/// <summary>
/// Sample returns a single possible direction
/// </summary>
/// <param name="woL"></param>
/// <returns></returns>
public override (Spectrum, Vector3, double) Sample_f(Vector3 wo)
{
var F = fresnel.Evaluate(Utils.CosTheta(wo));
bool entering = Utils.CosTheta(wo) > 0;
var etaI = entering ? fresnel.EtaI : fresnel.EtaT;
var etaT = entering ? fresnel.EtaT : fresnel.EtaI;
var n = new Vector3(0, 0, 1);
n = Vector3.Dot(n, wo) < 0 ? -n : n;
var(refracted, wt) = Refract(wo, n, etaI / etaT);
if (!refracted)
{
return(Spectrum.ZeroSpectrum, null, 0);
}
Spectrum ft = r * (1 - F.Max());
var pdf = 1 - F.Max();
return(ft / Utils.AbsCosTheta(wt), wt, pdf);
}
/// <summary>
/// Sample returns a single possible direction
/// </summary>
/// <param name="woL"></param>
/// <returns></returns>
public override (Spectrum, Vector3, double) Sample_f(Vector3 woL)
{
// perfect specular reflection
Vector3 wiL = new Vector3(-woL.x, -woL.y, woL.z);
Spectrum ft = r * fresnel.Evaluate(Utils.CosTheta(wiL));
return(ft / Utils.AbsCosTheta(wiL), wiL, 1);
}
