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glk |
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// vr-lite.diderot
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//
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// simple diffuse-only volume rendering with head-light, with an
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// opacity function that varies linearly between two values
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//
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input string dataFile; // name of dataset
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input real stepSz = 0.1; // size of steps
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input vec3 eye; // location of eye point
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input vec3 orig; // location of pixel (0,0)
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input vec3 cVec; // vector between pixels horizontally
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input vec3 rVec; // vector between pixels vertically
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input real valOpacMin; // highest value with opacity 0.0
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input real valOpacMax; // lowest value with opacity 1.0
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glk |
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// valOpacMin,Max pairs for sample datasets:
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// txs.nrrd 0.15, 0.35
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// vfrhand-nohip.nhdr, for skin: 200, 500
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// vfrhand-nohip.nhdr, for bone: 1330, 1630
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glk |
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image(3)[] img = load (dataFile);
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//field#1(3)[] F = convolve (bspln3, img);
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field#2(3)[] F = img ⊛ bspln3;
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actor RayCast (int row, int col)
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{
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vec3 pos = orig + real(row)*rVec + real(col)*cVec;
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vec3 dir = (pos - eye)/|pos - eye|;
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real t = 0.0;
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real transp = 1.0;
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real gray = 0.0;
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output vec4 rgba = [0.0, 0.0, 0.0, 0.0];
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update
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{
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pos = pos + stepSz*dir;
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if (inside (pos,F)) {
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real val = F@pos;
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vec3 grad = (∇ F)@pos;
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vec3 norm = -grad/|grad|;
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if (val > valOpacMin) { // we have some opacity
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real opac = 0.0; // dummy initialization
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if (val > valOpacMax) {
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opac = 1.0;
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} else {
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opac = (val - valOpacMin)/(valOpacMax - valOpacMin);
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}
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gray = gray + transp*opac*max(0.0, dot(-dir,norm));
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transp = transp*(1.0 - opac);
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}
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}
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if (transp < 0.01) { // early ray termination
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transp = 0.0;
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stabilize;
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}
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if (t > 40.0) {
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stabilize;
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}
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t = t + stepSz;
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}
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stabilize {
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rgba = [gray, gray, gray, 1.0-transp];
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}
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glk |
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/* render: output rgba */
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}
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initially [ RayCast(r, c) | r in 0..199, c in 0..199 ];
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