int ires=200;
field#2(3)[3,3] V= c4hexic ⊛ image("slab-c4h-ten9-small.nrrd");

strand raycast(int ui, int vi) {
tensor[3,3] F=V([ui,vi,1]);
real d=F[1,0];
real e=F[1,1];
real f=F[1,2];
real g=F[2,0];
real h=F[2,1];
real i=F[2,2];

output real out=(F[0,0]*(e*i- f*g))-(F[0,1]*(d*i-f*g))+(F[0,1]*(d*h-e*g));

  update {

      stabilize;
    }
}
initially [ raycast(ui, vi) | vi in 0..ires-1, ui in 0..ires-1 ];