Vec3f TraceBase::volumeLightSample(PathSampleGenerator &sampler,
MediumSample &mediumSample,
const Primitive &light,
const Medium *medium,
int bounce,
const Ray &parentRay)
{
LightSample lightSample;
if (!light.sampleDirect(_threadId, mediumSample.p, sampler, lightSample))
return Vec3f(0.0f);
Vec3f f = mediumSample.phase->eval(parentRay.dir(), lightSample.d);
if (f == 0.0f)
return Vec3f(0.0f);
Ray ray = parentRay.scatter(mediumSample.p, lightSample.d, 0.0f);
ray.setPrimaryRay(false);
IntersectionTemporary data;
IntersectionInfo info;
Vec3f e = attenuatedEmission(sampler, light, medium, lightSample.dist, data, info, bounce, false, ray, nullptr);
if (e == 0.0f)
return Vec3f(0.0f);
Vec3f lightF = f*e/lightSample.pdf;
if (!light.isDirac())
lightF *= SampleWarp::powerHeuristic(lightSample.pdf, mediumSample.phase->pdf(parentRay.dir(), lightSample.d));
return lightF;
}
Vec3f TraceBase::attenuatedEmission(PathSampleGenerator &sampler,
const Primitive &light,
const Medium *medium,
float expectedDist,
IntersectionTemporary &data,
IntersectionInfo &info,
int bounce,
bool startsOnSurface,
Ray &ray,
Vec3f *transmittance)
{
CONSTEXPR float fudgeFactor = 1.0f + 1e-3f;
if (light.isDirac()) {
ray.setFarT(expectedDist);
} else {
if (!light.intersect(ray, data) || ray.farT()*fudgeFactor < expectedDist)
return Vec3f(0.0f);
}
info.p = ray.pos() + ray.dir()*ray.farT();
info.w = ray.dir();
light.intersectionInfo(data, info);
Vec3f shadow = generalizedShadowRay(sampler, ray, medium, &light, startsOnSurface, true, bounce);
if (transmittance)
*transmittance = shadow;
if (shadow == 0.0f)
return Vec3f(0.0f);
return shadow*light.evalDirect(data, info);
}
Vec3f TraceBase::volumeSampleDirect(const Primitive &light,
PathSampleGenerator &sampler,
MediumSample &mediumSample,
const Medium *medium,
int bounce,
const Ray &parentRay)
{
Vec3f result = volumeLightSample(sampler, mediumSample, light, medium, bounce, parentRay);
if (!light.isDirac())
result += volumePhaseSample(light, sampler, mediumSample, medium, bounce, parentRay);
return result;
}
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;
}
Vec3f TraceBase::lightSample(const Primitive &light,
SurfaceScatterEvent &event,
const Medium *medium,
int bounce,
const Ray &parentRay,
Vec3f *transmittance)
{
LightSample sample;
if (!light.sampleDirect(_threadId, event.info->p, *event.sampler, sample))
return Vec3f(0.0f);
event.wo = event.frame.toLocal(sample.d);
if (!isConsistent(event, sample.d))
return Vec3f(0.0f);
bool geometricBackside = (sample.d.dot(event.info->Ng) < 0.0f);
medium = event.info->primitive->selectMedium(medium, geometricBackside);
event.requestedLobe = BsdfLobes::AllButSpecular;
Vec3f f = event.info->bsdf->eval(event, false);
if (f == 0.0f)
return Vec3f(0.0f);
Ray ray = parentRay.scatter(event.info->p, sample.d, event.info->epsilon);
ray.setPrimaryRay(false);
IntersectionTemporary data;
IntersectionInfo info;
Vec3f e = attenuatedEmission(*event.sampler, light, medium, sample.dist, data, info, bounce, true, ray, transmittance);
if (e == 0.0f)
return Vec3f(0.0f);
Vec3f lightF = f*e/sample.pdf;
if (!light.isDirac())
lightF *= SampleWarp::powerHeuristic(sample.pdf, event.info->bsdf->pdf(event));
return lightF;
}
