void VolumePatIntegrator::EyeRandomWalk(const Scene *scene, const Ray &eyeRay,
VolumeVertexList& vertexList, RNG &rng) const {
// Do a random walk for the eye ray in the volume
Spectrum cummulative(1.f);
// Find the intersection between the eye ray and the volume
VolumeRegion *vr = scene->volumeRegion;
float t0, t1;
if (!vr || !vr->IntersectP(eyeRay, &t0, &t1) || (t1-t0) == 0.f || t0 < 0.f) {
return;
}
// Find the intersection point between the sampled light ray and the volume
RayDifferential ray(eyeRay);
Point p = ray(t0), pPrev;
uint64_t bounces = 0;
while(vr->WorldBound().Inside(p)) {
Vector wi = -ray.d;
const Spectrum sigma_a = vr->Sigma_a(p, wi, eyeRay.time);
const Spectrum sigma_s = vr->Sigma_s(p, wi, eyeRay.time);
const Spectrum STER = vr->STER(p, wi, eyeRay.time);
// Construct and add the _eyeVertex_ to the _vertexList_
VolumeVertex eyeVertex(p, wi, sigma_a, sigma_s, cummulative, 1.0);
vertexList.push_back(eyeVertex);
// Sample the direction of the next event
float directionPdf = 1.f;
Vector wo;
if(STER.y() > rng.RandomFloat()) {
// Change the ray direction due to a scattering event at _p_
if(!vr->SampleDirection(p, wi, wo, &directionPdf, rng)) {
break; // Direction error
}
// Account for the losses due to the scattering event at _p_
cummulative *= sigma_s * vr->p(p, wi, wo, ray.time);
} else {
// Account only for the trnsmittance between the previous and the
// next events becuse there is no direction change.
wo = ray.d;
}
// Sample the distance of the next event
ray = RayDifferential(p, wo, 0, INFINITY);
float tDist;
float distancePdf = 1.f;
Point Psample;
if(!vr->SampleDistance(ray, &tDist, Psample, &distancePdf, rng)) {
break; // The sampled point is outside the volume
}
// Account for the sampling Pdfs from sampling a direction and/or distance
const float pdf = distancePdf * directionPdf;
cummulative *= 1 / pdf;
// Update the events and account for the transmittance between the events
pPrev = p;
p = Psample;
const Ray tauRay(pPrev, p - pPrev, 0.f, 1.f, ray.time, ray.depth);
const Spectrum stepTau = vr->tau(tauRay, .5f * stepSize, rng.RandomFloat());
const Spectrum TrPP = Exp(-stepTau);
cummulative *= TrPP;
// Possibly terminate ray marching if _cummulative_ is small
if (cummulative.y() < 1e-3) {
const float continueProb = .5f;
if (rng.RandomFloat() > continueProb) {
cummulative = 0.f;
break;
}
cummulative /= continueProb;
}
// Terminate if bounces are more than requested
bounces++;
if (bounces > maxDepth) {
break;
}
}
}
void UniformResamplingRecursiveMISBPTRenderer::processSample(uint32_t threadID, uint32_t tileID, uint32_t pixelID, uint32_t sampleID,
uint32_t x, uint32_t y) const {
auto mis = [&](float v) {
return Mis(v);
};
ThreadRNG rng(*this, threadID);
PixelSensor pixelSensor(getSensor(), Vec2u(x, y), getFramebufferSize());
auto pixelSample = getPixelSample(threadID, sampleID);
auto sensorSample = getFloat2(threadID);
auto fImportanceScale = 1.f / getSppCount();
BDPTPathVertex eyeVertex(getScene(), pixelSensor, sensorSample, pixelSample, m_nLightPathCount, mis);
if(eyeVertex.m_Power == zero<Vec3f>() || !eyeVertex.m_fPathPdf) {
