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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<h1>single.cpp</h1><a href="single_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">// single.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">// SingleScattering Declarations</span>
<a name="l00029"></a><a class="code" href="classSingleScattering.html">00029</a> <span class="keyword">class </span><a class="code" href="classSingleScattering.html">SingleScattering</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">// SingleScattering Public Methods</span>
<a name="l00032"></a><a class="code" href="classSingleScattering.html#4f0137f56ab4b93b53c6adaf2813d782">00032</a> <a class="code" href="classSingleScattering.html#4f0137f56ab4b93b53c6adaf2813d782">SingleScattering</a>(<span class="keywordtype">float</span> ss) { <a class="code" href="classSingleScattering.html#438fa6a0b44fab5f1da7df70a78430cd">stepSize</a> = ss; }
<a name="l00033"></a>00033 <a class="code" href="classSpectrum.html">Spectrum</a> <a class="code" href="classSingleScattering.html#b25fec434b992826021fc6623efbdb78">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,
<a name="l00034"></a>00034 <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 <span class="keywordtype">void</span> <a class="code" href="classSingleScattering.html#2c271bcebe461f263374b266b6d011ad">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="l00036"></a>00036 <a class="code" href="classSpectrum.html">Spectrum</a> <a class="code" href="classSingleScattering.html#8d37f7e96f4790b2ba53f984acb3cd4d">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="l00037"></a>00037 <span class="keyword">private</span>:
<a name="l00038"></a>00038 <span class="comment">// SingleScattering Private Data</span>
<a name="l00039"></a><a class="code" href="classSingleScattering.html#438fa6a0b44fab5f1da7df70a78430cd">00039</a> <span class="keywordtype">float</span> <a class="code" href="classSingleScattering.html#438fa6a0b44fab5f1da7df70a78430cd">stepSize</a>;
<a name="l00040"></a><a class="code" href="classSingleScattering.html#79fc999a7cd60971011370a9d4b99d14">00040</a> <span class="keywordtype">int</span> <a class="code" href="classSingleScattering.html#79fc999a7cd60971011370a9d4b99d14">tauSampleOffset</a>, <a class="code" href="classSingleScattering.html#c6efdeb8681eeb9533d9276b1b7bc1c9">scatterSampleOffset</a>;
<a name="l00041"></a>00041 };
<a name="l00042"></a>00042 <span class="comment">// SingleScattering Method Definitions</span>
<a name="l00043"></a><a class="code" href="classSingleScattering.html#2c271bcebe461f263374b266b6d011ad">00043</a> <span class="keywordtype">void</span> <a class="code" href="classSingleScattering.html#2c271bcebe461f263374b266b6d011ad">SingleScattering::RequestSamples</a>(<a class="code" href="structSample.html">Sample</a> *sample,
<a name="l00044"></a>00044 <span class="keyword">const</span> <a class="code" href="classScene.html">Scene</a> *scene) {
<a name="l00045"></a>00045 <a class="code" href="classSingleScattering.html#79fc999a7cd60971011370a9d4b99d14">tauSampleOffset</a> = sample-><a class="code" href="structSample.html#a2b567c5a4160488ba81953b59df59f0">Add1D</a>(1);
<a name="l00046"></a>00046 <a class="code" href="classSingleScattering.html#c6efdeb8681eeb9533d9276b1b7bc1c9">scatterSampleOffset</a> = sample-><a class="code" href="structSample.html#a2b567c5a4160488ba81953b59df59f0">Add1D</a>(1);
<a name="l00047"></a>00047 }
<a name="l00048"></a><a class="code" href="classSingleScattering.html#b25fec434b992826021fc6623efbdb78">00048</a> <a class="code" href="classSpectrum.html">Spectrum</a> <a class="code" href="classSingleScattering.html#b25fec434b992826021fc6623efbdb78">SingleScattering::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, <span class="keywordtype">float</span> *alpha)<span class="keyword"> const </span>{
<a name="l00050"></a>00050 <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="l00051"></a>00051 <span class="keywordtype">float</span> step = sample ? <a class="code" href="classSingleScattering.html#438fa6a0b44fab5f1da7df70a78430cd">stepSize</a> : 4.f * <a class="code" href="classSingleScattering.html#438fa6a0b44fab5f1da7df70a78430cd">stepSize</a>;
