Implement tiled biome distribution

docs/PORTING.md

@@ -323,6 +323,12 @@ Overworld-like surfaces together with the persisted Native or Single biome
 distribution. This prevents Nether terrain generation from leaking into newly
 generated Cave Age chunks.
 
+Version 0.2.22.0 applies Tiled Biome Distribution using two deterministic
+Age-seeded biomes in the legacy diagonal-checkerboard layout. Each square is
+16 chunks (256 blocks) wide, matching Mystcraft Legacy's coordinate shift, and
+uses Minecraft's serializable checkerboard biome source so the layout remains
+stable across server reloads.
+
 Version 0.2.14.0 restores the legacy Linking and Descriptive Book artwork for
 inventory items and gives each book its matching open-book texture when placed
 on a Book Stand. Return Linking Books created inside another Age also retain and

gradle.properties

@@ -35,7 +35,7 @@ mod_name=Rivencraft
 # The license of the mod. Review your options at https://choosealicense.com/. All Rights Reserved is the default.
 mod_license=LGPL-3.0-or-later
 # The mod version. Rivencraft uses the x.y.z.b policy documented in README.md.
-mod_version=0.2.21.1
+mod_version=0.2.22.0
 immersive_portals_version=6.0.7
 # The group ID for the mod. It is only important when publishing as an artifact to a Maven repository.
 # This should match the base package used for the mod sources.

src/main/java/net/dnorberg/rivencraft/book/AgeDefinition.java

@@ -21,7 +21,7 @@ public record AgeDefinition(
     public static final ResourceLocation RANDOM_VANILLA_PROFILE = ResourceLocation.fromNamespaceAndPath(
             Rivencraft.MOD_ID, "random_vanilla"
     );
-    public static final int CURRENT_GENERATION_VERSION = 9;
+    public static final int CURRENT_GENERATION_VERSION = 10;
 
     public AgeDefinition {
         Objects.requireNonNull(id, "id");

src/main/java/net/dnorberg/rivencraft/book/AgeDimensionService.java

@@ -6,10 +6,12 @@ import java.util.Optional;
 import java.util.OptionalLong;
 import java.util.List;
 import java.util.Comparator;
+import java.util.Collections;
 import net.dnorberg.rivencraft.Rivencraft;
 import net.dnorberg.rivencraft.compat.ImmersivePortalsChunkLoaders;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.GlobalPos;
+import net.minecraft.core.HolderSet;
 import net.minecraft.core.registries.Registries;
 import net.minecraft.resources.ResourceKey;
 import net.minecraft.resources.ResourceLocation;
@@ -23,6 +25,7 @@ import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.biome.Biomes;
 import net.minecraft.world.level.biome.Biome;
 import net.minecraft.world.level.biome.BiomeSource;
+import net.minecraft.world.level.biome.CheckerboardColumnBiomeSource;
 import net.minecraft.world.level.biome.FixedBiomeSource;
 import net.minecraft.world.level.biome.MultiNoiseBiomeSource;
 import net.minecraft.world.level.biome.MultiNoiseBiomeSourceParameterLists;
@@ -42,6 +45,7 @@ public final class AgeDimensionService {
     private static final int SURFACE_SEARCH_RADIUS = 16;
     private static final int FALLBACK_PLATFORM_Y = 63;
     private static final int CAVE_SPAWN_SEARCH_Y = 64;
+    private static final int TILED_BIOME_SCALE = 4;
 
     private AgeDimensionService() {
     }
@@ -278,16 +282,22 @@ public final class AgeDimensionService {
             AgeDefinition age,
             net.minecraft.core.HolderGetter<net.minecraft.world.level.biome.MultiNoiseBiomeSourceParameterList> biomeParameters
     ) {
-        if (age.traits().biomeDistribution() == AgeTraits.BiomeDistribution.SINGLE) {
-            List<net.minecraft.core.Holder.Reference<Biome>> biomes = server.registryAccess()
-                    .lookupOrThrow(Registries.BIOME)
-                    .listElements()
-                    .sorted(Comparator.comparing(holder -> holder.key().location().toString()))
-                    .toList();
-            if (!biomes.isEmpty()) {
-                int index = Math.floorMod(Long.hashCode(age.seed() ^ 0x53494E474C454249L), biomes.size());
-                return new FixedBiomeSource(biomes.get(index));
-            }
+        List<net.minecraft.core.Holder.Reference<Biome>> biomes = server.registryAccess()
+                .lookupOrThrow(Registries.BIOME)
+                .listElements()
+                .sorted(Comparator.comparing(holder -> holder.key().location().toString()))
+                .toList();
+        if (age.traits().biomeDistribution() == AgeTraits.BiomeDistribution.SINGLE && !biomes.isEmpty()) {
+            int index = Math.floorMod(Long.hashCode(age.seed() ^ 0x53494E474C454249L), biomes.size());
+            return new FixedBiomeSource(biomes.get(index));
+        }
+        if (age.traits().biomeDistribution() == AgeTraits.BiomeDistribution.TILED && biomes.size() >= 2) {
+            List<net.minecraft.core.Holder.Reference<Biome>> selected = new java.util.ArrayList<>(biomes);
+            Collections.shuffle(selected, new java.util.Random(age.seed() ^ 0x54494C454442494FL));
+            return new CheckerboardColumnBiomeSource(
+                    HolderSet.direct(List.of(selected.get(0), selected.get(1))),
+                    TILED_BIOME_SCALE
+            );
         }
         return MultiNoiseBiomeSource.createFromPreset(
                 biomeParameters.getOrThrow(MultiNoiseBiomeSourceParameterLists.OVERWORLD));