return;
}
// Sample the light path to connect with the eye path
auto lightPathIdx = clamp(std::size_t(getFloat(threadID) * m_nLightPathCount),
std::size_t(0),
m_nLightPathCount - 1);
auto pLightPath = m_LightPathBuffer.getSlicePtr(lightPathIdx);
auto maxEyePathDepth = getMaxEyePathDepth();
auto maxLightPathDepth = getMaxLightPathDepth();
auto extendEyePath = [&]() -> bool {
return eyeVertex.m_nDepth < maxEyePathDepth &&
eyeVertex.extend(eyeVertex, getScene(), getSppCount(), false, rng, mis);
};
// Iterate over an eye path
do {
// Intersection with light source
auto totalLength = eyeVertex.m_nDepth;
if(acceptPathDepth(totalLength) && totalLength <= m_nMaxDepth) {
auto contrib = fImportanceScale * computeEmittedRadiance(eyeVertex, getScene(), m_LightSampler, getSppCount(), mis);
if(isInvalidMeasurementEstimate(contrib)) {
reportInvalidContrib(threadID, tileID, pixelID, [&]() {
debugLog() << "s = " << 0 << ", t = " << (eyeVertex.m_nDepth + 1) << std::endl;
});
}
accumulate(FINAL_RENDER, pixelID, Vec4f(contrib, 0));
accumulate(FINAL_RENDER_DEPTH1 + totalLength - 1u, pixelID, Vec4f(contrib, 0));
auto strategyOffset = computeBPTStrategyOffset(totalLength + 1, 0u);
accumulate(BPT_STRATEGY_s0_t2 + strategyOffset, pixelID, Vec4f(contrib, 0));
}
// Connections
if(eyeVertex.m_Intersection) {
// Direct illumination
auto totalLength = eyeVertex.m_nDepth + 1;
if(acceptPathDepth(totalLength) && totalLength <= m_nMaxDepth) {
float lightPdf;
auto pLight = m_LightSampler.sample(getScene(), getFloat(threadID), lightPdf);
auto s2D = getFloat2(threadID);
auto contrib = fImportanceScale * connectVertices(eyeVertex, EmissionVertex(pLight, lightPdf, s2D), getScene(), getSppCount(), mis);
if(isInvalidMeasurementEstimate(contrib)) {
reportInvalidContrib(threadID, tileID, pixelID, [&]() {
debugLog() << "s = " << 1 << ", t = " << (eyeVertex.m_nDepth + 1) << std::endl;
});
}
accumulate(FINAL_RENDER, pixelID, Vec4f(contrib, 0));
accumulate(FINAL_RENDER_DEPTH1 + totalLength - 1u, pixelID, Vec4f(contrib, 0));
auto strategyOffset = computeBPTStrategyOffset(totalLength + 1, 1);
accumulate(BPT_STRATEGY_s0_t2 + strategyOffset, pixelID, Vec4f(contrib, 0));
}
// Connection with each light vertex
for(auto j = 0u; j < maxLightPathDepth; ++j) {
auto pLightVertex = pLightPath + j;
auto totalLength = eyeVertex.m_nDepth + pLightVertex->m_nDepth + 1;
if(pLightVertex->m_fPathPdf > 0.f && acceptPathDepth(totalLength) && totalLength <= m_nMaxDepth) {
auto contrib = fImportanceScale * connectVertices(eyeVertex, *pLightVertex, getScene(), getSppCount(), mis);
if(isInvalidMeasurementEstimate(contrib)) {
reportInvalidContrib(threadID, tileID, pixelID, [&]() {
debugLog() << "s = " << (pLightVertex->m_nDepth + 1) << ", t = " << (eyeVertex.m_nDepth + 1) << std::endl;
});
}
accumulate(FINAL_RENDER, pixelID, Vec4f(contrib, 0));
accumulate(FINAL_RENDER_DEPTH1 + totalLength - 1u, pixelID, Vec4f(contrib, 0));
auto strategyOffset = computeBPTStrategyOffset(totalLength + 1, pLightVertex->m_nDepth + 1);
accumulate(BPT_STRATEGY_s0_t2 + strategyOffset, pixelID, Vec4f(contrib, 0));
}
}
}
} while(extendEyePath());
}