/*
				 * from blender-2.43/release/scripts/export_obj.py
				 * 
				 * mtllib = material library
				 * usemtl = material to use
				 * o      = objectname
				 * g      = group
				 * s      = smooth (<on/off>)
				 * v      = vertex (<x> <y> <z>)
				 * vn     = normal (<x> <y> <z>)
				 * vt     = uv (<x> <y> <z>)
				 * f      = face ((<vertex>/<uv>/<normal>)|(<vertex>//<normal>)|(<vertex>/<uv>)|(<vertex>))+ 
				 */