mtllib window.mtl
usemtl window
v -1 -1 0
v 1 -1 0
v -1 1 0
v 1 1 0
vt 0 0
vt 1 0
vt 0 1
vt 1 1
f 1/1 2/2 3/3
f 4/4 3/3 2/2