public virtual Spectrum rho(int nSamples, IEnumerable <Point2D> samples1, IEnumerable <Point2D> samples2)
{
var u1 = samples1.ToList();
var u2 = samples2.ToList();
Spectrum r = Spectrum.Create(0.0);
for (int i = 0; i < nSamples; ++i)
{
// Estimate one term of $\rho_\roman{hh}$
Vector3D wo = Sampling.UniformSampleHemisphere(u1[i]);
double pdfo = Sampling.UniformHemispherePdf();
Spectrum f = Sample_f(wo, out Vector3D wi, u2[i], out double pdfi, out BxdfType sampledType);
if (pdfi > 0)
{
r += f * Reflection.AbsCosTheta(wi) * Reflection.AbsCosTheta(wo) / (pdfo * pdfi);
}
}
return(r / (Math.PI * nSamples));
}
public virtual Spectrum Sample_f(
Vector3D wo,
out Vector3D wi,
Point2D sample,
out double pdf,
out BxdfType sampledType)
{
sampledType = BxdfType.None;
// Cosine-sample the hemisphere, flipping the direction if necessary
wi = Sampling.CosineSampleHemisphere(sample);
if (wo.Z < 0.0)
{
wi = new Vector3D(wi.X, wi.Y, -wi.Z);
}
pdf = Pdf(wo, wi);
return(f(wo, wi));
}