Color3f Li(const Scene *scene, Sampler *sampler, const Ray3f &r) const {
/* Find the surface that is visible in the requested direction */
Intersection its;
Ray3f ray(r);
if (!scene->rayIntersect(ray, its))
return Color3f(0.0f);
Color3f radiance(0.0f);
bool specularBounce = false;
Color3f pathThroughput(1.0f);
for ( int bounces = 0; ; ++bounces ) {
const Luminaire* luminaire = its.mesh->getLuminaire();
if ((bounces == 0 || specularBounce) && luminaire != NULL) {
Vector3f wo = (-ray.d).normalized();
Color3f emission = luminaire->le(its.p, its.shFrame.n, wo);
radiance += pathThroughput*emission;
}
const Texture* texture = its.mesh->getTexture();
Color3f texel(1.0f);
if ( texture ) {
texel = texture->lookUp(its.uv.x(), its.uv.y());
}
const BSDF* bsdf = its.mesh->getBSDF();
// sample illumination from lights, add to path contribution
if (!bsdf->isSpecular()){
radiance += pathThroughput*UniformSampleAllLights(scene, ray, its, sampler, m_samplePolicy)*texel;
}
// sample bsdf to get new path direction
BSDFQueryRecord bRec(its.toLocal((-ray.d)).normalized());
Color3f f = bsdf->sample(bRec, sampler->next2D() );
if (f.isZero() ) { // farther path no contribution
break;
}
specularBounce = bsdf->isSpecular();
Vector3f d = its.toWorld(bRec.wo);
f *= texel;
pathThroughput *= f;
ray = Ray3f(its.p, d );
// possibly termination
if (bounces > kSampleDepth) {
#if 0
float continueProbability = std::min( 0.5f, pathThroughput.y() );
if ( sampler->next1D() > continueProbability ) {
break;
}
#else
float continueProbability = std::max(f.x(),
std::max(f.y(), f.z()));
if ( sampler->next1D() > continueProbability ) {
break;
}
#endif
pathThroughput /= continueProbability;
}
if (bounces == m_maxDepth) {
break;
}
// find next vertex of path
if ( !scene->rayIntersect(ray, its) ) {
break;
}
}
return radiance;
}
