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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>pbrt: emission.cpp Source File</title>
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<h1>emission.cpp</h1><a href="emission_8cpp.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001
<a name="l00002"></a>00002 <span class="comment">/*</span>
<a name="l00003"></a>00003 <span class="comment"> pbrt source code Copyright(c) 1998-2007 Matt Pharr and Greg Humphreys.</span>
<a name="l00004"></a>00004 <span class="comment"></span>
<a name="l00005"></a>00005 <span class="comment"> This file is part of pbrt.</span>
<a name="l00006"></a>00006 <span class="comment"></span>
<a name="l00007"></a>00007 <span class="comment"> pbrt is free software; you can redistribute it and/or modify</span>
<a name="l00008"></a>00008 <span class="comment"> it under the terms of the GNU General Public License as published by</span>
<a name="l00009"></a>00009 <span class="comment"> the Free Software Foundation; either version 2 of the License, or</span>
<a name="l00010"></a>00010 <span class="comment"> (at your option) any later version. Note that the text contents of</span>
<a name="l00011"></a>00011 <span class="comment"> the book "Physically Based Rendering" are *not* licensed under the</span>
<a name="l00012"></a>00012 <span class="comment"> GNU GPL.</span>
<a name="l00013"></a>00013 <span class="comment"></span>
<a name="l00014"></a>00014 <span class="comment"> pbrt is distributed in the hope that it will be useful,</span>
<a name="l00015"></a>00015 <span class="comment"> but WITHOUT ANY WARRANTY; without even the implied warranty of</span>
<a name="l00016"></a>00016 <span class="comment"> MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the</span>
<a name="l00017"></a>00017 <span class="comment"> GNU General Public License for more details.</span>
<a name="l00018"></a>00018 <span class="comment"></span>
<a name="l00019"></a>00019 <span class="comment"> You should have received a copy of the GNU General Public License</span>
<a name="l00020"></a>00020 <span class="comment"> along with this program. If not, see <http://www.gnu.org/licenses/>.</span>
<a name="l00021"></a>00021 <span class="comment"></span>
<a name="l00022"></a>00022 <span class="comment"> */</span>
<a name="l00023"></a>00023
<a name="l00024"></a>00024 <span class="comment">// emission.cpp*</span>
<a name="l00025"></a>00025 <span class="preprocessor">#include "<a class="code" href="volume_8h.html">volume.h</a>"</span>
<a name="l00026"></a>00026 <span class="preprocessor">#include "<a class="code" href="transport_8h.html">transport.h</a>"</span>
<a name="l00027"></a>00027 <span class="preprocessor">#include "<a class="code" href="scene_8h.html">scene.h</a>"</span>
<a name="l00028"></a>00028 <span class="comment">// EmissionIntegrator Declarations</span>
<a name="l00029"></a><a class="code" href="classEmissionIntegrator.html">00029</a> <span class="keyword">class </span><a class="code" href="classEmissionIntegrator.html">EmissionIntegrator</a> : <span class="keyword">public</span> <a class="code" href="classVolumeIntegrator.html">VolumeIntegrator</a> {
<a name="l00030"></a>00030 <span class="keyword">public</span>:
<a name="l00031"></a>00031 <span class="comment">// EmissionIntegrator Public Methods</span>
<a name="l00032"></a><a class="code" href="classEmissionIntegrator.html#a83b67ea9a3d0e3a4bc90664c47eb343">00032</a> <a class="code" href="classEmissionIntegrator.html#a83b67ea9a3d0e3a4bc90664c47eb343">EmissionIntegrator</a>(<span class="keywordtype">float</span> ss) { <a class="code" href="classEmissionIntegrator.html#578aaee19d712d33a9394f5487a0191e">stepSize</a> = ss; }
