Spectrum DirectLightingIntegrator::Li(const RayDifferential &ray,
const Scene &scene, Sampler &sampler,
MemoryArena &arena, int depth) const {
ProfilePhase p(Prof::SamplerIntegratorLi);
Spectrum L(0.f);
// Find closest ray intersection or return background radiance
SurfaceInteraction isect;
if (!scene.Intersect(ray, &isect)) {
for (const auto &light : scene.lights) L += light->Le(ray);
return L;
}
// Compute scattering functions for surface interaction
isect.ComputeScatteringFunctions(ray, arena);
if (!isect.bsdf)
return Li(isect.SpawnRay(ray.d), scene, sampler, arena, depth);
Vector3f wo = isect.wo;
// Compute emitted light if ray hit an area light source
L += isect.Le(wo);
if (scene.lights.size() > 0) {
// Compute direct lighting for _DirectLightingIntegrator_ integrator
if (strategy == LightStrategy::UniformSampleAll)
L += UniformSampleAllLights(isect, scene, arena, sampler,
nLightSamples);
else
L += UniformSampleOneLight(isect, scene, arena, sampler);
}
if (depth + 1 < maxDepth) {
Vector3f wi;
// Trace rays for specular reflection and refraction
L += SpecularReflect(ray, isect, scene, sampler, arena, depth);
L += SpecularTransmit(ray, isect, scene, sampler, arena, depth);
}
return L;
}
COREDLL Spectrum WeightedSampleOneLight(const Scene *scene,
const Point &p, const Normal &n,
const Vector &wo, BSDF *bsdf,
const Sample *sample, int lightSampleOffset,
int lightNumOffset, int bsdfSampleOffset,
int bsdfComponentOffset, float *&avgY,
float *&avgYsample, float *&cdf,
float &overallAvgY) {
int nLights = int(scene->lights.size());
// Initialize _avgY_ array if necessary
if (!avgY) {
avgY = new float[nLights];
avgYsample = new float[nLights];
cdf = new float[nLights+1];
for (int i = 0; i < nLights; ++i)
avgY[i] = avgYsample[i] = 0.;
}
Spectrum L(0.);
if (overallAvgY == 0.) {
// Sample one light uniformly and initialize luminance arrays
L = UniformSampleOneLight(scene, p, n,
wo, bsdf, sample, lightSampleOffset,
lightNumOffset, bsdfSampleOffset,
bsdfComponentOffset);
float luminance = L.y();
overallAvgY = luminance;
for (int i = 0; i < nLights; ++i)
avgY[i] = luminance;
}
else {
// Choose _light_ according to average reflected luminance
float c, lightSampleWeight;
for (int i = 0; i < nLights; ++i)
avgYsample[i] = max(avgY[i], .1f * overallAvgY);
ComputeStep1dCDF(avgYsample, nLights, &c, cdf);
float t = SampleStep1d(avgYsample, cdf, c, nLights,
sample->oneD[lightNumOffset][0], &lightSampleWeight);
int lightNum = min(Float2Int(nLights * t), nLights-1);
Light *light = scene->lights[lightNum];
L = EstimateDirect(scene, light, p, n, wo, bsdf,
sample, lightSampleOffset, bsdfSampleOffset,
bsdfComponentOffset, 0);
// Update _avgY_ array with reflected radiance due to light
float luminance = L.y();
avgY[lightNum] =
ExponentialAverage(avgY[lightNum], luminance, .99f);
overallAvgY =
ExponentialAverage(overallAvgY, luminance, .999f);
L /= lightSampleWeight;
}
return L;
}
Spectrum BidirIntegrator::Li(const Scene *scene,
const RayDifferential &ray,
const Sample *sample, float *alpha) const {
Spectrum L(0.);
// Generate eye and light sub-paths
BidirVertex eyePath[MAX_VERTS], lightPath[MAX_VERTS];
int nEye = generatePath(scene, ray, sample, eyeBSDFOffset,
eyeBSDFCompOffset, eyePath, MAX_VERTS);
if (nEye == 0) {
*alpha = 0.;
return L;
}
*alpha = 1;
// Choose light for bidirectional path
int lightNum = Floor2Int(sample->oneD[lightNumOffset][0] *
scene->lights.size());
lightNum = min(lightNum, (int)scene->lights.size() - 1);
Light *light = scene->lights[lightNum];
float lightWeight = float(scene->lights.size());
// Sample ray from light source to start light path
Ray lightRay;
float lightPdf;
float u[4];
u[0] = sample->twoD[lightPosOffset][0];
u[1] = sample->twoD[lightPosOffset][1];
u[2] = sample->twoD[lightDirOffset][0];
u[3] = sample->twoD[lightDirOffset][1];
Spectrum Le = light->Sample_L(scene, u[0], u[1], u[2], u[3],
&lightRay, &lightPdf);
if (lightPdf == 0.) return 0.f;
Le = lightWeight / lightPdf;
int nLight = generatePath(scene, lightRay, sample, lightBSDFOffset,
