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提交 d19ed715 编写于 作者: M Matt Pharr
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Update from book source. No functional changes. 

Assorted renamings in the VolPathIntegrator implementation.
上级 fb5ed5d6
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Showing with 70 addition and 66 deletion
src/pbrt/cpu/integrators.cpp
浏览文件 @ d19ed715
......@@ -950,7 +950,7 @@ SampledSpectrum VolPathIntegrator::Li(RayDifferential ray, SampledWavelengths &l
Sampler sampler, ScratchBuffer &scratchBuffer,
VisibleSurface *visibleSurf) const {
// Declare state variables for volumetric path sampling
SampledSpectrum L(0.f), beta(1.f), inv_w_u(1.f), inv_w_l(1.f);
SampledSpectrum L(0.f), beta(1.f), r_u(1.f), r_l(1.f);
bool specularBounce = false, anyNonSpecularBounces = false;
int depth = 0;
Float etaScale = 1;
......@@ -984,16 +984,16 @@ SampledSpectrum VolPathIntegrator::Li(RayDifferential ray, SampledWavelengths &l
++volumeInteractions;
// Add emission from medium scattering event
if (depth < maxDepth && mp.Le) {
// Compute $\hat{P}$ at new path vertex
// Compute $\beta'$ at new path vertex
Float pdf = sigma_maj[0] * T_maj[0];
SampledSpectrum betap = beta * T_maj * mp.sigma_a / pdf;
SampledSpectrum betap = beta * T_maj / pdf;
// Compute PDF for absorption at path vertex
SampledSpectrum inv_w_e = inv_w_u * sigma_maj * T_maj / pdf;
// Compute rescaled path probability for absorption at path vertex
SampledSpectrum r_e = r_u * sigma_maj * T_maj / pdf;
// Update _L_ for medium emission
if (inv_w_e)
L += betap * mp.Le / inv_w_e.Average();
if (r_e)
L += betap * mp.sigma_a * mp.Le / r_e.Average();
}
// Compute medium event probabilities for interaction
......@@ -1018,14 +1018,16 @@ SampledSpectrum VolPathIntegrator::Li(RayDifferential ray, SampledWavelengths &l
return false;
}
// Update _beta_ and _r_u_ for real scattering event
Float pdf = T_maj[0] * mp.sigma_s[0];
beta *= T_maj * mp.sigma_s / pdf;
inv_w_u *= T_maj * mp.sigma_s / pdf;
if (beta && inv_w_u) {
r_u *= T_maj * mp.sigma_s / pdf;
if (beta && r_u) {
// Sample direct lighting at volume scattering event
MediumInteraction intr(p, -ray.d, ray.time, ray.medium,
mp.phase);
L += SampleLd(intr, nullptr, lambda, sampler, beta, inv_w_u);
L += SampleLd(intr, nullptr, lambda, sampler, beta, r_u);
// Sample new direction at real scattering event
Point2f u = sampler.Get2D();
......@@ -1036,7 +1038,7 @@ SampledSpectrum VolPathIntegrator::Li(RayDifferential ray, SampledWavelengths &l
else {
// Update ray path state for indirect volume scattering
beta *= ps->p / ps->pdf;
inv_w_l = inv_w_u / ps->pdf;
r_l = r_u / ps->pdf;
prevIntrContext = LightSampleContext(intr);
scattered = true;
ray.o = p;
......@@ -1053,19 +1055,20 @@ SampledSpectrum VolPathIntegrator::Li(RayDifferential ray, SampledWavelengths &l
ClampZero(sigma_maj - mp.sigma_a - mp.sigma_s);
Float pdf = T_maj[0] * sigma_n[0];
beta *= T_maj * sigma_n / pdf;
inv_w_u *= T_maj * sigma_n / pdf;
inv_w_l *= T_maj * sigma_maj / pdf;
return beta && inv_w_u;
r_u *= T_maj * sigma_n / pdf;
r_l *= T_maj * sigma_maj / pdf;
return beta && r_u;
}
});
// Handle terminated, scattered, and unscattered rays after medium sampling
if (terminated || !beta || !inv_w_u)
// Handle terminated, scattered, and unscattered medium rays
if (terminated || !beta || !r_u)
return L;
if (scattered)
continue;
beta *= T_maj / T_maj[0];
inv_w_u *= T_maj / T_maj[0];
inv_w_l *= T_maj / T_maj[0];
r_u *= T_maj / T_maj[0];
r_l *= T_maj / T_maj[0];
}
