public Color PathTrace(Ray ray, HitRecord record, List <List <Sample> > subPathSamples, LightSample lightSample)
{
float q = 0f;
int depth = 0;
Color pixelColor = new Color(0, 0, 0);
Color alpha = new Color(1, 1, 1);
bool isGeneratedFromRefraction = false;
while (depth < Constants.MaximalPathLength)
{
if (record == null)
{
return(pixelColor);
}
//Select one light at random
ILight light = Randomizer.PickRandomLight(lights);
//Sample that light
light.Sample(record, lightSample);
if (isGeneratedFromRefraction && record.HitObject.Light != null)
{
isGeneratedFromRefraction = false;
pixelColor.Append(record.HitObject.Light.LightColor);
}
pixelColor.Append(alpha.Mult(Shade(record, lightSample)).Div(lightSample.Pdf));
//Break with Russian roulette
if (depth > 2)
{
q = 0.5f;
if (random.NextDouble() <= q)
{
return(pixelColor);
}
}
List <Sample> directionSamples = subPathSamples[depth];
//Create the next Ray
if (record.Material is LambertMaterial || record.Material is BlinnPhongMaterial)
{
Sample directionSample = Randomizer.PickRandomSample(directionSamples);
Vector3 direction = UniformHemisphereSample(directionSample.X, directionSample.Y, record.SurfaceNormal);
record = scene.Intersect(new Ray(record.IntersectionPoint, direction));
if (record == null)
{
break;
}
alpha = alpha.Mult(record.Material.Diffuse.Div(1 - q));
}
else if (record.Material is MirrorMaterial)
{
record = scene.Intersect(record.CreateReflectedRay());
isGeneratedFromRefraction = true;
}
else if (record.Material is RefractiveMaterial)
{
isGeneratedFromRefraction = true;
float fresnel = Reflectance(record);
//Pick refraction / reflection path with p=0.5 each
if (random.NextDouble() < fresnel)
{
record = scene.Intersect(record.CreateReflectedRay());
alpha = alpha.Mult(fresnel);
}
else
{
record = scene.Intersect(record.CreateRefractedRay());
alpha = alpha.Mult(1 - fresnel);
}
}
depth++;
}
return(pixelColor);
}
