v -0.5 0 -0.5
v  0.5 0  0.5
v  0.5 0 -0.5
v -0.5 0  0.5

vt 0 0
vt 1 1
vt 1 0
vt 0 1

f 1/1 2/2 3/3
f 1/1 4/4 2/2