lightBSDFCompOffset, lightPath, MAX_VERTS);
// Connect bidirectional path prefixes and evaluate throughput
Spectrum directWt(1.0);
for (int i = 1; i <= nEye; ++i) {
// Handle direct lighting for bidirectional integrator
directWt /= eyePath[i-1].rrWeight;
L += directWt *
UniformSampleOneLight(scene, eyePath[i-1].p, eyePath[i-1].ng, eyePath[i-1].wi,
eyePath[i-1].bsdf, sample, directLightOffset[i-1], directLightNumOffset[i-1],
directBSDFOffset[i-1], directBSDFCompOffset[i-1]) /
weightPath(eyePath, i, lightPath, 0);
directWt *= eyePath[i-1].bsdf->f(eyePath[i-1].wi, eyePath[i-1].wo) *
AbsDot(eyePath[i-1].wo, eyePath[i-1].ng) /
eyePath[i-1].bsdfWeight;
for (int j = 1; j <= nLight; ++j)
L += Le * evalPath(scene, eyePath, i, lightPath, j) /
weightPath(eyePath, i, lightPath, j);
}
return L;
}
Spectrum IrradianceCacheIntegrator::pathL(Ray &r, const Scene *scene,
const Renderer *renderer, const Sample *sample, MemoryArena &arena) const {
Spectrum L(0.f);
Spectrum pathThroughput = 1.;
RayDifferential ray(r);
bool specularBounce = false;
for (int pathLength = 0; ; ++pathLength) {
// Find next vertex of path
Intersection isect;
if (!scene->Intersect(ray, &isect))
break;
if (pathLength == 0)
r.maxt = ray.maxt;
else if (pathLength == 1)
pathThroughput *= renderer->Transmittance(scene, ray, sample, arena, NULL);
else
pathThroughput *= renderer->Transmittance(scene, ray, NULL, arena, sample->rng);
// Possibly add emitted light at path vertex
if (specularBounce)
L += pathThroughput * isect.Le(-ray.d);
// Evaluate BSDF at hit point
BSDF *bsdf = isect.GetBSDF(ray, arena);
// Sample illumination from lights to find path contribution
const Point &p = bsdf->dgShading.p;
const Normal &n = bsdf->dgShading.nn;
Vector wo = -ray.d;
L += pathThroughput *
UniformSampleOneLight(scene, renderer, arena, p, n, wo, isect.rayEpsilon,
bsdf, sample);
if (pathLength+1 == maxIndirectDepth) break;
// Sample BSDF to get new path direction
// Get random numbers for sampling new direction, \mono{bs1}, \mono{bs2}, and \mono{bcs}
Vector wi;
float pdf;
BxDFType flags;
Spectrum f = bsdf->Sample_f(wo, &wi, BSDFSample(*sample->rng),
&pdf, BSDF_ALL, &flags);
if (f.IsBlack() || pdf == 0.)
break;
specularBounce = (flags & BSDF_SPECULAR) != 0;
pathThroughput *= f * AbsDot(wi, n) / pdf;
ray = RayDifferential(p, wi, ray, isect.rayEpsilon);
// Possibly terminate the path
if (pathLength > 2) {
float rrProb = min(1.f, pathThroughput.y());
if (sample->rng->RandomFloat() > rrProb)
break;
pathThroughput /= rrProb;
}
}
return L;
}
Spectrum DirectLightingIntegrator::Li(const Scene *scene,
const Renderer *renderer, const RayDifferential &ray,
const Intersection &isect, const Sample *sample, RNG &rng, MemoryArena &arena) const {
Spectrum L(0.f);
// Evaluate BSDF at hit point
BSDF *bsdf = isect.GetBSDF(ray, arena);
Vector wo = -ray.d;
const Point &p = bsdf->dgShading.p;
const Normal &n = bsdf->dgShading.nn;
// Compute emitted light if ray hit an area light source
L += isect.Le(wo);
// Compute direct lighting for _DirectLightingIntegrator_ integrator
if (scene->lights.size() > 0) {
// Apply direct lighting strategy
switch (strategy) {
case SAMPLE_ALL_UNIFORM:
L += UniformSampleAllLights(scene, renderer, arena, p, n, wo,
isect.rayEpsilon, ray.time, bsdf, sample, rng,
lightSampleOffsets, bsdfSampleOffsets);
break;
case SAMPLE_ONE_UNIFORM:
L += UniformSampleOneLight(scene, renderer, arena, p, n, wo,
isect.rayEpsilon, ray.time, bsdf, sample, rng,
lightNumOffset, lightSampleOffsets, bsdfSampleOffsets);
break;
}
}
if (ray.depth + 1 < maxDepth) {
Vector wi;
// Trace rays for specular reflection and refraction
Spectrum reflection(0.f);
Spectrum refraction(0.f);
reflection = SpecularReflect(ray, bsdf, rng, isect, renderer, scene,
sample,arena);
refraction = SpecularTransmit(ray, bsdf, rng, isect, renderer, scene,
sample, arena);
L += reflection;
L += refraction;
}
//printf("Size %i \n", NaiadFoam::cur->FoamPlane().size());
return L*bsdf->dgShading.mult;
}
// VolPathIntegrator Method Definitions