<a name="l00052"></a>00052 <span class="keywordtype">float</span> offset = sample ? sample-><a class="code" href="structSample.html#4a1ae5fbae61678e57efaf185a319ceb">oneD</a>[<a class="code" href="classSingleScattering.html#79fc999a7cd60971011370a9d4b99d14">tauSampleOffset</a>][0] :
<a name="l00053"></a>00053 <a class="code" href="pbrt_8h.html#4f11994534b888fcf650c04b5d61d9d4">RandomFloat</a>();
<a name="l00054"></a>00054 <a class="code" href="classSpectrum.html">Spectrum</a> tau = scene-><a class="code" href="classScene.html#326823a326e0a99b2e9325f96d942355">volumeRegion</a>-><a class="code" href="classVolumeRegion.html#4be8cab8f7516b69c45c8858903d4bdf">Tau</a>(ray, step, offset);
<a name="l00055"></a>00055 <span class="keywordflow">return</span> Exp(-tau);
<a name="l00056"></a>00056 }
<a name="l00057"></a><a class="code" href="classSingleScattering.html#8d37f7e96f4790b2ba53f984acb3cd4d">00057</a> <a class="code" href="classSpectrum.html">Spectrum</a> <a class="code" href="classSingleScattering.html#8d37f7e96f4790b2ba53f984acb3cd4d">SingleScattering::Li</a>(<span class="keyword">const</span> <a class="code" href="classScene.html">Scene</a> *scene,
<a name="l00058"></a>00058 <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="l00059"></a>00059 <span class="keywordtype">float</span> *alpha)<span class="keyword"> const </span>{
<a name="l00060"></a>00060 <a class="code" href="classVolumeRegion.html">VolumeRegion</a> *vr = scene-><a class="code" href="classScene.html#326823a326e0a99b2e9325f96d942355">volumeRegion</a>;
<a name="l00061"></a>00061 <span class="keywordtype">float</span> t0, t1;
<a name="l00062"></a>00062 <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="l00063"></a>00063 <span class="comment">// Do single scattering volume integration in _vr_</span>
<a name="l00064"></a>00064 <a class="code" href="classSpectrum.html">Spectrum</a> Lv(0.);
<a name="l00065"></a>00065 <span class="comment">// Prepare for volume integration stepping</span>
<a name="l00066"></a>00066 <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="classSingleScattering.html#438fa6a0b44fab5f1da7df70a78430cd">stepSize</a>);
<a name="l00067"></a>00067 <span class="keywordtype">float</span> step = (t1 - t0) / N;
<a name="l00068"></a>00068 <a class="code" href="classSpectrum.html">Spectrum</a> Tr(1.f);
<a name="l00069"></a>00069 <a class="code" href="classPoint.html">Point</a> p = ray(t0), pPrev;
<a name="l00070"></a>00070 <a class="code" href="classVector.html">Vector</a> w = -ray.<a class="code" href="classRay.html#5bbfc94e178e0a050b51200acc579069">d</a>;
<a name="l00071"></a>00071 <span class="keywordflow">if</span> (sample)
<a name="l00072"></a>00072 t0 += sample-><a class="code" href="structSample.html#4a1ae5fbae61678e57efaf185a319ceb">oneD</a>[<a class="code" href="classSingleScattering.html#c6efdeb8681eeb9533d9276b1b7bc1c9">scatterSampleOffset</a>][0] * step;
<a name="l00073"></a>00073 <span class="keywordflow">else</span>
<a name="l00074"></a>00074 t0 += <a class="code" href="pbrt_8h.html#4f11994534b888fcf650c04b5d61d9d4">RandomFloat</a>() * step;
<a name="l00075"></a>00075 <span class="comment">// Compute sample patterns for single scattering samples</span>
<a name="l00076"></a>00076 <span class="keywordtype">float</span> *samp = (<span class="keywordtype">float</span> *)alloca(3 * N * <span class="keyword">sizeof</span>(<span class="keywordtype">float</span>));
<a name="l00077"></a>00077 <a class="code" href="sampling_8cpp.html#63ab80f9467a105c11415509b6a3f45a">LatinHypercube</a>(samp, N, 3);
<a name="l00078"></a>00078 <span class="keywordtype">int</span> sampOffset = 0;
<a name="l00079"></a>00079 <span class="keywordflow">for</span> (<span class="keywordtype">int</span> i = 0; i < N; ++i, t0 += step) {
<a name="l00080"></a>00080 <span class="comment">// Advance to sample at _t0_ and update _T_</span>
<a name="l00081"></a>00081 pPrev = p;
<a name="l00082"></a>00082 p = ray(t0);
<a name="l00083"></a>00083 <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="l00084"></a>00084 .5f * <a class="code" href="classSingleScattering.html#438fa6a0b44fab5f1da7df70a78430cd">stepSize</a>, <a class="code" href="pbrt_8h.html#4f11994534b888fcf650c04b5d61d9d4">RandomFloat</a>());
<a name="l00085"></a>00085 Tr *= Exp(-stepTau);
<a name="l00086"></a>00086 <span class="comment">// Possibly terminate raymarching if transmittance is small</span>
