cg learning - Serbipunk/notes GitHub Wiki
.obj file
V is Vertex.
VN is Vertex Normal.
VT is Vertex Texture Coordinate.
F represents a face/polygon,
and each overall vertice within it is declared in the order of
APreviouslyDefinedVertexIndex / APreviouslyDefinedTexCoordIndex / APreviouslyDefinedNormalIndex
(as in Vertex/TexCoord/Normal, or V/VT/VN.)
https://www.reddit.com/r/opengl/comments/6dn96r/reformatting_obj_file_vt_meaning/