ReadonlygroupThe geometry group, or -1 when the mesh has one material (draw range only).
ReadonlyinstanceThe instance of an InstancedMesh or BatchedMesh, or -1 for a plain mesh.
ReadonlymaterialThe group's materialIndex into the mesh's array of materials, or -1.
ReadonlythreeThe three material that draws these triangles (the group's, or the mesh's).
What BvhSceneFromObject3DOptions.material is told about the instance it names a material for.