Occluder shape resource for use with occlusion culling in [OccluderInstance3D]. [Occluder3D] stores an occluder shape that can be used by the engine's occlusion culling system. See [OccluderInstance3D]'s documentation for instructions on setting up occlusion culling. $DOCS_URL/tutorials/3d/occlusion_culling.html Returns the occluder shape's vertex indices. Returns the occluder shape's vertex positions.