// sample: samples a single path up to a maximum depth
private Vector3 Sample(Ray ray, int depth, int x, int y)
{
// find nearest ray/scene intersection
Scene.Intersect(ray);
if (ray.objIdx == -1)
{
// no scene primitive encountered; skybox
return(1.0f * scene.SampleSkydome(ray.D));
}
// calculate intersection point
Vector3 I = ray.O + ray.t * ray.D;
// get material at intersection point
Material material = scene.GetMaterial(ray.objIdx, I);
if (material.emissive)
{
// hit light
return(material.diffuse);
}
// terminate if path is too long
if (depth >= MAXDEPTH)
{
return(Vector3.Zero);
}
// handle material interaction
float r0 = RTTools.RandomFloat();
Vector3 R = Vector3.Zero;
if (r0 < material.refr)
{
// dielectric: refract or reflect
RTTools.Refraction(ray.inside, ray.D, ray.N, ref R);
Ray extensionRay = new Ray(I + R * EPSILON, R, 1e34f);
extensionRay.inside = (Vector3.Dot(ray.N, R) < 0);
return(material.diffuse * Sample(extensionRay, depth + 1, x, y));
}
else if ((r0 < (material.refl + material.refr)) && (depth < MAXDEPTH))
{
// pure specular reflection
R = Vector3.Reflect(ray.D, ray.N);
Ray extensionRay = new Ray(I + R * EPSILON, R, 1e34f);
return(material.diffuse * Sample(extensionRay, depth + 1, x, y));
}
else
{
// diffuse reflection
if (x == 500 && y == 400)
{
//Console.WriteLine("test");
//return new Vector3(255,255,255);
}
R = RTTools.DiffuseReflection(RTTools.GetRNG(), ray.N);
Ray extensionRay = new Ray(I + R * EPSILON, R, 1e34f);
return(Vector3.Dot(R, ray.N) * material.diffuse * Sample(extensionRay, depth + 1, x, y));
}
}
static public void Refraction(bool inside, Vector3 D, Vector3 N, ref Vector3 R)
{
float nc = inside ? 1 : 1.2f, nt = inside ? 1.2f : 1;
float nnt = nt / nc, ddn = Vector3.Dot(D, N);
float cos2t = 1.0f - nnt * nnt * (1 - ddn * ddn);
R = Vector3.Reflect(D, N);
if (cos2t >= 0)
{
float r1 = RTTools.RandomFloat();
float a = nt - nc, b = nt + nc, R0 = a * a / (b * b), c = 1 + ddn;
float Tr = 1 - (R0 + (1 - R0) * c * c * c * c * c);
if (r1 < Tr)
{
R = (D * nnt - N * (ddn * nnt + (float)Math.Sqrt(cos2t)));
}
}
}