<a name="l00087"></a>00087 <span class="keywordflow">if</span> (Tr.<a class="code" href="classSpectrum.html#25d4cb8d137b7bb0f85e636ea41461a8">y</a>() < 1e-3) {
<a name="l00088"></a>00088 <span class="keyword">const</span> <span class="keywordtype">float</span> continueProb = .5f;
<a name="l00089"></a>00089 <span class="keywordflow">if</span> (<a class="code" href="pbrt_8h.html#4f11994534b888fcf650c04b5d61d9d4">RandomFloat</a>() > continueProb) <span class="keywordflow">break</span>;
<a name="l00090"></a>00090 Tr /= continueProb;
<a name="l00091"></a>00091 }
<a name="l00092"></a>00092 <span class="comment">// Compute single-scattering source term at _p_</span>
<a name="l00093"></a>00093 Lv += Tr * vr-><a class="code" href="classVolumeRegion.html#204a4159db9cf97002a98ff65725d557">Lve</a>(p, w);
<a name="l00094"></a>00094 <a class="code" href="classSpectrum.html">Spectrum</a> ss = vr-><a class="code" href="classVolumeRegion.html#7b8fc74ae58026a7dbf9b29b4d125998">sigma_s</a>(p, w);
<a name="l00095"></a>00095 <span class="keywordflow">if</span> (!ss.<a class="code" href="classSpectrum.html#a05b9a07476998192a83fcd015b7619f">Black</a>() && scene-><a class="code" href="classScene.html#546553c8f864fd2aa709ad95a1d5ecc9">lights</a>.size() > 0) {
<a name="l00096"></a>00096 <span class="keywordtype">int</span> nLights = scene-><a class="code" href="classScene.html#546553c8f864fd2aa709ad95a1d5ecc9">lights</a>.size();
<a name="l00097"></a>00097 <span class="keywordtype">int</span> lightNum =
<a name="l00098"></a>00098 min(<a class="code" href="pbrt_8h.html#02648670ea7bf29f5782902cd9aa87c1">Floor2Int</a>(samp[sampOffset] * nLights),
<a name="l00099"></a>00099 nLights-1);
<a name="l00100"></a>00100 <a class="code" href="classLight.html">Light</a> *light = scene-><a class="code" href="classScene.html#546553c8f864fd2aa709ad95a1d5ecc9">lights</a>[lightNum];
<a name="l00101"></a>00101 <span class="comment">// Add contribution of _light_ due to scattering at _p_</span>
<a name="l00102"></a>00102 <span class="keywordtype">float</span> pdf;
<a name="l00103"></a>00103 <a class="code" href="structVisibilityTester.html">VisibilityTester</a> vis;
<a name="l00104"></a>00104 <a class="code" href="classVector.html">Vector</a> wo;
<a name="l00105"></a>00105 <span class="keywordtype">float</span> u1 = samp[sampOffset+1], u2 = samp[sampOffset+2];
<a name="l00106"></a>00106 <a class="code" href="classSpectrum.html">Spectrum</a> L = light-><a class="code" href="classLight.html#cc1f14dae6074cc9c16b7387020e814c">Sample_L</a>(p, u1, u2, &wo, &pdf, &vis);
<a name="l00107"></a>00107 <span class="keywordflow">if</span> (!L.<a class="code" href="classSpectrum.html#a05b9a07476998192a83fcd015b7619f">Black</a>() && pdf > 0.f && vis.<a class="code" href="structVisibilityTester.html#07e2c29afee9b3d6df35fd367861a19d">Unoccluded</a>(scene)) {
<a name="l00108"></a>00108 <a class="code" href="classSpectrum.html">Spectrum</a> Ld = L * vis.<a class="code" href="structVisibilityTester.html#21b6d9b0540abf25e1c593bc2a6b2f79">Transmittance</a>(scene);
<a name="l00109"></a>00109 Lv += Tr * ss * vr-><a class="code" href="classVolumeRegion.html#53101ab357b591db384fbae6036df9cd">p</a>(p, w, -wo) *
<a name="l00110"></a>00110 Ld * float(nLights) / pdf;
<a name="l00111"></a>00111 }
<a name="l00112"></a>00112 }
<a name="l00113"></a>00113 sampOffset += 3;
<a name="l00114"></a>00114 }
<a name="l00115"></a>00115 <span class="keywordflow">return</span> Lv * step;
<a name="l00116"></a>00116 }
<a name="l00117"></a><a class="code" href="single_8cpp.html#53ba186b32690142f1807bb0f1a16342">00117</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="l00118"></a>00118 <span class="keywordtype">float</span> <a class="code" href="classSingleScattering.html#438fa6a0b44fab5f1da7df70a78430cd">stepSize</a> = params.<a class="code" href="classParamSet.html#87143fd8e73a75082179a110d42531a4">FindOneFloat</a>(<span class="stringliteral">"stepsize"</span>, 1.f);
<a name="l00119"></a>00119 <span class="keywordflow">return</span> <span class="keyword">new</span> <a class="code" href="classSingleScattering.html#4f0137f56ab4b93b53c6adaf2813d782">SingleScattering</a>(stepSize);
<a name="l00120"></a>00120 }
</pre></div></div>
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