Trim cave decoration markers

- Stop writing cave ceiling markers, which nothing reads
- Write cave floor markers only when the dimension has cave spawners
- Reuse the zone floor subterrain cell for zone decoration

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

@@ -971,6 +971,7 @@ public class IrisCarveModifier extends EngineAssignedModifier<NativeBlockState>
             }
         }
         CaveInputs resolver = CaveInputs.forContentChunk(getEngine(), blockX >> 4, blockZ >> 4);
+        boolean caveFloorMarkers = getDimension().hasUndergroundSpawners(getEngine());
         Long2ObjectOpenHashMap<IrisBiome> caveBiomes = new Long2ObjectOpenHashMap<>(256);
         Map<String, IrisBiome> customBiomes = new HashMap<>();
         int width = output.getWidth();
@@ -993,13 +994,11 @@ public class IrisCarveModifier extends EngineAssignedModifier<NativeBlockState>
                             CaveZone zone = new CaveZone();
                             zone.setFloor(floor);
                             zone.setCeiling(y - 1);
-                            if (zone.isValid(resolver.height)
-                                    && (subterrainCell(worldX, floor, worldZ).occupied()
+                            SubterrainCell floorCell = zone.isValid(resolver.height)
+                                    ? subterrainCell(worldX, floor, worldZ) : null;
+                            if (floorCell != null && (floorCell.occupied()
                                     || !isNaturalTerrainOpening(getComplex(), worldX, floor, worldZ, context))) {
-                                if (markerRoll(worldX, zone.ceiling, worldZ, 0x9E3779B97F4A7C15L)) {
-                                    mantle.set(worldX, zone.ceiling, worldZ, MarkerMatter.CAVE_CEILING);
-                                }
-                                if (markerRoll(worldX, zone.floor, worldZ, 0xC2B2AE3D27D4EB4FL)) {
+                                if (caveFloorMarkers && markerRoll(worldX, zone.floor, worldZ, 0xC2B2AE3D27D4EB4FL)) {
                                     mantle.set(worldX, zone.floor, worldZ, MarkerMatter.CAVE_FLOOR);
                                 }
                                 IrisBiome floorBiome = resolveCaveBoundaryBiome(terrain, localX, floor, localZ,
@@ -1007,7 +1006,7 @@ public class IrisCarveModifier extends EngineAssignedModifier<NativeBlockState>
                                 IrisBiome ceilingBiome = resolveCaveBoundaryBiome(terrain, localX, y - 1, localZ,
                                         worldX, worldZ, resolver, caveBiomes, customBiomes);
                                 decorateZone(output, zone, localX, localZ, worldX, worldZ,
-                                        floorBiome, ceilingBiome);
+                                        floorBiome, ceilingBiome, floorCell);
                                 if (extent != null) {
                                     top = extent.highestStoredY(localX, localZ);
                                 }
@@ -1023,9 +1022,8 @@ public class IrisCarveModifier extends EngineAssignedModifier<NativeBlockState>
         restoreSubterrainSolids(output, blockX >> 4, blockZ >> 4, true);
     }
 
-    private void decorateZone(Hunk<NativeBlockState> output, CaveZone zone,
-                              int rx, int rz, int xx, int zz, IrisBiome floorBiome, IrisBiome ceilingBiome) {
-        SubterrainCell feature = subterrainCell(xx, zone.getFloor(), zz);
+    private void decorateZone(Hunk<NativeBlockState> output, CaveZone zone, int rx, int rz, int xx, int zz,
+                              IrisBiome floorBiome, IrisBiome ceilingBiome, SubterrainCell feature) {
         boolean reservedPassage = feature.owned() && feature.room().reservedPassage();
         int maxY = output.getHeight();
         IrisDecorator[] surfaceDecorators = floorBiome == null