Spectrum VolPathIntegrator::Li(const RayDifferential &r, const Scene &scene,
Sampler &sampler, MemoryArena &arena,
int depth) const {
ProfilePhase p(Prof::SamplerIntegratorLi);
Spectrum L(0.f), alpha(1.f);
RayDifferential ray(r);
bool specularBounce = false;
for (int bounces = 0;; ++bounces) {
// Store intersection into _isect_
SurfaceInteraction isect;
bool foundIntersection = scene.Intersect(ray, &isect);
// Sample the participating medium, if present
MediumInteraction mi;
if (ray.medium) alpha *= ray.medium->Sample(ray, sampler, arena, &mi);
if (alpha.IsBlack()) break;
// Handle an interaction with a medium or a surface
if (mi.IsValid()) {
// Handle medium scattering case
Vector3f wo = -ray.d, wi;
L += alpha * UniformSampleOneLight(mi, scene, sampler, arena, true);
Point2f phaseSample = sampler.Get2D();
mi.phase->Sample_p(wo, &wi, phaseSample);
ray = mi.SpawnRay(wi);
} else {
// Handle surface scattering case
// Possibly add emitted light and terminate
if (bounces == 0 || specularBounce) {
// Add emitted light at path vertex or from the environment
if (foundIntersection)
L += alpha * isect.Le(-ray.d);
else
for (const auto &light : scene.lights)
L += alpha * light->Le(ray);
}
if (!foundIntersection || bounces >= maxDepth) break;
// Compute scattering functions and skip over medium boundaries
isect.ComputeScatteringFunctions(ray, arena, true);
if (!isect.bsdf) {
ray = isect.SpawnRay(ray.d);
bounces--;
continue;
}
// Sample illumination from lights to find attenuated path
// contribution
L += alpha *
UniformSampleOneLight(isect, scene, sampler, arena, true);
// Sample BSDF to get new path direction
Vector3f wo = -ray.d, wi;
Float pdf;
BxDFType flags;
Spectrum f = isect.bsdf->Sample_f(wo, &wi, sampler.Get2D(), &pdf,
BSDF_ALL, &flags);
if (f.IsBlack() || pdf == 0.f) break;
alpha *= f * AbsDot(wi, isect.shading.n) / pdf;
Assert(std::isinf(alpha.y()) == false);
specularBounce = (flags & BSDF_SPECULAR) != 0;
ray = isect.SpawnRay(wi);
// Account for attenuated subsurface scattering, if applicable
if (isect.bssrdf && (flags & BSDF_TRANSMISSION)) {
// Importance sample the BSSRDF
SurfaceInteraction pi;
Spectrum S = isect.bssrdf->Sample_S(
scene, sampler.Get1D(), sampler.Get2D(), arena, &pi, &pdf);
#ifndef NDEBUG
Assert(std::isinf(alpha.y()) == false);
#endif
if (S.IsBlack() || pdf == 0) break;
alpha *= S / pdf;
// Account for the attenuated direct subsurface scattering
// component
L += alpha *
UniformSampleOneLight(pi, scene, sampler, arena, true);
// Account for the indirect subsurface scattering component
Spectrum f = pi.bsdf->Sample_f(pi.wo, &wi, sampler.Get2D(),
&pdf, BSDF_ALL, &flags);
if (f.IsBlack() || pdf == 0.f) break;
alpha *= f * AbsDot(wi, pi.shading.n) / pdf;
#ifndef NDEBUG
Assert(std::isinf(alpha.y()) == false);
#endif
specularBounce = (flags & BSDF_SPECULAR) != 0;
ray = pi.SpawnRay(wi);
}
}
// Possibly terminate the path
if (bounces > 3) {
Float continueProbability = std::min((Float).5, alpha.y());
if (sampler.Get1D() > continueProbability) break;
alpha /= continueProbability;
Assert(std::isinf(alpha.y()) == false);
}
}
return L;
}
// PathIntegrator Method Definitions
Spectrum PathIntegrator::Li(const RayDifferential &r, const Scene &scene,
Sampler &sampler, MemoryArena &arena) const {
Spectrum L(0.f);
// Declare common path integration variables
RayDifferential ray(r);
Spectrum pathThroughput = Spectrum(1.f);
bool specularBounce = false;
for (int bounces = 0;; ++bounces) {
// Store intersection into _isect_
SurfaceInteraction isect;
bool foundIntersection = scene.Intersect(ray, &isect);
// Possibly add emitted light and terminate
if (bounces == 0 || specularBounce) {
// Add emitted light at path vertex or from the environment
if (foundIntersection)
L += pathThroughput * isect.Le(-ray.d);
else
for (const auto &light : scene.lights)
L += pathThroughput * light->Le(ray);
}
if (!foundIntersection || bounces >= maxDepth) break;
// Compute scattering functions and skip over medium boundaries
isect.ComputeScatteringFunctions(ray, arena, true);
if (!isect.bsdf) {