src/main/java/net/dnorberg/rivencraft/gametest/LinkingGameTests.java

@@ -155,6 +155,26 @@ public final class LinkingGameTests {
     public static void legacyBaseTerrainProfilesLoadRuntimeDimensions(GameTestHelper helper) {
         for (var profile : AgeGenerationProfiles.all()) {
             UUID id = UUID.randomUUID();
+            AgeTraits selectedTraits = AgeTraits.select(id.getMostSignificantBits());
+            AgeTraits traits = profile.equals(AgeGenerationProfiles.STANDARD)
+                    ? new AgeTraits(
+                            AgeTraits.BiomeDistribution.SINGLE,
+                            AgeTraits.Lighting.NORMAL,
+                            AgeTraits.Weather.NORMAL,
+                            1.0D,
+                            0.0F,
+                            0.0F
+                    )
+                    : profile.equals(AgeGenerationProfiles.AMPLIFIED)
+                            ? new AgeTraits(
+                                    AgeTraits.BiomeDistribution.TILED,
+                                    selectedTraits.lighting(),
+                                    selectedTraits.weather(),
+                                    selectedTraits.celestialPeriod(),
+                                    selectedTraits.celestialAngle(),
+                                    selectedTraits.celestialPhase()
+                            )
+                            : selectedTraits;
             AgeDefinition definition = new AgeDefinition(
                     id,
                     "Profile " + profile.getPath(),
@@ -166,16 +186,7 @@ public final class LinkingGameTests {
                             Rivencraft.MOD_ID, "gametest/" + profile.getPath() + "_" + id
                     ),
                     null,
-                    profile.equals(AgeGenerationProfiles.STANDARD)
-                            ? new AgeTraits(
-                                    AgeTraits.BiomeDistribution.SINGLE,
-                                    AgeTraits.Lighting.NORMAL,
-                                    AgeTraits.Weather.NORMAL,
-                                    1.0D,
-                                    0.0F,
-                                    0.0F
-                            )
-                            : AgeTraits.select(id.getMostSignificantBits())
+                    traits
             );
             var level = AgeDimensionService.ensureLoaded(helper.getLevel().getServer(), definition);
             helper.assertTrue(level != null, "The " + profile + " profile must load a runtime dimension");
@@ -192,6 +203,21 @@ public final class LinkingGameTests {
                         "Single Biome Distribution must expose exactly one biome"
                 );
             }
+            if (profile.equals(AgeGenerationProfiles.AMPLIFIED)) {
+                var biomeSource = level.getChunkSource().getGenerator().getBiomeSource();
+                helper.assertValueEqual(
+                        biomeSource.possibleBiomes().size(),
+                        2,
+                        "Tiled Biome Distribution must expose exactly two seeded biomes"
+                );
+                var origin = biomeSource.getNoiseBiome(0, 0, 0, null);
+                var eastTile = biomeSource.getNoiseBiome(64, 0, 0, null);
+                var diagonalTile = biomeSource.getNoiseBiome(64, 0, 64, null);
+                helper.assertFalse(origin.equals(eastTile),
+                        "Adjacent 256-block Tiled squares must alternate biomes");
+                helper.assertTrue(origin.equals(diagonalTile),
+                        "Diagonal 256-block Tiled squares must repeat the biome");
+            }
             if (definition.traits().lighting() == AgeTraits.Lighting.DARK) {
                 helper.assertFalse(level.dimensionType().hasSkyLight(),
                         "Dark Lighting Ages must suppress dimension skylight");