x 0 1/4 a
-x+1/2 0 3/4 a
1/4 y 0 b
1/4 -y 1/2 b
0 1/4 z c
0 3/4 -z+1/2 c
x y z d
-x+1/2 -y z+1/2 d
-x y+1/2 -z+1/2 d
x+1/2 -y+1/2 -z d