public Vec3f trace(Vec3f rayorig, Vec3f raydir, List <Sphere> spheres, int depth)
{
float tnear = INFINITY;
Sphere sphere = null;
//find intersection of this ray with the sphere in the scene
int spCount = spheres.Count();
for (int i = 0; i < spCount; ++i)
{
float t0 = INFINITY;
float t1 = INFINITY;
(bool, float, float)inter = spheres[i].intersect(rayorig, raydir);
if (inter.Item1)
{
t0 = inter.Item2;
t1 = inter.Item3;
if (t0 < 0)
{
t0 = t1;
}
if (t0 < tnear)
{
tnear = t0;
sphere = spheres[i];
}
}
}
//if there's no intersection return black or background color
if (sphere == null)
{
return(new Vec3f(1.0f));
}
Vec3f surfaceColor = new Vec3f(0.0f); //color of the ray/surfaceof the object intersected by the ray
Vec3f phit = rayorig + raydir * tnear; //point of intersection
Vec3f nhit = phit - sphere.center; //normal at the intersection point
nhit.normalize(); //normalize normal direction
//If the normal and the view direction are not opposite to each other
//reverse the normal direction. That also means we are inside the sphere so set
//the inside bool to true. Finally reverse the sign of IdotN which we want
//positive.
float bias = 0.0001f; //add some bias to the point from which we will be tracing
bool inside = false;
if (raydir.dot(nhit) > 0)
{
nhit = -1 * nhit;
inside = true;
}
if ((sphere.transparency > 0 || sphere.reflection > 0) && depth < MAX_RAY_DEPTH)
{
float facingratio = -raydir.dot(nhit);
// change the mix value to tweak the effect
float fresneleffect = mix((float)Math.Pow(1 - facingratio, 3), 1, 0.1f);
// compute reflection direction (not need to normalize because all vectors
// are already normalized)
Vec3f refldir = raydir.reflect(nhit);
refldir.normalize();
Vec3f reflection = trace(phit + nhit * bias, refldir, spheres, depth + 1);
Vec3f refraction = new Vec3f(0.0f);
// if the sphere is also transparent compute refraction ray (transmission)
if (sphere.transparency != 0.0f)
{
float ior = 1.1f;
float eta = (inside) ? ior : 1 / ior; // are we inside or outside the surface?
float cosi = -nhit.dot(raydir);
float k = 1 - eta * eta * (1 - cosi * cosi);
Vec3f refrdir = raydir * eta + nhit * (eta * cosi - (float)Math.Sqrt(k));
refrdir.normalize();
refraction = trace(phit - nhit * bias, refrdir, spheres, depth + 1);
}
// the result is a mix of reflection and refraction (if the sphere is transparent)
surfaceColor = (reflection * fresneleffect + refraction * (1.0f - fresneleffect) * sphere.transparency) * sphere.surfaceColor;
}
else
{
// it's a diffuse object, no need to raytrace any further
for (int i = 0; i < spCount; ++i)
{
if (spheres[i].emissionColor.x > 0)
{
// this is a light
Vec3f transmission = new Vec3f(1.0f);
Vec3f lightDirection = spheres[i].center - phit;
lightDirection.normalize();
for (int j = 0; j < spCount; ++j)
{
if (i != j)
{
if (spheres[j].intersect(phit + nhit * bias, lightDirection).Item1)
{
transmission = new Vec3f(0.0f);
break;
}
}
}
surfaceColor += sphere.surfaceColor * transmission * Math.Max(0.0f, nhit.dot(lightDirection)) * spheres[i].emissionColor;
}
}
}
return(surfaceColor + sphere.emissionColor);
}
