static Spectrum L(const Scene *scene, const Renderer *renderer,
const Camera *camera, MemoryArena &arena, RNG &rng, int maxDepth,
bool ignoreDirect, const MLTSample &sample) {
// Generate camera ray from Metropolis sample
RayDifferential ray;
float cameraWeight = camera->GenerateRayDifferential(sample.cameraSample,
&ray);
Spectrum pathThroughput = cameraWeight, L = 0.;
bool specularBounce = false, allSpecular = true;
for (int pathLength = 0; pathLength < maxDepth; ++pathLength) {
// Find next intersection in Metropolis light path
Intersection isect;
if (!scene->Intersect(ray, &isect)) {
bool includeLe = ignoreDirect ? (specularBounce && !allSpecular) :
(pathLength == 0 || specularBounce);
if (includeLe)
for (uint32_t i = 0; i < scene->lights.size(); ++i)
L += pathThroughput * scene->lights[i]->Le(ray);
break;
}
if (ignoreDirect ? (specularBounce && !allSpecular) :
(specularBounce || pathLength == 0))
L += pathThroughput * isect.Le(-ray.d);
BSDF *bsdf = isect.GetBSDF(ray, arena);
const Point &p = bsdf->dgShading.p;
const Normal &n = bsdf->dgShading.nn;
Vector wo = -ray.d;
const PathSample &ps = sample.pathSamples[pathLength];
// Sample direct illumination for Metropolis path vertex
if (!ignoreDirect || pathLength > 0) {
LightSample lightSample(ps.lightDir0, ps.lightDir1, ps.lightNum0);
BSDFSample bsdfSample(ps.bsdfLightDir0, ps.bsdfLightDir1,
ps.bsdfLightComponent);
uint32_t lightNum = Floor2Int(ps.lightNum1 * scene->lights.size());
lightNum = min(lightNum, (uint32_t)(scene->lights.size()-1));
const Light *light = scene->lights[lightNum];
L += pathThroughput *
EstimateDirect(scene, renderer, arena, light, p, n, wo,
isect.rayEpsilon, sample.cameraSample.time, bsdf, rng,
lightSample, bsdfSample);
}
// Sample direction for outgoing Metropolis path direction
BSDFSample outgoingBSDFSample(ps.bsdfDir0, ps.bsdfDir1,
ps.bsdfComponent);
Vector wi;
float pdf;
BxDFType flags;
Spectrum f = bsdf->Sample_f(wo, &wi, outgoingBSDFSample,
&pdf, BSDF_ALL, &flags);
if (f.IsBlack() || pdf == 0.)
break;
specularBounce = (flags & BSDF_SPECULAR) != 0;
allSpecular &= specularBounce;
pathThroughput *= f * AbsDot(wi, n) / pdf;
ray = RayDifferential(p, wi, ray, isect.rayEpsilon);
//pathThroughput *= renderer->Transmittance(scene, ray, NULL, rng, arena);
}
return L;
}
Vec3f TraceBase::sampleDirect(const Primitive &light,
SurfaceScatterEvent &event,
const Medium *medium,
int bounce,
const Ray &parentRay,
Vec3f *transmittance)
{
Vec3f result(0.0f);
if (event.info->bsdf->lobes().isPureSpecular() || event.info->bsdf->lobes().isForward())
return Vec3f(0.0f);
result += lightSample(light, event, medium, bounce, parentRay, transmittance);
if (!light.isDirac())
result += bsdfSample(light, event, medium, bounce, parentRay);
return result;
}
void IGIIntegrator::Preprocess(const Scene *scene, const Camera *camera,
const Renderer *renderer) {
if (scene->lights.size() == 0) return;
MemoryArena arena;
RNG rng;
// Compute samples for emitted rays from lights
vector<float> lightNum(nLightPaths * nLightSets);
vector<float> lightSampPos(2 * nLightPaths * nLightSets, 0.f);
vector<float> lightSampComp(nLightPaths * nLightSets, 0.f);
vector<float> lightSampDir(2 * nLightPaths * nLightSets, 0.f);
