// BxDF Method Definitions
bool BxDF::SampleF(const SpectrumWavelengths &sw, const Vector &wo, Vector *wi,
float u1, float u2, SWCSpectrum *const f, float *pdf, float *pdfBack,
bool reverse) const
{
// Cosine-sample the hemisphere, flipping the direction if necessary
*wi = CosineSampleHemisphere(u1, u2);
if (wo.z < 0.f)
wi->z = -(wi->z);
// wi may be in the tangent plane, which will
// fail the SameHemisphere test in Pdf()
if (!SameHemisphere(wo, *wi))
return false;
*pdf = Pdf(sw, wo, *wi);
if (pdfBack)
*pdfBack = Pdf(sw, *wi, wo);
*f = SWCSpectrum(0.f);
if (reverse)
F(sw, *wi, wo, f);
else
F(sw, wo, *wi, f);
*f /= *pdf;
return true;
}
SWCSpectrum FresnelApproxEta(const SWCSpectrum &Fr) {
SWCSpectrum sqrtReflectance = Sqrt(Fr.Clamp(0.f, .999f));
return (SWCSpectrum(1.f) + sqrtReflectance) /
(SWCSpectrum(1.f) - sqrtReflectance);
}
SWCSpectrum FresnelApproxK(const SWCSpectrum &Fr) {
SWCSpectrum reflectance = Fr.Clamp(0.f, .999f);
return 2.f * Sqrt(reflectance /
(SWCSpectrum(1.f) - reflectance));
}
// Utility Functions
void FrDiel(float cosi, float cost,
const SWCSpectrum &etai, const SWCSpectrum &etat, SWCSpectrum *const f)
{
FrDiel2(cosi, SWCSpectrum(cost), etat / etai, f);
}
