mtllib basis.mtl
v 0 0 0
v 1 0 0
v 0 1 0
v 0 0 1
v 2 0 0
v 0 2 0
v 0 0 2
v 2.1 0 0
v 0 2.1 0
v 0 0 2.1
usemtl x
f 1 2 3
l 1 5
p 8
usemtl y
f 1 3 4
l 1 6
p 9
usemtl z
f 1 4 2
l 1 7
p 10