LDShuffleScrambled1D(nLightPaths, nLightSets, &lightNum[0], rng);
LDShuffleScrambled2D(nLightPaths, nLightSets, &lightSampPos[0], rng);
LDShuffleScrambled1D(nLightPaths, nLightSets, &lightSampComp[0], rng);
LDShuffleScrambled2D(nLightPaths, nLightSets, &lightSampDir[0], rng);
// Precompute information for light sampling densities
Distribution1D *lightDistribution = ComputeLightSamplingCDF(scene);
for (uint32_t s = 0; s < nLightSets; ++s) {
for (uint32_t i = 0; i < nLightPaths; ++i) {
// Follow path _i_ from light to create virtual lights
int sampOffset = s*nLightPaths + i;
// Choose light source to trace virtual light path from
float lightPdf;
int ln = lightDistribution->SampleDiscrete(lightNum[sampOffset],
&lightPdf);
Light *light = scene->lights[ln];
// Sample ray leaving light source for virtual light path
RayDifferential ray;
float pdf;
LightSample ls(lightSampPos[2*sampOffset], lightSampPos[2*sampOffset+1],
lightSampComp[sampOffset]);
Normal Nl;
Spectrum alpha = light->Sample_L(scene, ls, lightSampDir[2*sampOffset],
lightSampDir[2*sampOffset+1],
camera->shutterOpen, &ray, &Nl, &pdf);
if (pdf == 0.f || alpha.IsBlack()) continue;
alpha /= pdf * lightPdf;
Intersection isect;
while (scene->Intersect(ray, &isect) && !alpha.IsBlack()) {
// Create virtual light and sample new ray for path
alpha *= renderer->Transmittance(scene, RayDifferential(ray), NULL,
rng, arena);
Vector wo = -ray.d;
BSDF *bsdf = isect.GetBSDF(ray, arena);
// Create virtual light at ray intersection point
Spectrum contrib = alpha * bsdf->rho(wo, rng) / M_PI;
virtualLights[s].push_back(VirtualLight(isect.dg.p, isect.dg.nn, contrib,
isect.rayEpsilon));
// Sample new ray direction and update weight for virtual light path
Vector wi;
float pdf;
BSDFSample bsdfSample(rng);
Spectrum fr = bsdf->Sample_f(wo, &wi, bsdfSample, &pdf);
if (fr.IsBlack() || pdf == 0.f)
break;
Spectrum contribScale = fr * AbsDot(wi, bsdf->dgShading.nn) / pdf;
// Possibly terminate virtual light path with Russian roulette
float rrProb = min(1.f, contribScale.y());
if (rng.RandomFloat() > rrProb)
break;
alpha *= contribScale / rrProb;
ray = RayDifferential(isect.dg.p, wi, ray, isect.rayEpsilon);
}
arena.FreeAll();
}
}
delete lightDistribution;
}
Spectrum PhotonIntegrator::Li(const Scene *scene, const Renderer *renderer,
const RayDifferential &ray, const Intersection &isect,
const Sample *sample, RNG &rng, MemoryArena &arena) const {
Spectrum L(0.);
Vector wo = -ray.d;
// Compute emitted light if ray hit an area light source
L += isect.Le(wo);
// Evaluate BSDF at hit pbrt::Point
BSDF *bsdf = isect.GetBSDF(ray, arena);
const pbrt::Point &p = bsdf->dgShading.p;
const Normal &n = bsdf->dgShading.nn;
L += UniformSampleAllLights(scene, renderer, arena, p, n,
wo, isect.rayEpsilon, ray.time, bsdf, sample, rng,
lightSampleOffsets, bsdfSampleOffsets);
// Compute caustic lighting for photon map integrator
ClosePhoton *lookupBuf = arena.Alloc<ClosePhoton>(nLookup);
L += LPhoton(causticMap, nCausticPaths, nLookup, lookupBuf, bsdf,
rng, isect, wo, maxDistSquared);
// Compute indirect lighting for photon map integrator
if (finalGather && indirectMap != NULL) {
#if 1
// Do one-bounce final gather for photon map
BxDFType nonSpecular = BxDFType(BSDF_REFLECTION |
