Bit i set = splat layer i can grow trees.
Grid spacing in meters (≈ average distance between trees at weight 1).
Trees pack (and draw) out to this camera distance.
Instances beyond this distance (from the pack center) go to the far-LOD record set (drawn with the impostor mesh).
World-generation seed folded into the per-cell hash.
Authored tree settings (mirrors the Terrain component's tree fields).