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