BSDF_TRANSMISSION | BSDF_DIFFUSE | BSDF_GLOSSY);
if (bsdf->NumComponents(nonSpecular) > 0) {
// Find indirect photons around point for importance sampling
const uint32_t nIndirSamplePhotons = 50;
PhotonProcess proc(nIndirSamplePhotons,
arena.Alloc<ClosePhoton>(nIndirSamplePhotons));
float searchDist2 = maxDistSquared;
while (proc.nFound < nIndirSamplePhotons) {
float md2 = searchDist2;
proc.nFound = 0;
indirectMap->Lookup(p, proc, md2);
searchDist2 *= 2.f;
}
// Copy photon directions to local array
Vector *photonDirs = arena.Alloc<Vector>(nIndirSamplePhotons);
for (uint32_t i = 0; i < nIndirSamplePhotons; ++i)
photonDirs[i] = proc.photons[i].photon->wi;
// Use BSDF to do final gathering
Spectrum Li = 0.;
for (int i = 0; i < gatherSamples; ++i) {
// Sample random direction from BSDF for final gather ray
Vector wi;
float pdf;
BSDFSample bsdfSample(sample, bsdfGatherSampleOffsets, i);
Spectrum fr = bsdf->Sample_f(wo, &wi, bsdfSample,
&pdf, BxDFType(BSDF_ALL & ~BSDF_SPECULAR));
if (fr.IsBlack() || pdf == 0.f) continue;
Assert(pdf >= 0.f);
// Trace BSDF final gather ray and accumulate radiance
RayDifferential bounceRay(p, wi, ray, isect.rayEpsilon);
Intersection gatherIsect;
if (scene->Intersect(bounceRay, &gatherIsect)) {
// Compute exitant radiance _Lindir_ using radiance photons
Spectrum Lindir = 0.f;
Normal nGather = gatherIsect.dg.nn;
nGather = Faceforward(nGather, -bounceRay.d);
RadiancePhotonProcess proc(nGather);
float md2 = INFINITY;
radianceMap->Lookup(gatherIsect.dg.p, proc, md2);
if (proc.photon != NULL)
Lindir = proc.photon->Lo;
Lindir *= renderer->Transmittance(scene, bounceRay, NULL, rng, arena);
// Compute MIS weight for BSDF-sampled gather ray
// Compute PDF for photon-sampling of direction _wi_
float photonPdf = 0.f;
float conePdf = UniformConePdf(cosGatherAngle);
for (uint32_t j = 0; j < nIndirSamplePhotons; ++j)
if (Dot(photonDirs[j], wi) > .999f * cosGatherAngle)
photonPdf += conePdf;
photonPdf /= nIndirSamplePhotons;
float wt = PowerHeuristic(gatherSamples, pdf, gatherSamples, photonPdf);
Li += fr * Lindir * (AbsDot(wi, n) * wt / pdf);
}
}
L += Li / gatherSamples;
// Use nearby photons to do final gathering
Li = 0.;
for (int i = 0; i < gatherSamples; ++i) {
// Sample random direction using photons for final gather ray
BSDFSample gatherSample(sample, indirGatherSampleOffsets, i);
int photonNum = min((int)nIndirSamplePhotons - 1,
Floor2Int(gatherSample.uComponent * nIndirSamplePhotons));
// Sample gather ray direction from _photonNum_
Vector vx, vy;
CoordinateSystem(photonDirs[photonNum], &vx, &vy);
Vector wi = UniformSampleCone(gatherSample.uDir[0], gatherSample.uDir[1],
cosGatherAngle, vx, vy, photonDirs[photonNum]);
// Trace photon-sampled final gather ray and accumulate radiance
Spectrum fr = bsdf->f(wo, wi);
if (fr.IsBlack()) continue;
RayDifferential bounceRay(p, wi, ray, isect.rayEpsilon);
Intersection gatherIsect;
PBRT_PHOTON_MAP_STARTED_GATHER_RAY(&bounceRay);
if (scene->Intersect(bounceRay, &gatherIsect)) {
// Compute exitant radiance _Lindir_ using radiance photons
Spectrum Lindir = 0.f;
Normal nGather = gatherIsect.dg.nn;
nGather = Faceforward(nGather, -bounceRay.d);
RadiancePhotonProcess proc(nGather);
float md2 = INFINITY;
