Documentation

A face is a triplet of indices. Face vi vti vni is a face that indexes the locations with vi, the texture coordinates with vti and the normals with vni. An index set to Nothing means no information. That is, if vni == Nothing, then that Face doesn’t have a normal associated with.

Keep in mind that Face doesn’t represent a polygonal face directly. It represents a face index, which is a triplet. In theory, a polygonal face is 3 Faces.