public static Vector Radiance(Ray ray)
{
const int MAX_BOUNCES = 10;
Vector weights = new Vector(1.0f, 1.0f, 1.0f);
Vector radiance = Vector.Zero;
for (int bounce = 0; bounce < MAX_BOUNCES; ++bounce)
{
float distance;
int hitSphere;
if (!Intersect(ray, out hitSphere, out distance))
{
break;
}
Sphere sphere = geometry[hitSphere];
IMaterial material = materials[hitSphere];
var hitPoint = Ray.PointAt(ray, distance);
var basis = new Basis(sphere.Normal(hitPoint));
var outgoing = new Direction(-ray.Direction, basis);
/* Include object emittance as light path */
radiance += weights * material.Emittance(outgoing, basis);
/* Include point light source light paths */
foreach (var light in lights)
{
var pointToLight = light.position - hitPoint;
var lightDistance = pointToLight.Length();
if (!Occlude(new Ray(hitPoint, pointToLight), 1e-4f, lightDistance))
{
Direction incomimg = new Direction(pointToLight / lightDistance, basis);
radiance += weights * material.BRDF(incomimg, outgoing, basis) * incomimg.CosTheta
* light.intensity / (lightDistance * lightDistance);
}
}
/* Russian roulette */
Vector weight = material.WeightPDF(outgoing, basis);
float p = Math.Max(weight.X, Math.Max(weight.Y, weight.Z));
if (bounce > 2)
{
if (random.NextDouble() <= p)
{
weight /= p;
}
else
{
break;
}
}
/* Update light path weights and prepare for next bounce */
weights *= weight;
var newDir = material.SamplePDF(outgoing, basis, random);
ray = new Ray(hitPoint, newDir);
}
return(radiance);
}