radianceMap->Lookup(gatherIsect.dg.p, proc, md2);
if (proc.photon != NULL)
Lindir = proc.photon->Lo;
Lindir *= renderer->Transmittance(scene, bounceRay, NULL, rng, arena);
// Compute PDF for photon-sampling of direction _wi_
float photonPdf = 0.f;
float conePdf = UniformConePdf(cosGatherAngle);
for (uint32_t j = 0; j < nIndirSamplePhotons; ++j)
if (Dot(photonDirs[j], wi) > .999f * cosGatherAngle)
photonPdf += conePdf;
photonPdf /= nIndirSamplePhotons;
// Compute MIS weight for photon-sampled gather ray
float bsdfPdf = bsdf->Pdf(wo, wi);
float wt = PowerHeuristic(gatherSamples, photonPdf, gatherSamples, bsdfPdf);
Li += fr * Lindir * AbsDot(wi, n) * wt / photonPdf;
}
PBRT_PHOTON_MAP_FINISHED_GATHER_RAY(&bounceRay);
}
L += Li / gatherSamples;
}
#else
// for debugging / examples: use the photon map directly
Normal nn = Faceforward(n, -ray.d);
RadiancePhotonProcess proc(nn);
float md2 = INFINITY;
radianceMap->Lookup(p, proc, md2);
if (proc.photon)
L += proc.photon->Lo;
#endif
}
else
L += LPhoton(indirectMap, nIndirectPaths, nLookup, lookupBuf,
bsdf, rng, isect, wo, maxDistSquared);
if (ray.depth+1 < maxSpecularDepth) {
Vector wi;
// Trace rays for specular reflection and refraction
L += SpecularReflect(ray, bsdf, rng, isect, renderer, scene, sample,
arena);
L += SpecularTransmit(ray, bsdf, rng, isect, renderer, scene, sample,
arena);
}
return L;
}
Spectrum MisPathTracer::Li(const Scene* scene, Sampler& sampler, Ray3f& ray) const
{
Spectrum L(0.f);
Intersection its;
Spectrum throughput(1.f);
bool isSpecular = true;
while (true)
{
if (!scene->rayIntersect(ray, its))
break;
if (isSpecular && its.shape->getEmitter())
{
EmitterSample emittanceSample(ray.o, its.p, its.shFrame.n);
L += throughput * its.shape->getEmitter()->eval(emittanceSample);
}
if (its.shape->getBSDF()->getType() != BSDFType::Delta)
{
EmitterSample emSam(its.p);
auto lightSpec = scene->sampleEmitter(its, sampler, emSam);
float cosFactor = its.shFrame.n.dot(emSam.wi);
if (!(cosFactor <= 0.f || lightSpec.isZero() || scene->rayIntersect(emSam.shadowRay)))
{
BSDFSample bsdfSam(its.p, its.toLocal(-ray.d), its.toLocal(emSam.wi));
bsdfSam.measure = Measure::SolidAngle;
auto bsdfSpec = its.shape->getBSDF()->eval(bsdfSam);
float pdfEm = emSam.pdf;
float pdfBsdf = its.shape->getBSDF()->pdf(bsdfSam);
L += throughput * bsdfSpec * lightSpec * cosFactor * miWeight(pdfEm, pdfBsdf);
}
}
BSDFSample bsdfSample(its.p, its.toLocal(-ray.d));
auto bsdf = its.shape->getBSDF()->sample(bsdfSample, sampler);
Intersection bsdfIts;
Ray3f bsdfRay(its.p, its.toWorld(bsdfSample.wo));
if (scene->rayIntersect(bsdfRay, bsdfIts) && bsdfIts.shape->getEmitter())
{
const auto* em = bsdfIts.shape->getEmitter();
EmitterSample emSam(its.p, bsdfIts.p, bsdfIts.shFrame.n);
emSam.wi = bsdfRay.d;
auto lightSpec = em->eval(emSam);
float pdfBsdf = its.shape->getBSDF()->pdf(bsdfSample);
float pdfEm = em->pdf(emSam) * scene->getEmitterPdf();
if (pdfBsdf + pdfEm > 0.f)
L += throughput * bsdf * lightSpec * miWeight(pdfBsdf, pdfEm);
}
isSpecular = its.shape->getBSDF()->getType() == BSDFType::Delta;
throughput *= bsdf;
ray = bsdfRay;
float q = 1.f - std::min(throughput.maxCoeff(), 0.99f);
if (sampler.next1D() > q)
throughput /= (1.f - q);
else
break;
}
return L;
}