// Handle surviving unscattered rays
// Add emitted light at volume path vertex or from the environment
......@@ -1074,13 +1077,13 @@ SampledSpectrum VolPathIntegrator::Li(RayDifferential ray, SampledWavelengths &l
for (const auto &light : infiniteLights) {
if (SampledSpectrum Le = light.Le(ray, lambda); Le) {
if (depth == 0 || specularBounce)
L += beta * Le / inv_w_u.Average();
L += beta * Le / r_u.Average();
else {
// Add infinite light contribution using both PDFs with MIS
Float lightPDF = lightSampler.PMF(prevIntrContext, light) *
light.PDF_Li(prevIntrContext, ray.d, true);
inv_w_l *= lightPDF;
L += beta * Le / (inv_w_u + inv_w_l).Average();
r_l *= lightPDF;
L += beta * Le / (r_u + r_l).Average();
}
}
}
......@@ -1091,14 +1094,14 @@ SampledSpectrum VolPathIntegrator::Li(RayDifferential ray, SampledWavelengths &l
if (SampledSpectrum Le = isect.Le(-ray.d, lambda); Le) {
// Add contribution of emission from intersected surface
if (depth == 0 || specularBounce)
L += beta * Le / inv_w_u.Average();
L += beta * Le / r_u.Average();
else {
// Add surface light contribution using both PDFs with MIS
Light areaLight(isect.areaLight);
Float lightPDF = lightSampler.PMF(prevIntrContext, areaLight) *
areaLight.PDF_Li(prevIntrContext, ray.d, true);
inv_w_l *= lightPDF;
L += beta * Le / (inv_w_u + inv_w_l).Average();
r_l *= lightPDF;
L += beta * Le / (r_u + r_l).Average();
}
}
......@@ -1146,7 +1149,7 @@ SampledSpectrum VolPathIntegrator::Li(RayDifferential ray, SampledWavelengths &l
// Sample illumination from lights to find attenuated path contribution
if (IsNonSpecular(bsdf.Flags())) {
L += SampleLd(isect, &bsdf, lambda, sampler, beta, inv_w_u);
L += SampleLd(isect, &bsdf, lambda, sampler, beta, r_u);
DCHECK(IsInf(L.y(lambda)) == false);
}
prevIntrContext = LightSampleContext(isect);
......@@ -1157,12 +1160,12 @@ SampledSpectrum VolPathIntegrator::Li(RayDifferential ray, SampledWavelengths &l
pstd::optional<BSDFSample> bs = bsdf.Sample_f(wo, u, sampler.Get2D());
if (!bs)
break;
// Update _T_hat_ and PDFs for BSDF scattering
// Update _beta_ and rescaled path probabilities for BSDF scattering
beta *= bs->f * AbsDot(bs->wi, isect.shading.n) / bs->pdf;
if (bs->pdfIsProportional)
inv_w_l = inv_w_u / bsdf.PDF(wo, bs->wi);
r_l = r_u / bsdf.PDF(wo, bs->wi);
else
inv_w_l = inv_w_u / bs->pdf;
r_l = r_u / bs->pdf;
PBRT_DBG("%s\n", StringPrintf("Sampled BSDF, f = %s, pdf = %f -> beta = %s",
bs->f, bs->pdf, beta)
......@@ -1215,7 +1218,7 @@ SampledSpectrum VolPathIntegrator::Li(RayDifferential ray, SampledWavelengths &l
// Update path state for subsurface scattering
Float pdf = interactionSampler.SampleProbability() * bssrdfSample.pdf[0];
beta *= bssrdfSample.Sp / pdf;
inv_w_u *= bssrdfSample.pdf / bssrdfSample.pdf[0];
r_u *= bssrdfSample.pdf / bssrdfSample.pdf[0];
SurfaceInteraction pi = ssi;
pi.wo = bssrdfSample.wo;
prevIntrContext = LightSampleContext(pi);
......@@ -1229,7 +1232,7 @@ SampledSpectrum VolPathIntegrator::Li(RayDifferential ray, SampledWavelengths &l
++totalBSDFs;
// Account for attenuated direct illumination subsurface scattering
L += SampleLd(pi, &Sw, lambda, sampler, beta, inv_w_u);
L += SampleLd(pi, &Sw, lambda, sampler, beta, r_u);
// Sample ray for indirect subsurface scattering
Float u = sampler.Get1D();
......@@ -1237,7 +1240,7 @@ SampledSpectrum VolPathIntegrator::Li(RayDifferential ray, SampledWavelengths &l
if (!bs)
break;
beta *= bs->f * AbsDot(bs->wi, pi.shading.n) / bs->pdf;
inv_w_l = inv_w_u / bs->pdf;
r_l = r_u / bs->pdf;
// Don't increment depth this time...
