Obj 파일 parser 제작 가이드라인

Starting character / word	Meaning
#	Comment line
v	Defines  vertex points in 3D space, with coordinates of( x, y,z,w), w is optional
vt	Define   texture coordinates (u,v,w) where w is optional
vn	Defines normals (x,y,z)
f	Defines a face, composed of index of  vertex/texture/normal. Note that texture and normal is optional. If both texture and normal are absent f 1 2 3 If texture exists, but normal absent f 1/3  2/2  3/4 If texture is absent, but normal exists f 1//3  2//2  3//4 if all them exist f 1/2/3  2/3/2  3/2/4 each face can contains more than 3 elements
mtllib	Materials that describe the visual aspects of the polygons are stored in external .mtl files. The .mtl file may contain one or more named material definitions.
o	Object name
g	group name
usemtl	Defines a material to use, this material will continue to be used until another usemtl line (corresponding material is saved in .mtl file)
s	Smooth shading
mtllib	Point to an external .mtl file that saves the object materials

출처 : http://web.cse.ohio-state.edu/~hwshen/581/Site/Lab3_files/Labhelp_Obj_parser.htm