiomeKey());
+        }
+        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 = naturalFallback || dimensionStackContext == null
-                ? naturalFallback
-                        ? getComplex().naturalSurfaceBiome(x, z)
-                        : getSurfaceBiome(x, z)
-                : getComplex().getTrueBiomeStream().get(x, z);
-        int surfaceY = naturalFallback
+        IrisBiome surfaceBiome = caveDepthSurfaceBiome(x, z, naturalFallback);
+        int surfaceY = caveDepthSurfaceY(x, z, naturalFallback);
+        return resolveDepthCaveBiome(x, y, z, surfaceBiome, surfaceY);
+    }
+
+    private IrisBiome caveDepthSurfaceBiome(int x, int z, boolean 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/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/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,
-                                                             SavedBiomeRuntime saved, Map<Long, Optional<SavedBiomeChunk>> historical, FloatingBiomeOverlay floating) throws IOException {
-        Engine engine = column.engine();
-        int minimumY = engine.getMinHeight();
-        int maximumY = minimumY + engine.getHeight();
+    private static List<SavedBiomeChunk.Span> captureVertical(Column column, int blockX, int blockZ, Cells cells,
+                                                             TransitionGenerationPlan transition, SavedBiomeRuntime saved,
+                                                             Map<Long, Optional<SavedBiomeChunk>> historical, FloatingBiomeOverlay floating) throws IOException {
+        column.engine().getBiomeOrMantleColumn(blockX, blockZ, 4, column.biomes(), column.regions());
+        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) {
-            IrisBiome biome = engine.getBiomeOrMantle(column.blockX(), worldY - minimumY, column.blockZ());
-            IrisRegion region = engine.getRegion(column.blockX(), worldY - minimumY, column.blockZ());
-            SavedBiomeChunk.Cell current = cell(column.activationId(), biome, region);
+        for (int index = 0; index < column.biomes().length; index++) {
+            int worldY = minimumY + index * 4;
+            SavedBiomeChunk.Cell current = cells.cell(column.biomes()[index], column.regions()[index]);
             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) {