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