ray = isect.SpawnRay(ray.d);
bounces--;
continue;
}
// Sample illumination from lights to find path contribution
L += pathThroughput *
UniformSampleOneLight(isect, scene, sampler, arena);
// Sample BSDF to get new path direction
Vector3f wo = -ray.d, wi;
Float pdf;
BxDFType flags;
Spectrum f = isect.bsdf->Sample_f(wo, &wi, sampler.Get2D(), &pdf,
BSDF_ALL, &flags);
if (f.IsBlack() || pdf == 0.f) break;
pathThroughput *= f * AbsDot(wi, isect.shading.n) / pdf;
#ifndef NDEBUG
Assert(std::isinf(pathThroughput.y()) == false);
#endif
specularBounce = (flags & BSDF_SPECULAR) != 0;
ray = isect.SpawnRay(wi);
// Account for subsurface scattering, if applicable
if (isect.bssrdf && (flags & BSDF_TRANSMISSION)) {
// Importance sample the BSSRDF
BSSRDFSample bssrdfSample;
bssrdfSample.uDiscrete = sampler.Get1D();
bssrdfSample.pos = sampler.Get2D();
SurfaceInteraction isect_out = isect;
pathThroughput *= isect.bssrdf->Sample_f(
isect_out, scene, ray.time, bssrdfSample, arena, &isect, &pdf);
#ifndef NDEBUG
Assert(std::isinf(pathThroughput.y()) == false);
#endif
if (pathThroughput.IsBlack()) break;
// Account for the direct subsurface scattering component
isect.wo = Vector3f(isect.shading.n);
// Sample illumination from lights to find path contribution
L += pathThroughput *
UniformSampleOneLight(isect, scene, sampler, arena);
// Account for the indirect subsurface scattering component
Spectrum f = isect.bsdf->Sample_f(isect.wo, &wi, sampler.Get2D(),
&pdf, BSDF_ALL, &flags);
if (f.IsBlack() || pdf == 0.f) break;
pathThroughput *= f * AbsDot(wi, isect.shading.n) / pdf;
#ifndef NDEBUG
Assert(std::isinf(pathThroughput.y()) == false);
#endif
specularBounce = (flags & BSDF_SPECULAR) != 0;
ray = isect.SpawnRay(wi);
}
// Possibly terminate the path
if (bounces > 3) {
Float continueProbability = std::min((Float).5, pathThroughput.y());
if (sampler.Get1D() > continueProbability) break;
pathThroughput /= continueProbability;
Assert(std::isinf(pathThroughput.y()) == false);
}
}
return L;
}
Spectrum IrradianceCache::IndirectLo(const Point &p,
const Normal &n, const Vector &wo, BSDF *bsdf,
BxDFType flags, const Sample *sample,
const Scene *scene) const {
if (bsdf->NumComponents(flags) == 0)
return Spectrum(0.);
Spectrum E;
if (!InterpolateIrradiance(scene, p, n, &E)) {
// Compute irradiance at current point
u_int scramble[2] = { RandomUInt(), RandomUInt() };
float sumInvDists = 0.;
for (int i = 0; i < nSamples; ++i) {
// Trace ray to sample radiance for irradiance estimate
// Update irradiance statistics for rays traced
static StatsCounter nIrradiancePaths("Irradiance Cache",
"Paths followed for irradiance estimates");
++nIrradiancePaths;
float u[2];
Sample02(i, scramble, u);
Vector w = CosineSampleHemisphere(u[0], u[1]);
RayDifferential r(p, bsdf->LocalToWorld(w));
if (Dot(r.d, n) < 0) r.d = -r.d;
Spectrum L(0.);
// Do path tracing to compute radiance along ray for estimate
{
// Declare common path integration variables
Spectrum pathThroughput = 1.;
RayDifferential ray(r);
bool specularBounce = false;
for (int pathLength = 0; ; ++pathLength) {
// Find next vertex of path
Intersection isect;
if (!scene->Intersect(ray, &isect))
break;
if (pathLength == 0)
r.maxt = ray.maxt;
pathThroughput *= scene->Transmittance(ray);
// Possibly add emitted light at path vertex
if (specularBounce)
L += pathThroughput * isect.Le(-ray.d);
// Evaluate BSDF at hit point
BSDF *bsdf = isect.GetBSDF(ray);
// Sample illumination from lights to find path contribution
const Point &p = bsdf->dgShading.p;
const Normal &n = bsdf->dgShading.nn;
Vector wo = -ray.d;
L += pathThroughput *
UniformSampleOneLight(scene, p, n, wo, bsdf, sample);
if (pathLength+1 == maxIndirectDepth) break;
// Sample BSDF to get new path direction
// Get random numbers for sampling new direction, \mono{bs1}, \mono{bs2}, and \mono{bcs}
float bs1 = RandomFloat(), bs2 = RandomFloat(), bcs = RandomFloat();
Vector wi;
float pdf;
BxDFType flags;
Spectrum f = bsdf->Sample_f(wo, &wi, bs1, bs2, bcs,
&pdf, BSDF_ALL, &flags);
if (f.Black() || pdf == 0.)
