Optional Readonlyprimitivethree-mesh-bvh's primitiveLimit: the walk down a mesh's tree stops at
the first node with fewer triangles than this (or at a leaf), and that
subtree becomes one top-level leaf. Default
DEFAULT_CLUSTER_PRIMITIVE_LIMIT (64). A positive integer, or
Infinity for no split (the scene comes back as it was).
Optional ReadonlysplitWhich records to cut into clusters; the others keep one leaf for their
whole mesh. Default: records whose mesh no other record traces
(sharedBy === 1), as ClusteredBVH references instanced meshes
whole. Leave out meshes you refit (deforming meshes): their cluster
copies don't follow a refit.
Optional ReadonlytopThe top level's SAH options (one cluster per leaf, as one instance per leaf).
Options of clusterTraceScene.