SampledSpectrum PathTracingRenderer::Job::contribution(const Scene &scene, const WavelengthSamples &initWLs, const Ray &initRay, IndependentLightPathSampler &pathSampler, ArenaAllocator &mem) const {
WavelengthSamples wls = initWLs;
Ray ray = initRay;
SurfacePoint surfPt;
SampledSpectrum alpha = SampledSpectrum::One;
float initY = alpha.importance(wls.selectedLambda);
SampledSpectrumSum sp(SampledSpectrum::Zero);
uint32_t pathLength = 0;
Intersection isect;
if (!scene.intersect(ray, &isect))
return SampledSpectrum::Zero;
isect.getSurfacePoint(&surfPt);
Vector3D dirOut_sn = surfPt.shadingFrame.toLocal(-ray.dir);
if (surfPt.isEmitting()) {
EDF* edf = surfPt.createEDF(wls, mem);
SampledSpectrum Le = surfPt.emittance(wls) * edf->evaluate(EDFQuery(), dirOut_sn);
sp += alpha * Le;
}
if (surfPt.atInfinity)
return sp;
while (true) {
++pathLength;
if (pathLength >= 100)
break;
Normal3D gNorm_sn = surfPt.shadingFrame.toLocal(surfPt.gNormal);
BSDF* bsdf = surfPt.createBSDF(wls, mem);
BSDFQuery fsQuery(dirOut_sn, gNorm_sn, wls.selectedLambda);
// Next Event Estimation (explicit light sampling)
if (bsdf->hasNonDelta()) {
float lightProb;
Light light;
scene.selectLight(pathSampler.getLightSelectionSample(), &light, &lightProb);
SLRAssert(!std::isnan(lightProb) && !std::isinf(lightProb), "lightProb: unexpected value detected: %f", lightProb);
LightPosQuery lpQuery(ray.time, wls);
LightPosQueryResult lpResult;
SampledSpectrum M = light.sample(lpQuery, pathSampler.getLightPosSample(), &lpResult);
SLRAssert(!std::isnan(lpResult.areaPDF)/* && !std::isinf(xpResult.areaPDF)*/, "areaPDF: unexpected value detected: %f", lpResult.areaPDF);
if (scene.testVisibility(surfPt, lpResult.surfPt, ray.time)) {
float dist2;
Vector3D shadowDir = lpResult.surfPt.getDirectionFrom(surfPt.p, &dist2);
Vector3D shadowDir_l = lpResult.surfPt.shadingFrame.toLocal(-shadowDir);
Vector3D shadowDir_sn = surfPt.shadingFrame.toLocal(shadowDir);
EDF* edf = lpResult.surfPt.createEDF(wls, mem);
SampledSpectrum Le = M * edf->evaluate(EDFQuery(), shadowDir_l);
float lightPDF = lightProb * lpResult.areaPDF;
SLRAssert(!Le.hasNaN() && !Le.hasInf(), "Le: unexpected value detected: %s", Le.toString().c_str());
SampledSpectrum fs = bsdf->evaluate(fsQuery, shadowDir_sn);
float cosLight = absDot(-shadowDir, lpResult.surfPt.gNormal);
float bsdfPDF = bsdf->evaluatePDF(fsQuery, shadowDir_sn) * cosLight / dist2;
float MISWeight = 1.0f;
if (!lpResult.posType.isDelta() && !std::isinf(lpResult.areaPDF))
MISWeight = (lightPDF * lightPDF) / (lightPDF * lightPDF + bsdfPDF * bsdfPDF);
SLRAssert(MISWeight <= 1.0f, "Invalid MIS weight: %g", MISWeight);
float G = absDot(shadowDir_sn, gNorm_sn) * cosLight / dist2;
sp += alpha * Le * fs * (G * MISWeight / lightPDF);
SLRAssert(!std::isnan(G) && !std::isinf(G), "G: unexpected value detected: %f", G);
}
}
// get a next direction by sampling BSDF.
BSDFQueryResult fsResult;
SampledSpectrum fs = bsdf->sample(fsQuery, pathSampler.getBSDFSample(), &fsResult);
if (fs == SampledSpectrum::Zero || fsResult.dirPDF == 0.0f)
break;
if (fsResult.dirType.isDispersive()) {
fsResult.dirPDF /= WavelengthSamples::NumComponents;
wls.flags |= WavelengthSamples::LambdaIsSelected;
}
alpha *= fs * absDot(fsResult.dir_sn, gNorm_sn) / fsResult.dirPDF;
SLRAssert(!alpha.hasInf() && !alpha.hasNaN(),
"alpha: %s\nlength: %u, cos: %g, dirPDF: %g",
alpha.toString().c_str(), pathLength, absDot(fsResult.dir_sn, gNorm_sn), fsResult.dirPDF);
Vector3D dirIn = surfPt.shadingFrame.fromLocal(fsResult.dir_sn);
ray = Ray(surfPt.p, dirIn, ray.time, Ray::Epsilon);
// find a next intersection point.
isect = Intersection();
if (!scene.intersect(ray, &isect))
break;
isect.getSurfacePoint(&surfPt);
dirOut_sn = surfPt.shadingFrame.toLocal(-ray.dir);
// implicit light sampling
if (surfPt.isEmitting()) {
float bsdfPDF = fsResult.dirPDF;
EDF* edf = surfPt.createEDF(wls, mem);
SampledSpectrum Le = surfPt.emittance(wls) * edf->evaluate(EDFQuery(), dirOut_sn);
float lightProb = scene.evaluateProb(Light(isect.obj));
float dist2 = surfPt.getSquaredDistance(ray.org);
float lightPDF = lightProb * surfPt.evaluateAreaPDF() * dist2 / absDot(ray.dir, surfPt.gNormal);
SLRAssert(!Le.hasNaN() && !Le.hasInf(), "Le: unexpected value detected: %s", Le.toString().c_str());
SLRAssert(!std::isnan(lightPDF)/* && !std::isinf(lightPDF)*/, "lightPDF: unexpected value detected: %f", lightPDF);
float MISWeight = 1.0f;
if (!fsResult.dirType.isDelta())
MISWeight = (bsdfPDF * bsdfPDF) / (lightPDF * lightPDF + bsdfPDF * bsdfPDF);
SLRAssert(MISWeight <= 1.0f, "Invalid MIS weight: %g", MISWeight);
sp += alpha * Le * MISWeight;
}
if (surfPt.atInfinity)
break;
// Russian roulette
float continueProb = std::min(alpha.importance(wls.selectedLambda) / initY, 1.0f);
if (pathSampler.getPathTerminationSample() < continueProb)
alpha /= continueProb;
else
break;
}
return sp;
}