break;
specularBounce = (flags & BSDF_SPECULAR) != 0;
pathThroughput *= f * AbsDot(wi, n) / pdf;
ray = RayDifferential(p, wi);
// Possibly terminate the path
if (pathLength > 3) {
float continueProbability = .5f;
if (RandomFloat() > continueProbability)
break;
pathThroughput /= continueProbability;
}
}
}
E += L;
float dist = r.maxt * r.d.Length();
sumInvDists += 1.f / dist;
}
E *= M_PI / float(nSamples);
// Add computed irradiance value to cache
// Update statistics for new irradiance sample
static StatsCounter nSamplesComputed("Irradiance Cache",
"Irradiance estimates computed");
++nSamplesComputed;
// Compute bounding box of irradiance sample's contribution region
static float minMaxDist =
.001f * powf(scene->WorldBound().Volume(), 1.f/3.f);
static float maxMaxDist =
.125f * powf(scene->WorldBound().Volume(), 1.f/3.f);
float maxDist = nSamples / sumInvDists;
if (minMaxDist > 0.f)
maxDist = Clamp(maxDist, minMaxDist, maxMaxDist);
maxDist *= maxError;
BBox sampleExtent(p);
sampleExtent.Expand(maxDist);
octree->Add(IrradianceSample(E, p, n, maxDist),
sampleExtent);
}
return .5f * bsdf->rho(wo, flags) * E;
}
Spectrum PathIntegrator::Li(const Scene *scene, const Renderer *renderer,
const RayDifferential &r, const Intersection &isect,
const Sample *sample, MemoryArena &arena) const {
// Declare common path integration variables
Spectrum pathThroughput = 1., L = 0.;
RayDifferential ray(r);
bool specularBounce = false;
Intersection localIsect;
const Intersection *isectp = &isect;
for (int pathLength = 0; ; ++pathLength) {
// Possibly add emitted light at path vertex
if (pathLength == 0 || specularBounce)
L += pathThroughput * isectp->Le(-ray.d);
// Sample illumination from lights to find path contribution
BSDF *bsdf = isectp->GetBSDF(ray, arena);
const Point &p = bsdf->dgShading.p;
const Normal &n = bsdf->dgShading.nn;
Vector wo = -ray.d;
if (pathLength < SAMPLE_DEPTH)
L += pathThroughput *
UniformSampleOneLight(scene, renderer, arena, p, n, wo,
isectp->RayEpsilon, bsdf, sample, lightNumOffset[pathLength],
&lightSampleOffsets[pathLength], &bsdfSampleOffsets[pathLength]);
else
L += pathThroughput *
UniformSampleOneLight(scene, renderer, arena, p, n, wo,
isectp->RayEpsilon, bsdf, sample);
// Sample BSDF to get new path direction
// Get _outgoingBSDFSample_ for sampling new path direction
BSDFSample outgoingBSDFSample;
if (pathLength < SAMPLE_DEPTH)
outgoingBSDFSample = BSDFSample(sample, pathSampleOffsets[pathLength], 0);
else
outgoingBSDFSample = BSDFSample(*sample->rng);
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;
pathThroughput *= f * AbsDot(wi, n) / pdf;
ray = RayDifferential(p, wi, ray, isectp->RayEpsilon);
// Possibly terminate the path
if (pathLength > 3) {
float continueProbability = min(.5f, pathThroughput.y());
if (sample->rng->RandomFloat() > continueProbability)
break;
pathThroughput /= continueProbability;
}
if (pathLength == maxDepth)
break;
// Find next vertex of path
if (!scene->Intersect(ray, &localIsect)) {
if (specularBounce) {
for (u_int i = 0; i < scene->lights.size(); ++i)
L += pathThroughput * scene->lights[i]->Le(ray);
}
break;
}
if (pathLength > 1)
pathThroughput *= renderer->Transmittance(scene, ray, NULL, arena, sample->rng);
isectp = &localIsect;
}
return L;
}
Spectrum VolPathIntegrator::Li(const RayDifferential &r, const Scene &scene,
Sampler &sampler, MemoryArena &arena,
int depth) const {
ProfilePhase p(Prof::SamplerIntegratorLi);
Spectrum L(0.f), beta(1.f);
RayDifferential ray(r);
bool specularBounce = false;
int bounces;
// Added after book publication: etaScale tracks the accumulated effect
// of radiance scaling due to rays passing through refractive
// boundaries (see the derivation on p. 527 of the third edition). We
// track this value in order to remove it from beta when we apply
// Russian roulette; this is worthwhile, since it lets us sometimes
// avoid terminating refracted rays that are about to be refracted back
// out of a medium and thus have their beta value increased.
Float etaScale = 1;
for (bounces = 0;; ++bounces) {
// Intersect _ray_ with scene and store intersection in _isect_
SurfaceInteraction isect;
bool foundIntersection = scene.Intersect(ray, &isect);
// Sample the participating medium, if present
MediumInteraction mi;
if (ray.medium) beta *= ray.medium->Sample(ray, sampler, arena, &mi);
if (beta.IsBlack()) break;
// Handle an interaction with a medium or a surface
if (mi.IsValid()) {
// Terminate path if ray escaped or _maxDepth_ was reached
if (bounces >= maxDepth) break;
++volumeInteractions;
// Handle scattering at point in medium for volumetric path tracer
const Distribution1D *lightDistrib =
lightDistribution->Lookup(mi.p);
L += beta * UniformSampleOneLight(mi, scene, arena, sampler, true,
lightDistrib);
Vector3f wo = -ray.d, wi;
mi.phase->Sample_p(wo, &wi, sampler.Get2D());
ray = mi.SpawnRay(wi);
} else {
++surfaceInteractions;
// Handle scattering at point on surface for volumetric path tracer
// Possibly add emitted light at intersection
if (bounces == 0 || specularBounce) {
// Add emitted light at path vertex or from the environment
if (foundIntersection)
L += beta * isect.Le(-ray.d);
else
for (const auto &light : scene.infiniteLights)
L += beta * light->Le(ray);
}
// Terminate path if ray escaped or _maxDepth_ was reached
if (!foundIntersection || bounces >= maxDepth) break;
// Compute scattering functions and skip over medium boundaries
isect.ComputeScatteringFunctions(ray, arena, true);
if (!isect.bsdf) {
ray = isect.SpawnRay(ray.d);
bounces--;
continue;
}
// Sample illumination from lights to find attenuated path
// contribution
const Distribution1D *lightDistrib =
lightDistribution->Lookup(isect.p);
L += beta * UniformSampleOneLight(isect, scene, arena, sampler,
true, lightDistrib);
// Sample BSDF to get new path direction
Vector3f wo = -ray.d, wi;
Float pdf;
BxDFType flags;
Spectrum f = isect.bsdf->Sample_f(wo, &wi, sampler.Get2D(), &pdf,
BSDF_ALL, &flags);
if (f.IsBlack() || pdf == 0.f) break;
beta *= f * AbsDot(wi, isect.shading.n) / pdf;
DCHECK(std::isinf(beta.y()) == false);
specularBounce = (flags & BSDF_SPECULAR) != 0;
if ((flags & BSDF_SPECULAR) && (flags & BSDF_TRANSMISSION)) {
Float eta = isect.bsdf->eta;
// Update the term that tracks radiance scaling for refraction
// depending on whether the ray is entering or leaving the
// medium.