DCHECK(!IsInf(beta.y(lambda)));
specularBounce = bs->IsSpecular();
......@@ -1247,7 +1250,7 @@ SampledSpectrum VolPathIntegrator::Li(RayDifferential ray, SampledWavelengths &l
// Possibly terminate volumetric path with Russian roulette
if (!beta)
break;
SampledSpectrum rrBeta = beta * etaScale / inv_w_u.Average();
SampledSpectrum rrBeta = beta * etaScale / r_u.Average();
Float uRR = sampler.Get1D();
PBRT_DBG("%s\n",
StringPrintf("etaScale %f -> rrBeta %s", etaScale, rrBeta).c_str());
......@@ -1264,7 +1267,7 @@ SampledSpectrum VolPathIntegrator::Li(RayDifferential ray, SampledWavelengths &l
SampledSpectrum VolPathIntegrator::SampleLd(const Interaction &intr, const BSDF *bsdf,
SampledWavelengths &lambda, Sampler sampler,
SampledSpectrum beta,
SampledSpectrum inv_w_p) const {
SampledSpectrum r_p) const {
// Estimate light-sampled direct illumination at _intr_
// Initialize _LightSampleContext_ for volumetric light sampling
LightSampleContext ctx;
......@@ -1316,7 +1319,7 @@ SampledSpectrum VolPathIntegrator::SampleLd(const Interaction &intr, const BSDF
// Declare path state variables for ray to light source
Ray lightRay = intr.SpawnRayTo(ls->pLight);
SampledSpectrum T_ray(1.f), inv_w_l(1.f), inv_w_u(1.f);
SampledSpectrum T_ray(1.f), r_l(1.f), r_u(1.f);
RNG rng(Hash(lightRay.o), Hash(lightRay.d));
while (lightRay.d != Vector3f(0, 0, 0)) {
......@@ -1330,37 +1333,38 @@ SampledSpectrum VolPathIntegrator::SampleLd(const Interaction &intr, const BSDF
if (lightRay.medium) {
Float tMax = si ? si->tHit : (1 - ShadowEpsilon);
Float u = rng.Uniform<Float>();
SampledSpectrum T_maj = SampleT_maj(
lightRay, tMax, u, rng, lambda,
[&](Point3f p, MediumProperties mp, SampledSpectrum sigma_maj,
SampledSpectrum T_maj) {
// Update ray transmittance estimate at sampled point
// Update _T_ray_ and PDFs using ratio-tracking estimator
SampledSpectrum sigma_n =
ClampZero(sigma_maj - mp.sigma_a - mp.sigma_s);
Float pdf = T_maj[0] * sigma_maj[0];
T_ray *= T_maj * sigma_n / pdf;
inv_w_l *= T_maj * sigma_maj / pdf;
inv_w_u *= T_maj * sigma_n / pdf;
// Possibly terminate transmittance computation using Russian roulette
SampledSpectrum Tr = T_ray / (inv_w_l + inv_w_u).Average();
if (Tr.MaxComponentValue() < 0.05f) {
Float q = 0.75f;
if (rng.Uniform<Float>() < q)
T_ray = SampledSpectrum(0.);
else
T_ray /= 1 - q;
}
SampledSpectrum T_maj =
SampleT_maj(lightRay, tMax, u, rng, lambda,
[&](Point3f p, MediumProperties mp, SampledSpectrum sigma_maj,
SampledSpectrum T_maj) {
// Update ray transmittance estimate at sampled point
// Update _T_ray_ and PDFs using ratio-tracking estimator
SampledSpectrum sigma_n =
ClampZero(sigma_maj - mp.sigma_a - mp.sigma_s);
Float pdf = T_maj[0] * sigma_maj[0];
T_ray *= T_maj * sigma_n / pdf;
r_l *= T_maj * sigma_maj / pdf;
r_u *= T_maj * sigma_n / pdf;
// Possibly terminate transmittance computation using
// Russian roulette
SampledSpectrum Tr = T_ray / (r_l + r_u).Average();
if (Tr.MaxComponentValue() < 0.05f) {
Float q = 0.75f;
if (rng.Uniform<Float>() < q)
T_ray = SampledSpectrum(0.);
else
T_ray /= 1 - q;
}
if (!T_ray)
return false;
return true;
});
if (!T_ray)
return false;
return true;
});
// Update transmittance estimate for final segment
T_ray *= T_maj / T_maj[0];
inv_w_l *= T_maj / T_maj[0];
inv_w_u *= T_maj / T_maj[0];
r_l *= T_maj / T_maj[0];
r_u *= T_maj / T_maj[0];
}
// Generate next ray segment or return final transmittance
......@@ -1371,12 +1375,12 @@ SampledSpectrum VolPathIntegrator::SampleLd(const Interaction &intr, const BSDF
lightRay = si->intr.SpawnRayTo(ls->pLight);
}
// Return path contribution function estimate for direct lighting
inv_w_l *= inv_w_p * lightPDF;
inv_w_u *= inv_w_p * scatterPDF;
r_l *= r_p * lightPDF;
r_u *= r_p * scatterPDF;
if (IsDeltaLight(light.Type()))
return beta * f_hat * T_ray * ls->L / inv_w_l.Average();
return beta * f_hat * T_ray * ls->L / r_l.Average();
else
return beta * f_hat * T_ray * ls->L / (inv_w_l + inv_w_u).Average();
return beta * f_hat * T_ray * ls->L / (r_l + r_u).Average();
}
std::string VolPathIntegrator::ToString() const {
......
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