Spectrum FresnelBlend::f(const Vector &wo,
const Vector &wi) const {
Spectrum diffuse = (28.f/(23.f*M_PI)) * Rd *
(Spectrum(1.) - Rs) *
(1 - powf(1 - .5f * fabsf(CosTheta(wi)), 5)) *
(1 - powf(1 - .5f * fabsf(CosTheta(wo)), 5));
Vector H = Normalize(wi + wo);
Spectrum specular = distribution->D(H) /
(8.f * M_PI * AbsDot(wi, H) *
max(fabsf(CosTheta(wi)), fabsf(CosTheta(wo)))) *
SchlickFresnel(Dot(wi, H));
return diffuse + specular;
}
Spectrum FresnelBlend::f(const Vector3f &wo, const Vector3f &wi) const {
auto pow5 = [](Float v) { return (v * v) * (v * v) * v; };
Spectrum diffuse = (28.f / (23.f * Pi)) * Rd * (Spectrum(1.f) - Rs) *
(1 - pow5(1 - .5f * AbsCosTheta(wi))) *
(1 - pow5(1 - .5f * AbsCosTheta(wo)));
Vector3f wh = wi + wo;
if (wh.x == 0 && wh.y == 0 && wh.z == 0) return Spectrum(0);
wh = Normalize(wh);
Spectrum specular =
distribution->D(wh) /
(4 * AbsDot(wi, wh) * std::max(AbsCosTheta(wi), AbsCosTheta(wo))) *
SchlickFresnel(Dot(wi, wh));
return diffuse + specular;
}
