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<title>Simple VR example in Diderot</title>
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<h2 align="center">The Diderot Project</h2>
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<h3>A simple volume renderer in Diderot</h3>
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<p>
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The following code is a simple diffuse-only volume rendering with head-light
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written in Diderot.
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It uses an opacity function that varies linearly between two values.
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This example illustrates the use of probing both a field and its gradient.
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</p>
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<div align="center">
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<div align="left" class="code-display"><span class="code-type">input</span> <span class="code-type">string</span> dataFile; <span class="code-comment">// name of dataset</span>
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<span class="code-type">input</span> <span class="code-type">real</span> stepSz = 0.1; <span class="code-comment">// size of steps</span>
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<span class="code-type">input</span> <span class="code-type">vec3</span> eye; <span class="code-comment">// location of eye point</span>
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<span class="code-type">input</span> <span class="code-type">vec3</span> orig; <span class="code-comment">// location of pixel (0,0)</span>
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<span class="code-type">input</span> <span class="code-type">vec3</span> cVec; <span class="code-comment">// vector between pixels horizontally</span>
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<span class="code-type">input</span> <span class="code-type">vec3</span> rVec; <span class="code-comment">// vector between pixels vertically</span>
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<span class="code-type">input</span> <span class="code-type">real</span> valOpacMin; <span class="code-comment">// highest value with opacity 0.0</span>
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<span class="code-type">input</span> <span class="code-type">real</span> valOpacMax; <span class="code-comment">// lowest value with opacity 1.0 </span>
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<span class="code-type">image(3)[]</span> img = load (dataFile);
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<span class="code-type">field#1(3)[]</span> F = img ⊛ bspln3;
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<span class="code-kw">actor</span> RayCast (<span class="code-type">int</span> row, <span class="code-type">int</span> col)
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{
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<span class="code-type">vec3</span> pos = orig + <span class="code-type">real</span>(row)*rVec + <span class="code-type">real</span>(col)*cVec;
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<span class="code-type">vec3</span> dir = (pos - eye)/|pos - eye|;
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<span class="code-type">real</span> t = 0.0;
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<span class="code-type">real</span> transp = 1.0;
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<span class="code-type">real</span> gray = 0.0;
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<span class="code-type">output</span> <span class="code-type">vec4</span> rgba = [0.0, 0.0, 0.0, 0.0];
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<span class="code-kw">update</span> {
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pos = pos + stepSz*dir;
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<span class="code-kw">if</span> (inside (pos,F)) {
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<span class="code-type">real</span> val = F@pos;
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<span class="code-type">vec3</span> grad = ∇F@pos;
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<span class="code-type">vec3</span> norm = -grad / |grad|;
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<span class="code-kw">if</span> (val > valOpacMin) { <span class="code-comment">// we have some opacity </span>
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<span class="code-type">real</span> opac =
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1.0 <span class="code-kw">if</span> (val > valOpacMax)
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<span class="code-kw">else</span> (val - valOpacMin)/(valOpacMax - valOpacMin);
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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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<span class="code-kw">if</span> (transp < 0.01) { <span class="code-comment">// early ray termination</span>
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transp = 0.0;
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<span class="code-kw">stabilize</span>;
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}
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<span class="code-kw">if</span> (t > 40.0) {
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<span class="code-kw">stabilize</span>;
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}
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t = t + stepSz;
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}
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<span class="code-kw">stabilize</span> {
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rgba = [gray, gray, gray, 1.0-transp];
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}
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}
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<span class="code-kw">initially</span> [ RayCast(r, c) | r in 0..199, c in 0..199 ];
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</div>
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</div>
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<hr />
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Last modified: October 13, 2010.
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</body>
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