Captured cave biomes in content

- decorateNaturalCaves resolves coordinates of its own chunk through the captured column path; other coordinates keep the history dispatch

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

@@ -880,7 +880,7 @@ public class IrisCarveModifier extends EngineAssignedModifier<NativeBlockState>
                 chunk.release();
             }
         }
-        CaveInputs resolver = new CaveInputs(getEngine());
+        CaveInputs resolver = CaveInputs.forContentChunk(getEngine(), blockX >> 4, blockZ >> 4);
         Long2ObjectOpenHashMap<IrisBiome> caveBiomes = new Long2ObjectOpenHashMap<>(256);
         Map<String, IrisBiome> customBiomes = new HashMap<>();
         int width = output.getWidth();
@@ -1163,19 +1163,39 @@ public class IrisCarveModifier extends EngineAssignedModifier<NativeBlockState>
         private final ProceduralStream<IrisBiome> caveBiomes;
         private final ProceduralStream<Double> heights;
         private final CaveColumn[] columns;
+        private final boolean chunkLimited;
+        private final int chunkX;
+        private final int chunkZ;
 
         CaveInputs(Engine engine) {
+            this(engine, false, 0, 0);
+        }
+
+        /**
+         * Inputs for the content stage of one chunk. A coordinate inside that chunk resolves under the chunk's
+         * own generation route, exactly the binding the natural terrain stage samples with, so it takes the
+         * captured column path; any other coordinate keeps the per-coordinate history dispatch.
+         */
+        static CaveInputs forContentChunk(Engine engine, int chunkX, int chunkZ) {
+            return new CaveInputs(engine, true, chunkX, chunkZ);
+        }
+
+        private CaveInputs(Engine engine, boolean contentChunk, int chunkX, int chunkZ) {
             this.engine = engine;
             complex = engine.getComplex();
             dimension = engine.getDimension();
             data = engine.getData();
             height = engine.getHeight();
             IrisContext context = IrisContext.get();
-            boolean scoped = engine instanceof IrisEngine irisEngine
+            boolean generating = engine instanceof IrisEngine irisEngine
                     && irisEngine.hasGenerationRuntimeScope() && !engine.getPlatformHooks().isMainThread()
                     && context != null && context.getChunkContext() != null
-                    && context.getChunkContext().getComplex() == complex
-                    && context.getChunkContext().isNaturalTerrain();
+                    && context.getChunkContext().getComplex() == complex;
+            boolean natural = generating && context.getChunkContext().isNaturalTerrain();
+            boolean scoped = natural || generating && contentChunk;
+            this.chunkLimited = !natural;
+            this.chunkX = chunkX;
+            this.chunkZ = chunkZ;
             snapshot = scoped ? IrisDimensionCarvingResolver.snapshot(engine) : null;
             minimumY = scoped ? engine.getWorld().minHeight() : 0;
             stack = scoped ? engine.getDimensionStackContext() : null;
@@ -1186,7 +1206,7 @@ public class IrisCarveModifier extends EngineAssignedModifier<NativeBlockState>
         }
 
         IrisBiome resolve(int x, int y, int z) {
-            if (snapshot == null) {
+            if (snapshot == null || chunkLimited && ((x >> 4) != chunkX || (z >> 4) != chunkZ)) {
                 return engine.getCaveBiome(x, y, z, state);
             }
             IrisBiome configured = snapshot.resolveBiome(x, y + minimumY, z);

core/src/test/java/art/arcane/iris/generation/stage/IrisCarveModifierCaveInputsTest.java

@@ -26,6 +26,7 @@ import java.util.concurrent.atomic.AtomicInteger;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.Mockito.CALLS_REAL_METHODS;
@@ -122,6 +123,31 @@ public class IrisCarveModifierCaveInputsTest {
         }
     }
 
+    @Test
+    public void contentChunkCapturesOnlyItsOwnColumnsAndDispatchesTheRestThroughHistory() {
+        try (Fixture fixture = new Fixture()) {
+            when(fixture.context.isNaturalTerrain()).thenReturn(false);
+            IrisBiome historical = biome("historical", 0);
+            when(fixture.engine.getCaveBiome(anyInt(), anyInt(), anyInt(), any(IrisDimensionCarvingResolver.State.class))).thenReturn(historical);
+            IrisCarveModifier.CaveInputs inputs = IrisCarveModifier.CaveInputs.forContentChunk(fixture.engine, -2, 1);
+            IrisDimensionCarvingResolver.State state = new IrisDimensionCarvingResolver.State();
+            for (int x = -32; x <= -17; x++) {
+                for (int z = 16; z <= 31; z += 5) {
+                    for (int y : new int[]{0, 30, 33, 34, 39, 40}) {
+                        assertSame(fixture.scalar.getCaveBiome(x, y, z, state), inputs.resolve(x, y, z));
+                    }
+                }
+            }
+            int captured = fixture.samples.get();
+            assertTrue(captured > 0);
+            assertSame(historical, inputs.resolve(-33, 20, 16));
+            assertSame(historical, inputs.resolve(-16, 20, 16));
+            assertSame(historical, inputs.resolve(-17, 20, 15));
+            assertSame(historical, inputs.resolve(-17, 20, 32));
+            assertEquals(captured, fixture.samples.get());
+        }
+    }
+
     private static IrisBiome biome(String key, int depth) {
         IrisBiome biome = new IrisBiome();
         biome.setLoadKey(key);