etaScale *=
(Dot(wo, isect.n) > 0) ? (eta * eta) : 1 / (eta * eta);
}
ray = isect.SpawnRay(ray, wi, flags, isect.bsdf->eta);
// Account for attenuated subsurface scattering, if applicable
if (isect.bssrdf && (flags & BSDF_TRANSMISSION)) {
// Importance sample the BSSRDF
SurfaceInteraction pi;
Spectrum S = isect.bssrdf->Sample_S(
scene, sampler.Get1D(), sampler.Get2D(), arena, &pi, &pdf);
DCHECK(std::isinf(beta.y()) == false);
if (S.IsBlack() || pdf == 0) break;
beta *= S / pdf;
// Account for the attenuated direct subsurface scattering
// component
L += beta *
UniformSampleOneLight(pi, scene, arena, sampler, true,
lightDistribution->Lookup(pi.p));
// Account for the indirect subsurface scattering component
Spectrum f = pi.bsdf->Sample_f(pi.wo, &wi, sampler.Get2D(),
&pdf, BSDF_ALL, &flags);
if (f.IsBlack() || pdf == 0) break;
beta *= f * AbsDot(wi, pi.shading.n) / pdf;
DCHECK(std::isinf(beta.y()) == false);
specularBounce = (flags & BSDF_SPECULAR) != 0;
ray = pi.SpawnRay(wi);
}
}
// Possibly terminate the path with Russian roulette
// Factor out radiance scaling due to refraction in rrBeta.
Spectrum rrBeta = beta * etaScale;
if (rrBeta.MaxComponentValue() < rrThreshold && bounces > 3) {
Float q = std::max((Float).05, 1 - rrBeta.MaxComponentValue());
if (sampler.Get1D() < q) break;
beta /= 1 - q;
DCHECK(std::isinf(beta.y()) == false);
}
}
ReportValue(pathLength, bounces);
return L;
}
Spectrum DirectLighting::Li(const Scene *scene,
const RayDifferential &ray, const Sample *sample,
float *alpha) const {
Intersection isect;
Spectrum L(0.);
if (scene->Intersect(ray, &isect)) {
if (alpha) *alpha = 1.;
// Evaluate BSDF at hit point
BSDF *bsdf = isect.GetBSDF(ray);
Vector wo = -ray.d;
const Point &p = bsdf->dgShading.p;
const Normal &n = bsdf->dgShading.nn;
// Compute emitted light if ray hit an area light source
L += isect.Le(wo);
// Compute direct lighting for _DirectLighting_ integrator
if (scene->lights.size() > 0) {
// Apply direct lighting strategy
switch (strategy) {
case SAMPLE_ALL_UNIFORM:
L += UniformSampleAllLights(scene, p, n, wo, bsdf,
sample, lightSampleOffset, bsdfSampleOffset,
bsdfComponentOffset);
break;
case SAMPLE_ONE_UNIFORM:
L += UniformSampleOneLight(scene, p, n, wo, bsdf,
sample, lightSampleOffset[0], lightNumOffset,
bsdfSampleOffset[0], bsdfComponentOffset[0]);
break;
case SAMPLE_ONE_WEIGHTED:
L += WeightedSampleOneLight(scene, p, n, wo, bsdf,
sample, lightSampleOffset[0], lightNumOffset,
bsdfSampleOffset[0], bsdfComponentOffset[0], avgY,
avgYsample, cdf, overallAvgY);
break;
}
}
if (rayDepth++ < maxDepth) {
Vector wi;
// Trace rays for specular reflection and refraction
Spectrum f = bsdf->Sample_f(wo, &wi,
BxDFType(BSDF_REFLECTION | BSDF_SPECULAR));
if (!f.Black()) {
// Compute ray differential _rd_ for specular reflection
RayDifferential rd(p, wi);
rd.hasDifferentials = true;
rd.rx.o = p + isect.dg.dpdx;
rd.ry.o = p + isect.dg.dpdy;
// Compute differential reflected directions
Normal dndx = bsdf->dgShading.dndu * bsdf->dgShading.dudx +
bsdf->dgShading.dndv * bsdf->dgShading.dvdx;
Normal dndy = bsdf->dgShading.dndu * bsdf->dgShading.dudy +
bsdf->dgShading.dndv * bsdf->dgShading.dvdy;
Vector dwodx = -ray.rx.d - wo, dwody = -ray.ry.d - wo;
float dDNdx = Dot(dwodx, n) + Dot(wo, dndx);
float dDNdy = Dot(dwody, n) + Dot(wo, dndy);
rd.rx.d = wi -
dwodx + 2 * Vector(Dot(wo, n) * dndx +
dDNdx * n);
rd.ry.d = wi -
dwody + 2 * Vector(Dot(wo, n) * dndy +
dDNdy * n);
L += scene->Li(rd, sample) * f * AbsDot(wi, n);
}
f = bsdf->Sample_f(wo, &wi,
BxDFType(BSDF_TRANSMISSION | BSDF_SPECULAR));
if (!f.Black()) {
// Compute ray differential _rd_ for specular transmission
RayDifferential rd(p, wi);
