Skip floating fields for plain parents

- parent biome lookups read the biome stream directly instead of building the boundary field
- fields are only built where a parent with floating children needs edge distances

core/src/main/java/art/arcane/iris/generation/biome/FloatingIslandBoundarySampler.java

@@ -48,7 +48,7 @@ public final class FloatingIslandBoundarySampler {
     }
 
     public @Nullable IrisBiome parent(int x, int z) {
-        return parentField(x, z, EDGE_TAPER_WIDTH).parent(x, z);
+        return source.sample(x, z);
     }
 
     public double edgeFade(IrisBiome parent, int x, int z) {
@@ -230,10 +230,6 @@ public final class FloatingIslandBoundarySampler {
             build(source);
         }
 
-        private @Nullable IrisBiome parent(int x, int z) {
-            return parents[geometry.index(x - minX, z - minZ)];
-        }
-
         private int edgeDistance(IrisBiome expected, int x, int z) {
             int index = geometry.index(x - minX, z - minZ);
             if (!sameBiome(expected, parents[index]) || !viable[index]) {

core/src/test/java/art/arcane/iris/generation/biome/FloatingIslandBoundarySamplerTest.java

@@ -103,20 +103,18 @@ public class FloatingIslandBoundarySamplerTest {
     }
 
     @Test
-    public void parent_cachesResolvedBiomeColumns() {
+    public void parent_readsOnlyTheQueriedColumnWithoutBuildingTheBoundaryField() {
         IrisBiome parent = new IrisBiome();
+        IrisBiome other = new IrisBiome();
         AtomicInteger calls = new AtomicInteger();
         FloatingIslandBoundarySampler sampler = new FloatingIslandBoundarySampler((x, z) -> {
             calls.incrementAndGet();
-            return parent;
+            return x == 12 && z == -9 ? parent : other;
         });
 
         assertSame(parent, sampler.parent(12, -9));
-        int firstReadCount = calls.get();
-        assertSame(parent, sampler.parent(12, -9));
-        assertEquals(firstReadCount, calls.get());
-        int rawWidth = 16 + (FloatingIslandBoundarySampler.EDGE_FADE_RADIUS * 2) + 2;
-        assertEquals(rawWidth * rawWidth, firstReadCount);
+        assertSame(other, sampler.parent(13, -9));
+        assertEquals(2, calls.get());
     }
 
     @Test