mtllib cube_usemtl.mtl
 
g cube
 
v  0.0  0.0  0.0
v  0.0  0.0  1.0
v  0.0  1.0  0.0
v  0.0  1.0  1.0
v  1.0  0.0  0.0
v  1.0  0.0  1.0
v  1.0  1.0  0.0
v  1.0  1.0  1.0

vn  0.0  0.0  1.0
vn  0.0  0.0 -1.0
vn  0.0  1.0  0.0
vn  0.0 -1.0  0.0
vn  1.0  0.0  0.0
vn -1.0  0.0  0.0

usemtl mtl3
f  1//2  7//2  5//2
usemtl mtl3
f  1//2  3//2  7//2 
usemtl mtl
f  1//6  4//6  3//6 
usemtl mtl
f  1//6  2//6  4//6 
usemtl mtl
f  3//3  8//3  7//3 
usemtl mtl2
f  3//3  4//3  8//3 
usemtl mtl2
f  5//5  7//5  8//5 
usemtl mtl2
f  5//5  8//5  6//5 
usemtl mtl2
f  1//4  5//4  6//4 
usemtl mtl
f  1//4  6//4  2//4 
usemtl mtl
f  2//1  6//1  8//1 
usemtl mtl
f  2//1  8//1  4//1