rd.hasDifferentials = true;
rd.rx.o = p + isect.dg.dpdx;
rd.ry.o = p + isect.dg.dpdy;
float eta = bsdf->eta;
Vector w = -wo;
if (Dot(wo, n) < 0) eta = 1.f / eta;
Normal dndx = bsdf->dgShading.dndu * bsdf->dgShading.dudx + bsdf->dgShading.dndv * bsdf->dgShading.dvdx;
Normal dndy = bsdf->dgShading.dndu * bsdf->dgShading.dudy + bsdf->dgShading.dndv * bsdf->dgShading.dvdy;
Vector dwodx = -ray.rx.d - wo, dwody = -ray.ry.d - wo;
float dDNdx = Dot(dwodx, n) + Dot(wo, dndx);
float dDNdy = Dot(dwody, n) + Dot(wo, dndy);
float mu = eta * Dot(w, n) - Dot(wi, n);
float dmudx = (eta - (eta*eta*Dot(w,n))/Dot(wi, n)) * dDNdx;
float dmudy = (eta - (eta*eta*Dot(w,n))/Dot(wi, n)) * dDNdy;
rd.rx.d = wi + eta * dwodx - Vector(mu * dndx + dmudx * n);
rd.ry.d = wi + eta * dwody - Vector(mu * dndy + dmudy * n);
L += scene->Li(rd, sample) * f * AbsDot(wi, n);
}
}
--rayDepth;
}
else {
// Handle ray with no intersection
if (alpha) *alpha = 0.;
for (u_int i = 0; i < scene->lights.size(); ++i)
L += scene->lights[i]->Le(ray);
if (alpha && !L.Black()) *alpha = 1.;
return L;
}
return L;
}
// PathIntegrator Method Definitions
Spectrum PathIntegrator::Li(const RayDifferential &r, const Scene &scene,
Sampler &sampler, MemoryArena &arena,
int depth) const {
ProfilePhase p(Prof::SamplerIntegratorLi);
Spectrum L(0.f), beta(1.f);
RayDifferential ray(r);
bool specularBounce = false;
for (int bounces = 0;; ++bounces) {
// Find next path vertex and accumulate contribution
// Intersect _ray_ with scene and store intersection in _isect_
SurfaceInteraction isect;
bool foundIntersection = scene.Intersect(ray, &isect);
// Possibly add emitted light at intersection
if (bounces == 0 || specularBounce) {
// Add emitted light at path vertex or from the environment
if (foundIntersection)
L += beta * isect.Le(-ray.d);
else
for (const auto &light : scene.lights)
L += beta * light->Le(ray);
}
// Terminate path if ray escaped or _maxDepth_ was reached
if (!foundIntersection || bounces >= maxDepth) break;
// Compute scattering functions and skip over medium boundaries
isect.ComputeScatteringFunctions(ray, arena, true);
if (!isect.bsdf) {
ray = isect.SpawnRay(ray.d);
bounces--;
continue;
}
// Sample illumination from lights to find path contribution
L += beta * UniformSampleOneLight(isect, scene, arena, sampler);
// Sample BSDF to get new path direction
Vector3f wo = -ray.d, wi;
Float pdf;
BxDFType flags;
Spectrum f = isect.bsdf->Sample_f(wo, &wi, sampler.Get2D(), &pdf,
BSDF_ALL, &flags);
if (f.IsBlack() || pdf == 0.f) break;
beta *= f * AbsDot(wi, isect.shading.n) / pdf;
Assert(std::isinf(beta.y()) == false);
specularBounce = (flags & BSDF_SPECULAR) != 0;
ray = isect.SpawnRay(wi);
// Account for subsurface scattering, if applicable
if (isect.bssrdf && (flags & BSDF_TRANSMISSION)) {
// Importance sample the BSSRDF
SurfaceInteraction pi;
Spectrum S = isect.bssrdf->Sample_S(
scene, sampler.Get1D(), sampler.Get2D(), arena, &pi, &pdf);
#ifndef NDEBUG
Assert(std::isinf(beta.y()) == false);
#endif
if (S.IsBlack() || pdf == 0) break;
beta *= S / pdf;
// Account for the direct subsurface scattering component
L += beta * UniformSampleOneLight(pi, scene, arena, sampler);
// Account for the indirect subsurface scattering component
Spectrum f = pi.bsdf->Sample_f(pi.wo, &wi, sampler.Get2D(), &pdf,
BSDF_ALL, &flags);
if (f.IsBlack() || pdf == 0) break;
beta *= f * AbsDot(wi, pi.shading.n) / pdf;
#ifndef NDEBUG
Assert(std::isinf(beta.y()) == false);
#endif
specularBounce = (flags & BSDF_SPECULAR) != 0;
ray = pi.SpawnRay(wi);
}
// Possibly terminate the path with Russian roulette
if (bounces > 3) {
Float continueProbability = std::min((Float).95, beta.y());