<a name="l00033"></a>00033 <span class="keywordtype">void</span> <a class="code" href="classEmissionIntegrator.html#b465eb9aadb2abd5672501cc9152d368">RequestSamples</a>(<a class="code" href="structSample.html">Sample</a> *sample, <span class="keyword">const</span> <a class="code" href="classScene.html">Scene</a> *scene);
<a name="l00034"></a>00034 <a class="code" href="classSpectrum.html">Spectrum</a> <a class="code" href="classEmissionIntegrator.html#20eedda00f9c1ac0c5a311a077f6e900">Transmittance</a>(<span class="keyword">const</span> <a class="code" href="classScene.html">Scene</a> *, <span class="keyword">const</span> <a class="code" href="classRay.html">Ray</a> &ray, <span class="keyword">const</span> <a class="code" href="structSample.html">Sample</a> *sample, <span class="keywordtype">float</span> *alpha) <span class="keyword">const</span>;
<a name="l00035"></a>00035 <a class="code" href="classSpectrum.html">Spectrum</a> <a class="code" href="classEmissionIntegrator.html#e189bd9e549c7fb5f60a999eae3a1162">Li</a>(<span class="keyword">const</span> <a class="code" href="classScene.html">Scene</a> *, <span class="keyword">const</span> <a class="code" href="classRayDifferential.html">RayDifferential</a> &ray, <span class="keyword">const</span> <a class="code" href="structSample.html">Sample</a> *sample, <span class="keywordtype">float</span> *alpha) <span class="keyword">const</span>;
<a name="l00036"></a>00036 <span class="keyword">private</span>:
<a name="l00037"></a>00037 <span class="comment">// EmissionIntegrator Private Data</span>
<a name="l00038"></a><a class="code" href="classEmissionIntegrator.html#578aaee19d712d33a9394f5487a0191e">00038</a> <span class="keywordtype">float</span> <a class="code" href="classEmissionIntegrator.html#578aaee19d712d33a9394f5487a0191e">stepSize</a>;
<a name="l00039"></a><a class="code" href="classEmissionIntegrator.html#00bed366532c8b2d66cf8bc8c850034b">00039</a> <span class="keywordtype">int</span> <a class="code" href="classEmissionIntegrator.html#00bed366532c8b2d66cf8bc8c850034b">tauSampleOffset</a>, <a class="code" href="classEmissionIntegrator.html#babd46bc5639118f011350e8e51ed8c0">scatterSampleOffset</a>;
<a name="l00040"></a>00040 };
<a name="l00041"></a>00041 <span class="comment">// EmissionIntegrator Method Definitions</span>
<a name="l00042"></a><a class="code" href="classEmissionIntegrator.html#b465eb9aadb2abd5672501cc9152d368">00042</a> <span class="keywordtype">void</span> <a class="code" href="classEmissionIntegrator.html#b465eb9aadb2abd5672501cc9152d368">EmissionIntegrator::RequestSamples</a>(<a class="code" href="structSample.html">Sample</a> *sample,
<a name="l00043"></a>00043 <span class="keyword">const</span> <a class="code" href="classScene.html">Scene</a> *scene) {
<a name="l00044"></a>00044 <a class="code" href="classEmissionIntegrator.html#00bed366532c8b2d66cf8bc8c850034b">tauSampleOffset</a> = sample-><a class="code" href="structSample.html#a2b567c5a4160488ba81953b59df59f0">Add1D</a>(1);
<a name="l00045"></a>00045 <a class="code" href="classEmissionIntegrator.html#babd46bc5639118f011350e8e51ed8c0">scatterSampleOffset</a> = sample-><a class="code" href="structSample.html#a2b567c5a4160488ba81953b59df59f0">Add1D</a>(1);
<a name="l00046"></a>00046 }
<a name="l00047"></a>00047 <a class="code" href="classSpectrum.html">Spectrum</a>
<a name="l00048"></a><a class="code" href="classEmissionIntegrator.html#20eedda00f9c1ac0c5a311a077f6e900">00048</a> <a class="code" href="classEmissionIntegrator.html#20eedda00f9c1ac0c5a311a077f6e900">EmissionIntegrator::Transmittance</a>(<span class="keyword">const</span> <a class="code" href="classScene.html">Scene</a> *scene,
