The problem with OBJ is, that you have to understand one thing: Vertex definitions as well as texture coordinates are global no matter where they are located in the file. They appear in groups sometimes but they aren't grouped...but: When referencing to a coodinate/vertex from a group's face definition list, you can only reference to vertices already defined. If their definition comes later in the file, you can't reference them. So they are global...but not completely. It would have been a much better idea IMHO to put them at the beginning of the file outside of any group instead of spreading them all over the file...and every exporter does it differently...ARGHH!