if (sampler.Get1D() > continueProbability) break;
beta /= continueProbability;
Assert(std::isinf(beta.y()) == false);
}
}
return L;
}
Spectrum PathIntegrator::Li(const RayDifferential &r, const Scene &scene,
Sampler &sampler, MemoryArena &arena,
int depth) const {
ProfilePhase p(Prof::SamplerIntegratorLi);
Spectrum L(0.f), beta(1.f);
RayDifferential ray(r);
bool specularBounce = false;
int bounces;
for (bounces = 0;; ++bounces) {
// Find next path vertex and accumulate contribution
VLOG(2) << "Path tracer bounce " << bounces << ", current L = " << L <<
", beta = " << beta;
// Intersect _ray_ with scene and store intersection in _isect_
SurfaceInteraction isect;
bool foundIntersection = scene.Intersect(ray, &isect);
// Possibly add emitted light at intersection
if (bounces == 0 || specularBounce) {
// Add emitted light at path vertex or from the environment
if (foundIntersection) {
L += beta * isect.Le(-ray.d);
VLOG(2) << "Added Le -> L = " << L;
} else {
for (const auto &light : scene.infiniteLights)
L += beta * light->Le(ray);
VLOG(2) << "Added infinite area lights -> L = " << L;
}
}
// Terminate path if ray escaped or _maxDepth_ was reached
if (!foundIntersection || bounces >= maxDepth) break;
// Compute scattering functions and skip over medium boundaries
isect.ComputeScatteringFunctions(ray, arena, true);
if (!isect.bsdf) {
VLOG(2) << "Skipping intersection due to null bsdf";
ray = isect.SpawnRay(ray.d);
bounces--;
continue;
}
const Distribution1D *distrib = lightDistribution->Lookup(isect.p);
// Sample illumination from lights to find path contribution.
// (But skip this for perfectly specular BSDFs.)
if (isect.bsdf->NumComponents(BxDFType(BSDF_ALL & ~BSDF_SPECULAR)) >
0) {
++totalPaths;
Spectrum Ld =
beta * UniformSampleOneLight(isect, scene, arena, sampler, false,
distrib);
VLOG(2) << "Sampled direct lighting Ld = " << Ld;
if (Ld.IsBlack()) ++zeroRadiancePaths;
CHECK_GE(Ld.y(), 0.f);
L += Ld;
}
// Sample BSDF to get new path direction
Vector3f wo = -ray.d, wi;
Float pdf;
BxDFType flags;
Spectrum f = isect.bsdf->Sample_f(wo, &wi, sampler.Get2D(), &pdf,
BSDF_ALL, &flags);
VLOG(2) << "Sampled BSDF, f = " << f << ", pdf = " << pdf;
if (f.IsBlack() || pdf == 0.f) break;
beta *= f * AbsDot(wi, isect.shading.n) / pdf;
VLOG(2) << "Updated beta = " << beta;
CHECK_GE(beta.y(), 0.f);
DCHECK(!std::isinf(beta.y()));
specularBounce = (flags & BSDF_SPECULAR) != 0;
ray = isect.SpawnRay(wi);
// Account for subsurface scattering, if applicable
if (isect.bssrdf && (flags & BSDF_TRANSMISSION)) {
// Importance sample the BSSRDF
SurfaceInteraction pi;
Spectrum S = isect.bssrdf->Sample_S(
scene, sampler.Get1D(), sampler.Get2D(), arena, &pi, &pdf);
DCHECK(!std::isinf(beta.y()));
if (S.IsBlack() || pdf == 0) break;
beta *= S / pdf;
// Account for the direct subsurface scattering component
L += beta * UniformSampleOneLight(pi, scene, arena, sampler, false,
lightDistribution->Lookup(pi.p));
// Account for the indirect subsurface scattering component
Spectrum f = pi.bsdf->Sample_f(pi.wo, &wi, sampler.Get2D(), &pdf,
BSDF_ALL, &flags);
if (f.IsBlack() || pdf == 0) break;
beta *= f * AbsDot(wi, pi.shading.n) / pdf;
DCHECK(!std::isinf(beta.y()));
specularBounce = (flags & BSDF_SPECULAR) != 0;
ray = pi.SpawnRay(wi);
}
// Possibly terminate the path with Russian roulette
if (beta.y() < rrThreshold && bounces > 3) {
Float q = std::max((Float).05, 1 - beta.MaxComponentValue());
VLOG(2) << "RR termination probability q = " << q;
if (sampler.Get1D() < q) break;
beta /= 1 - q;
VLOG(2) << "After RR survival, beta = " << beta;
DCHECK(!std::isinf(beta.y()));
}
}
ReportValue(pathLength, bounces);
return L;
}