I want my custom mob to spawn high in the sky (like at y-level 192), as it's supposed to be a flying mob. I've noticed that my mob is able to spawn in the air, but only nearby solid blocks at the y-level where I want it to spawn.

Here is my code below that listens to the SpawnPlacementRegisterEvent:

@SubscribeEvent
public static void onSpawnPlacementRegisterEvent(SpawnPlacementRegisterEvent event) {
    event.register(ModEntityTypes.CUSTOM_MOB.get(),
            SpawnPlacements.Type.NO_RESTRICTIONS, Heightmap.Types.MOTION_BLOCKING_NO_LEAVES,
            CustomMob::checkCustomMobSpawnRules, SpawnPlacementRegisterEvent.Operation.OR);
}
// (CustomMob::checkCustomMobSpawnRules checks if the BlockPos is in the air)

Edited April 1, 20232 yr by LeeCrafts

First you are telling it to spawn on top of blocks that are not leaves "Heightmap.Types.MOTION_BLOCKING_NO_LEAVES".

 

But I don't think spawning in the air is possible for natural spawns.

Even if you wrote your own HeightMap.Types, the code is hardwired to ignore BlockState.isAir().

e.g. see NaturalSpawner.getTopNonCollidingPos() which determines the y location of spawns.

 

In vanilla. flying mobs naturally spawn on the ground. e.g. "slabbing your nether" stops ghast spawns.

It's only mob spawners or hardwired things like the dragon fight that can spawn in the air.

In that case, I guess I would have to manually implement the spawning mechanics (e.g. by subscribing to LivingTickEvent). Thank you for your help. 👍