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

@@ -7,6 +7,7 @@ import art.arcane.iris.generation.decoration.IrisCeilingDecorator;
 import art.arcane.iris.generation.decoration.IrisSurfaceDecorator;
 import art.arcane.iris.generation.runtime.Engine;
 import art.arcane.iris.generation.runtime.SeedManager;
+import art.arcane.iris.generation.terrain.IrisDimension;
 import art.arcane.iris.generation.terrain.transform.TerrainTransformRuntime;
 import art.arcane.iris.generation.terrain.Terrain3DColumn;
 import art.arcane.iris.generation.context.ChunkContext;
@@ -72,12 +73,17 @@ public class IrisNaturalCaveScanTest {
 
     @Test
     public void narrowScanPreservesDecoratedBlocksMarkersAndMutationOrder() throws Exception {
-        verifyScan(5, 3);
+        verifyScan(5, 3, true);
     }
 
     @Test
     public void chunkScanPreservesDecoratedBlocksMarkersAndMutationOrder() throws Exception {
-        verifyScan(16, 16);
+        verifyScan(16, 16, true);
+    }
+
+    @Test
+    public void scanWithoutCaveSpawnersWritesNoCaveMarkers() throws Exception {
+        verifyScan(16, 16, false);
     }
 
     @Test
@@ -277,8 +283,8 @@ public class IrisNaturalCaveScanTest {
         assertEquals(List.of("floor:0:0:3:3", "ceiling:0:0:8:3"), fixture.calls);
     }
 
-    private static void verifyScan(int width, int depth) throws Exception {
-        Fixture fixture = new Fixture();
+    private static void verifyScan(int width, int depth, boolean caveSpawners) throws Exception {
+        Fixture fixture = new Fixture(false, caveSpawners);
         Hunk<NativeBlockState> output = fixture.output(width, depth);
         List<String> writes = new ArrayList<>();
         fixture.modifier.decorateNaturalCaves(-32, 48,
@@ -302,10 +308,8 @@ public class IrisNaturalCaveScanTest {
                         }
                     }
                     expectedWrites.add(x + ":" + ceiling + ":" + z + ":minecraft:calcite");
-                    if ((boolean) markerRoll.invoke(fixture.modifier, x - 32, ceiling, z + 48, 0x9E3779B97F4A7C15L)) {
-                        expectedMarkers.add((x - 32) + ":" + ceiling + ":" + (z + 48) + ":" + MarkerMatter.CAVE_CEILING);
-                    }
-                    if ((boolean) markerRoll.invoke(fixture.modifier, x - 32, floor, z + 48, 0xC2B2AE3D27D4EB4FL)) {
+                    if (caveSpawners
+                            && (boolean) markerRoll.invoke(fixture.modifier, x - 32, floor, z + 48, 0xC2B2AE3D27D4EB4FL)) {
                         expectedMarkers.add((x - 32) + ":" + floor + ":" + (z + 48) + ":" + MarkerMatter.CAVE_FLOOR);
                     }
                 }
@@ -327,7 +331,7 @@ public class IrisNaturalCaveScanTest {
         assertEquals(expectedCalls, fixture.calls);
         assertEquals(expectedWrites, writes);
         assertEquals(expectedMarkers, fixture.markers);
-        assertTrue("fixture must exercise marker writes", !expectedMarkers.isEmpty());
+        assertEquals("fixture must exercise marker writes", caveSpawners, !expectedMarkers.isEmpty());
         verify(fixture.mantle).useChunk(-2, 3);
         verify(fixture.chunk).release();
     }
@@ -361,9 +365,16 @@ public class IrisNaturalCaveScanTest {
             this(false);
         }
 
-        @SuppressWarnings("unchecked")
         private Fixture(boolean buildAboveTop) throws Exception {
+            this(buildAboveTop, true);
+        }
+
+        @SuppressWarnings("unchecked")
+        private Fixture(boolean buildAboveTop, boolean caveSpawners) throws Exception {
             Engine engine = mock(Engine.class);
+            IrisDimension dimension = mock(IrisDimension.class);
+            doReturn(dimension).when(engine).getDimension();
+            doReturn(caveSpawners).when(dimension).hasUndergroundSpawners(engine);
             EngineMantle engineMantle = mock(EngineMantle.class);
             mantle = mock(Mantle.class);
             chunk = mock(MantleChunk.class);