Vec3f RoughPlasticBsdf::eval(const SurfaceScatterEvent &event) const
{
bool sampleR = event.requestedLobe.test(BsdfLobes::GlossyReflectionLobe);
bool sampleT = event.requestedLobe.test(BsdfLobes::DiffuseReflectionLobe);
if (!sampleR && !sampleT)
return Vec3f(0.0f);
if (event.wi.z() <= 0.0f || event.wo.z() <= 0.0f)
return Vec3f(0.0f);
Vec3f glossyR(0.0f);
if (sampleR)
glossyR = RoughDielectricBsdf::evalBase(event, true, false, (*_roughness)[*event.info].x(), _ior, _distribution);
Vec3f diffuseR(0.0f);
if (sampleT) {
float eta = 1.0f/_ior;
float Fi = Fresnel::dielectricReflectance(eta, event.wi.z());
float Fo = Fresnel::dielectricReflectance(eta, event.wo.z());
Vec3f diffuseAlbedo = albedo(event.info);
diffuseR = ((1.0f - Fi)*(1.0f - Fo)*eta*eta*event.wo.z()*INV_PI)*(diffuseAlbedo/(1.0f - diffuseAlbedo*_diffuseFresnel));
if (_scaledSigmaA.max() > 0.0f)
diffuseR *= std::exp(_scaledSigmaA*(-1.0f/event.wo.z() - 1.0f/event.wi.z()));
}
return glossyR + diffuseR;
}
Vec3f RoughCoatBsdf::eval(const SurfaceScatterEvent &event) const
{
bool sampleR = event.requestedLobe.test(BsdfLobes::GlossyReflectionLobe);
bool sampleT = event.requestedLobe.test(_substrate->lobes());
if (!sampleT && !sampleR)
return Vec3f(0.0f);
if (event.wi.z() <= 0.0f || event.wo.z() <= 0.0f)
return Vec3f(0.0f);
Vec3f glossyR(0.0f);
if (sampleR)
glossyR = RoughDielectricBsdf::evalBase(event, true, false, (*_roughness)[*event.info].x(), _ior, _distribution);
Vec3f substrateR(0.0f);
if (sampleT) {
const Vec3f &wi = event.wi;
const Vec3f &wo = event.wo;
float eta = 1.0f/_ior;
float cosThetaTi, cosThetaTo;
float Fi = Fresnel::dielectricReflectance(eta, wi.z(), cosThetaTi);
float Fo = Fresnel::dielectricReflectance(eta, wo.z(), cosThetaTo);
if (Fi == 1.0f || Fo == 1.0f)
return glossyR;
Vec3f wiSubstrate(wi.x()*eta, wi.y()*eta, std::copysign(cosThetaTi, wi.z()));
Vec3f woSubstrate(wo.x()*eta, wo.y()*eta, std::copysign(cosThetaTo, wo.z()));
float compressionProjection = eta*eta*wo.z()/cosThetaTo;
Vec3f substrateF = _substrate->eval(event.makeWarpedQuery(wiSubstrate, woSubstrate));
if (_scaledSigmaA.max() > 0.0f)
substrateF *= std::exp(_scaledSigmaA*(-1.0f/cosThetaTo - 1.0f/cosThetaTi));
substrateR = compressionProjection*(1.0f - Fi)*(1.0f - Fo)*substrateF;
}
return glossyR + substrateR;
}