// vr.diderot
//
// volume rendering example in Diderot
//

input string dataFile;		// name of dataset
input real stepSz;		// size of steps
input vec<3> light;
input int wid = 640;
input int ht = 480;

image[3] img = image (dataFile);

field#1(3)[3] F = bspln3 ⊛ img;
 
strand RayCast (int row, int col)
{
    vec<3>	dir = (real(row), real(col), 0.0);
    vec<3>	pos = (0.0, 0.0, 0.0);
    real	t = 0.0;
    real[4]	color = (0.0, 0.0, 0.0, 0.0);	

    update
    {
	vec<3> pt = pos + t*dir;
	t = t + stepSz;
	vec<3> g = (D F)(pt);
	color = over(color, phong(light, g, txf(F(pt))));
	if (color[3] >= 0.999)
	    stabilize;
    }

}

initially
  [ RayCast(r, c) | r in 0 .. ht-1, c in 0 .. wid-1 ];