<a name="l00049"></a>00049 <span class="keyword">const</span> <a class="code" href="classRay.html">Ray</a> &ray, <span class="keyword">const</span> <a class="code" href="structSample.html">Sample</a> *sample,
<a name="l00050"></a>00050 <span class="keywordtype">float</span> *alpha)<span class="keyword"> const </span>{
<a name="l00051"></a>00051 <span class="keywordflow">if</span> (!scene-><a class="code" href="classScene.html#326823a326e0a99b2e9325f96d942355">volumeRegion</a>) <span class="keywordflow">return</span> <a class="code" href="classSpectrum.html">Spectrum</a>(1.f);
<a name="l00052"></a>00052 <span class="keywordtype">float</span> step = sample ? <a class="code" href="classEmissionIntegrator.html#578aaee19d712d33a9394f5487a0191e">stepSize</a> : 4.f * <a class="code" href="classEmissionIntegrator.html#578aaee19d712d33a9394f5487a0191e">stepSize</a>;
<a name="l00053"></a>00053 <span class="keywordtype">float</span> offset =
<a name="l00054"></a>00054 sample ? sample-><a class="code" href="structSample.html#4a1ae5fbae61678e57efaf185a319ceb">oneD</a>[<a class="code" href="classEmissionIntegrator.html#00bed366532c8b2d66cf8bc8c850034b">tauSampleOffset</a>][0] :
<a name="l00055"></a>00055 <a class="code" href="pbrt_8h.html#4f11994534b888fcf650c04b5d61d9d4">RandomFloat</a>();
<a name="l00056"></a>00056 <a class="code" href="classSpectrum.html">Spectrum</a> tau =
<a name="l00057"></a>00057 scene-><a class="code" href="classScene.html#326823a326e0a99b2e9325f96d942355">volumeRegion</a>-><a class="code" href="classVolumeRegion.html#4be8cab8f7516b69c45c8858903d4bdf">Tau</a>(ray, step, offset);
<a name="l00058"></a>00058 <span class="keywordflow">return</span> Exp(-tau);
<a name="l00059"></a>00059 }
<a name="l00060"></a><a class="code" href="classEmissionIntegrator.html#e189bd9e549c7fb5f60a999eae3a1162">00060</a> <a class="code" href="classSpectrum.html">Spectrum</a> <a class="code" href="classEmissionIntegrator.html#e189bd9e549c7fb5f60a999eae3a1162">EmissionIntegrator::Li</a>(<span class="keyword">const</span> <a class="code" href="classScene.html">Scene</a> *scene,
<a name="l00061"></a>00061 <span class="keyword">const</span> <a class="code" href="classRayDifferential.html">RayDifferential</a> &ray, <span class="keyword">const</span> <a class="code" href="structSample.html">Sample</a> *sample,
<a name="l00062"></a>00062 <span class="keywordtype">float</span> *alpha)<span class="keyword"> const </span>{
<a name="l00063"></a>00063 <a class="code" href="classVolumeRegion.html">VolumeRegion</a> *vr = scene-><a class="code" href="classScene.html#326823a326e0a99b2e9325f96d942355">volumeRegion</a>;
<a name="l00064"></a>00064 <span class="keywordtype">float</span> t0, t1;
<a name="l00065"></a>00065 <span class="keywordflow">if</span> (!vr || !vr-><a class="code" href="classVolumeRegion.html#55e67282f25b5c58632c824f597818dd">IntersectP</a>(ray, &t0, &t1)) <span class="keywordflow">return</span> 0.f;
<a name="l00066"></a>00066 <span class="comment">// Do emission-only volume integration in _vr_</span>
<a name="l00067"></a>00067 <a class="code" href="classSpectrum.html">Spectrum</a> Lv(0.);
<a name="l00068"></a>00068 <span class="comment">// Prepare for volume integration stepping</span>
<a name="l00069"></a>00069 <span class="keywordtype">int</span> <a class="code" href="util_8cpp.html#0240ac851181b84ac374872dc5434ee4">N</a> = <a class="code" href="pbrt_8h.html#1a941973fe233e9e8179a48dff4115c8">Ceil2Int</a>((t1-t0) / <a class="code" href="classEmissionIntegrator.html#578aaee19d712d33a9394f5487a0191e">stepSize</a>);
<a name="l00070"></a>00070 <span class="keywordtype">float</span> step = (t1 - t0) / N;
<a name="l00071"></a>00071 <a class="code" href="classSpectrum.html">Spectrum</a> Tr(1.f);
<a name="l00072"></a>00072 <a class="code" href="classPoint.html">Point</a> p = ray(t0), pPrev;
