public override float Sample(Surfel surfel, out Vector3 wi, Vector2 sample, out float pdf)
{
var wo = surfel.ray;
var entering = Vector3.Dot(wo, surfel.normal) < 0;
var etaI = entering ? etaA : etaB;
var etaT = entering ? etaB : etaA;
var eta = etaI / etaT;
var n = Vector3Extensions.Faceforward(surfel.normal, wo);
if (!wo.Refract(n, eta, out wi))
{
pdf = 0;
return(0);
}
pdf = 1;
var cos = Vector3.Dot(wi, surfel.normal);
var ft = t * (1 - fresnel.Evaluate(cos));
if (mode == TransportMode.Radiance)
{
ft *= (etaI * etaI) / (etaT * etaT);
}
return(ft / Math.Abs(cos));
}
public override float Sample(Surfel surfel, out Vector3 wi, Vector2 sample, out float pdf)
{
float res;
var f = fresnel.Evaluate(Vector3.Dot(surfel.normal, surfel.ray));
if (sample.X < f)
{
res = reflection.Sample(surfel, out wi, sample, out pdf);
pdf = f;
}
else
{
res = transmission.Sample(surfel, out wi, sample, out pdf);
pdf = 1 - f;
}
return(res);
}