public Spectrum Li(Ray r, Scene s)
{
/* BASIC Implement
repeat
r <- random ray from camera
L <- 0, β <- 1, nbounces <- 0
repeat
isect <- intersect r with scene
if isect == null // no hit
break
wo <- -r
if isect == light // light hit
L<- β*Le(wo) // add light emitted
break
wi <- random ray from isect
(f,pr) <- bsdf(isect,wi,wo)
β <- β*f*|cosθ|/pr
r <- wi
nbounces <- nbounces+1
AddSampleToImage(L,r)
*/
/* Russian Roulette Implement
(f,pr) <- bsdf(isect,wi,wo)
β <- β*f*|cosθ|/pr
r <- wi
if nbounces>3
q <- 1 - max(β)
if random() < q
break
β <- β/(1-q)
*/
var L = Spectrum.ZeroSpectrum;
var beta = Spectrum.Create((double)1);
int nbounces = 0;
double q;
while(nbounces < 20) {
(double? mint, SurfaceInteraction si) = s.Intersect(r);
// If nothing hit end
if (si == null) {
break;
}
// If Light hit include it and finish
if (si.Obj is Light) {
if (nbounces == 0)
{
L = beta * si.Le(si.Wo);
//Console.WriteLine(beta.c);
//Console.WriteLine(L.c);
}
break;
}
// Sample light from SurfaceInteraction
// TODO
Spectrum Ld = Light.UniformSampleOneLight(si, s);
L = L.AddTo(beta * Ld);
// Make new reflected Ray
//Ray wi = si.SpawnRay(UniformSampleSphere());
// Get BSDF of hit object
(Spectrum f, Vector3 wi, double pr, bool p) = (si.Obj as Shape).BSDF.Sample_f(si.Wo, si);
// Update beta
beta = beta * f * Utils.AbsCosTheta(wi) / pr;
// Set reflected Ray as original Ray
r = new Ray(si.Point, wi);
if (nbounces > 3) {
q = 1 - beta.Max();
if (ThreadSafeRandom.NextDouble() < q) {
break;
}
beta /= (1 - q);
}
nbounces += 1;
}
Console.WriteLine(L.c);
return L;
}