<a name="l00073"></a>00073 <a class="code" href="classVector.html">Vector</a> w = -ray.<a class="code" href="classRay.html#5bbfc94e178e0a050b51200acc579069">d</a>;
<a name="l00074"></a>00074 <span class="keywordflow">if</span> (sample)
<a name="l00075"></a>00075 t0 += sample-><a class="code" href="structSample.html#4a1ae5fbae61678e57efaf185a319ceb">oneD</a>[<a class="code" href="classEmissionIntegrator.html#babd46bc5639118f011350e8e51ed8c0">scatterSampleOffset</a>][0] * step;
<a name="l00076"></a>00076 <span class="keywordflow">else</span>
<a name="l00077"></a>00077 t0 += <a class="code" href="pbrt_8h.html#4f11994534b888fcf650c04b5d61d9d4">RandomFloat</a>() * step;
<a name="l00078"></a>00078 <span class="keywordflow">for</span> (<span class="keywordtype">int</span> i = 0; i < N; ++i, t0 += step) {
<a name="l00079"></a>00079 <span class="comment">// Advance to sample at _t0_ and update _T_</span>
<a name="l00080"></a>00080 pPrev = p;
<a name="l00081"></a>00081 p = ray(t0);
<a name="l00082"></a>00082 <a class="code" href="classSpectrum.html">Spectrum</a> stepTau = vr-><a class="code" href="classVolumeRegion.html#4be8cab8f7516b69c45c8858903d4bdf">Tau</a>(<a class="code" href="classRay.html">Ray</a>(pPrev, p - pPrev, 0, 1),
<a name="l00083"></a>00083 .5f * <a class="code" href="classEmissionIntegrator.html#578aaee19d712d33a9394f5487a0191e">stepSize</a>, <a class="code" href="pbrt_8h.html#4f11994534b888fcf650c04b5d61d9d4">RandomFloat</a>());
<a name="l00084"></a>00084 Tr *= Exp(-stepTau);
<a name="l00085"></a>00085 <span class="comment">// Possibly terminate raymarching if transmittance is small</span>
<a name="l00086"></a>00086 <span class="keywordflow">if</span> (Tr.<a class="code" href="classSpectrum.html#25d4cb8d137b7bb0f85e636ea41461a8">y</a>() < 1e-3) {
<a name="l00087"></a>00087 <span class="keyword">const</span> <span class="keywordtype">float</span> continueProb = .5f;
<a name="l00088"></a>00088 <span class="keywordflow">if</span> (<a class="code" href="pbrt_8h.html#4f11994534b888fcf650c04b5d61d9d4">RandomFloat</a>() > continueProb) <span class="keywordflow">break</span>;
<a name="l00089"></a>00089 Tr /= continueProb;
<a name="l00090"></a>00090 }
<a name="l00091"></a>00091 <span class="comment">// Compute emission-only source term at _p_</span>
<a name="l00092"></a>00092 Lv += Tr * vr-><a class="code" href="classVolumeRegion.html#204a4159db9cf97002a98ff65725d557">Lve</a>(p, w);
<a name="l00093"></a>00093 }
<a name="l00094"></a>00094 <span class="keywordflow">return</span> Lv * step;
<a name="l00095"></a>00095 }
<a name="l00096"></a><a class="code" href="emission_8cpp.html#53ba186b32690142f1807bb0f1a16342">00096</a> <span class="keyword">extern</span> <span class="stringliteral">"C"</span> <a class="code" href="pbrt_8h.html#808e08638be3cba36e36759e5b150de0">DLLEXPORT</a> <a class="code" href="classVolumeIntegrator.html">VolumeIntegrator</a> *<a class="code" href="emission_8cpp.html#53ba186b32690142f1807bb0f1a16342">CreateVolumeIntegrator</a>(<span class="keyword">const</span> <a class="code" href="classParamSet.html">ParamSet</a> &params) {
<a name="l00097"></a>00097 <span class="keywordtype">float</span> <a class="code" href="classEmissionIntegrator.html#578aaee19d712d33a9394f5487a0191e">stepSize</a> = params.<a class="code" href="classParamSet.html#87143fd8e73a75082179a110d42531a4">FindOneFloat</a>(<span class="stringliteral">"stepsize"</span>, 1.f);
<a name="l00098"></a>00098 <span class="keywordflow">return</span> <span class="keyword">new</span> <a class="code" href="classEmissionIntegrator.html#a83b67ea9a3d0e3a4bc90664c47eb343">EmissionIntegrator</a>(stepSize);
<a name="l00099"></a>00099 }
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