x, y, z, t, u, v, w, a, b, 
t*x-y*z
-u*y+v*x-v+y
t^2-w^2+z^2
-a^2+u^2+v^2-2*u+1
-b^2+t^2-2*t*v+u^2-2*u*z+v^2+z^2
