public virtual double Pdf(SurfaceInteraction si, Vector3 wi)
{
// Intersect sample ray with area light geometry
Ray ray = si.SpawnRay(wi);
(double?tHit, SurfaceInteraction isectLight) = Intersect(ray);
if (!tHit.HasValue)
{
return(0);
}
// Convert area measure to solid angle measure
double pdf = (si.Point - isectLight.Point).LengthSquared() / (Vector3.AbsDot(isectLight.Normal, -wi) * Area());
if (double.IsInfinity(pdf))
{
pdf = 0;
}
return(pdf);
}
public Spectrum Li(Ray r, Scene s)
{
Spectrum L = Spectrum.ZeroSpectrum;
Spectrum B = Spectrum.Create(1);
int nbounces = 0;
while (nbounces < 20)
{
SurfaceInteraction isect = null;
//Get the object the ray intersected with
isect = s.Intersect(r).Item2;
//If the ray hasn't hit anything return 0
if (isect == null)
{
break;
}
Vector3 wo = isect.Wo;//-r.d;
//If the ray hit a light, take its emission
if (isect.Obj is Light)
{
if (nbounces == 0)
{
L = B * isect.Le(wo);
}
break;
}
//Create a light ray from the intersection point and add its emission
Spectrum Ld = Light.UniformSampleOneLight(isect, s);
L = L.AddTo(B * Ld);
//Get the materials value at this point
(Spectrum f, Vector3 wi, double pr, bool specular) = (isect.Obj as Shape).BSDF.Sample_f(wo, isect);
if (!specular)
{
B = B * f * Utils.AbsCosTheta(wi) / pr;
}
//Spawn a new ray from the intersection
r = isect.SpawnRay(wi);
if (nbounces > 3)
{
double q = 1.0 - B.Max();
if (ThreadSafeRandom.NextDouble() < q)
{
break;
}
B = B / (1 - q);
}
nbounces++;
}
return(L);
}
