Overlay biome mob spawns

- 26.3 custom biomes write natural_mob_spawns as an overlay modifier with its argument, matching vanilla biomes
- NeoForge biome modifiers can add spawns to Iris biomes again
- The 26.3 custom biome codec test checks the overlay modifier
This commit is contained in:
Brian Neumann-Fopiano
2026-09-29 03:56:40 -04:00
parent 6fd877ebfc
commit 5e95248057
2 changed files with 8 additions and 2 deletions
@@ -13,6 +13,7 @@ import net.minecraft.data.registries.VanillaRegistries;
import net.minecraft.resources.RegistryOps;
import net.minecraft.server.Bootstrap;
import net.minecraft.world.attribute.EnvironmentAttributes;
import net.minecraft.world.attribute.modifier.MobSpawnSettingsModifier;
import net.minecraft.world.entity.MobCategory;
import net.minecraft.world.level.biome.Biome;
import net.minecraft.world.level.biome.MobSpawnSettings;
@@ -53,5 +54,7 @@ public class CustomBiomeCodecTest {
assertEquals(2, decoded.count().minInclusive());
assertEquals(4, decoded.count().maxInclusive());
assertEquals(0x102030, biome.getWaterColor() & 0xFFFFFF);
assertEquals(MobSpawnSettingsModifier.overlay(),
biome.getAttributes().get(EnvironmentAttributes.NATURAL_MOB_SPAWNS).modifier());
}
}
@@ -34,9 +34,12 @@ public final class DataFixerV263 extends DataFixerV1217 {
.put("max_inclusive", maximum));
}
}
// Vanilla writes spawns as an overlay. A bare value decodes as an override, which NeoForge biome modifiers refuse to edit.
attributes.put("minecraft:gameplay/natural_mob_spawns", new JSONObject()
.put("spawns_by_category", spawners)
.put("spawn_costs", fixed.getJSONObject("spawn_costs")));
.put("argument", new JSONObject()
.put("spawns_by_category", spawners)
.put("spawn_costs", fixed.getJSONObject("spawn_costs")))
.put("modifier", "overlay"));
Object probability = fixed.remove("creature_spawn_probability");
if (probability != null) {
attributes.put("minecraft:gameplay/creature_world_gen_spawn_probability", probability);