NearestIntersection findNearestIntersection(const Scene& scene, const Ray& ray)
{
NearestIntersection result;
for (Scene::ConstIterator it = scene.Begin(); it != scene.End(); it++)
{
const RayIntersectionPoint& bestIntersection = result.intersection;
RayIntersectionPoint intersection = (*it)->getIntersection(ray);
if (!intersection.isNull())
{
if ((result.isNull()) || intersection.getDistance() < bestIntersection.getDistance())
{
result.intersection = intersection;
result.primitive = (*it);
}
}
}
return result;
}
Color trace(const Scene& scene, Ray ray, int depth)
{
const Color background(0,0,0);
const int maxDepth = 3;
if (depth >= maxDepth)
return background;
Color color(0,0,0);
double distance = 0;
const Primitive* prim = NULL;
int intersectionType = 0;
findNearsetIntersection(scene, ray, &prim, &distance, &intersectionType);
if (prim != NULL)
{
if (prim->IsIlluminative())
{
return prim->GetMaterial().GetColor();
}
const Vector3 intersectionPoint = ray.GetPoint(distance);
const Vector3 n = prim->GetNormal(intersectionPoint);
if (prim->GetMaterial().GetDiffuse() > 0)
{
for (Scene::ConstIterator it = scene.Begin(); it != scene.End(); it++)
{
const double intensive = getIntensity((*it), intersectionPoint, n, scene);
if (intensive != .0)
{
Vector3 x = (prim->GetMaterial().GetColor());
Vector3 y = ((*it)->GetMaterial().GetColor());
color = color + (intensive * prim->GetMaterial().GetDiffuse()) * x * y;
}
}
}
//refraction
{
const Vector3 x = ray.GetDirection();
const Vector3 y = intersectionType * (-n);
double n;
if (intersectionType == IntersectOutside)
n = 1.0 / prim->GetMaterial().GetRefractionRate();
else
n = prim->GetMaterial().GetRefractionRate();
const double sin_1 = sqrt(1 - Dot(x,y));
const double sin_2 = n * sin_1;
if (sin_2 < 1)
{
const double cos_2 = sqrt(1 - sin_2);
Vector3 xPerpendicular = x - Dot(x,y)*y;
Vector3 z = cos_2 * y + sin_2 * xPerpendicular;
z.Normalize();
if (prim->GetMaterial().GetRefraction() > 0)
{
if (intersectionType == IntersectInside)
{
color = color +
prim->GetMaterial().GetRefraction() *
exp(-prim->GetMaterial().GetAbsorptionRate()*distance) *
trace(scene, Ray(intersectionPoint, z), depth + 1);
}
else
color = color +
prim->GetMaterial().GetRefraction() * trace(scene, Ray(intersectionPoint, z), depth + 1);
}
}
}
//reflection
if (prim->GetMaterial().GetReflection() > 0)
{
const Vector3 a = ray.GetDirection();
Vector3 newA = a - 2 * (Dot(a,n)) * n;
color = color + prim->GetMaterial().GetReflection() * trace(scene, Ray(intersectionPoint, newA), depth + 1);
}
}
return color;
}