I have a feature that I want to spawn only in specific chunk coordinates. The way the coordinates are determined is a little complicated, but I have a function f(chunkX, chunkZ, seed) that determines whether the feature is allowed to spawn, without any reference to world information, just the coordinates. For the sake of example, suppose I want to spawn the feature only in chunks where the X coordinate is equal to the Z coordinate.

My current solution is to create a subclass of PlacementFilter, which for the example I gave would look like

    protected boolean shouldPlace(PlacementContext context, RandomSource rand, BlockPos pos) {
        //return true if ChunkPos(pos) has the same X and Z
    }

This then goes in the List of PlacementModifiers for the PlacedFeature. This approach works, in that it generates correctly in the intended chunks and not at all in the other chunks.

However, I am concerned that this approach may cause issues, as I don't think it will "intelligently" apply the filter, and instead re-check for each instance in the chunk. If I am trying to generate the feature 100 times in the chunks it is supposed to be in, I suspect it will also pick out 100 positions in every other chunk and try to generate them there before getting individually filtered by my PlacementFilter. This could become a significant waste of resources if I have many such features.

Is there a better way to have a feature only spawn in a small minority of chunks, based only on chunk coordinates and seed (not contents)?

6 hours ago, fweo said:

Is there a better way to have a feature only spawn in a small minority of chunks, based only on chunk coordinates and seed (not contents)?

You're making a PlacementModifier correct? Regardless of what you choose to do with the feature, it will attempt to generate for every chunk. The placement modifier determines which block positions to apply your feature at within the chunk. So, if you return an empty stream, your feature won't be applied in the chunk. If you return a stream of one or more positions, it will attempt to apply the feature at those positions.