// vr-MIP.diderot
//
// maximum intensity projection in Diderot
//

input string dataFile;		// name of dataset
input real stepSz = 0.1;	// size of steps
				// e.g. 0.1
input vec3 eye;			// location of eye point
				// e.g. txs: (25,15,10)
                                //      vox1,x: (-8,2,2)
                                //      vox1,y: (2,-8,2)
                                //      vox1,z: (2,2,-8)
input vec3 orig;		// location of pixel (0,0)
				// e.g. txs: (8.83877,2.5911,7.65275)  
				//      vox1,x: (0,3.4036,3.4036)
				//      vox1,y: (0.596402,0,3.4036)
				//      vox1,z: (3.4036,3.4036,0)
input vec3 cVec;		// vector between pixels horizontally
				// e.g. txs: (-0.0151831,0.0278357,0)
				//      vox1,x: (0,-0.014036,0)
				//      vox1,y: (0.014036,0,0)
				//      vox1,z: (-0.014036,0,0)
input vec3 rVec;		// vector between pixels vertically
				// e.g. txs: (0.0074887,0.00408474,-0.0305383)
				//      vox1,x: (0,0,-0.014036)
				//      vox1,y: (0,0,-0.014036)
				//      vox1,z: (0,-0.014036,0)

image(3)[] img = load (dataFile);

//field#1(3)[] F = convolve (bspln3, img);
field#2(3)[] F = convolve (bspln3, img);

actor RayCast (int row, int col)
{
    vec3 pos = orig + real(row)*rVec + real(col)*cVec;
    vec3 dir = (pos - eye)/|pos - eye|;
    real t = 0.0;
    output real maxval = -inf; 

    update
    {
        pos = pos + stepSz*dir;
        if (inside (pos,F)) {
	  real val = F@pos;
	  maxval = max(val, maxval);
	}
        if (t > 20.0)
            stabilize;
        t = t + stepSz;
    }

    /* render: output maxval */
}

initially [ RayCast(r, c) | r in 0..199, c in 0..199 ];