static Vector hemisphereSample(const Vector& normal)
{
Random& rnd = getRandomGen();
double u = rnd.randdouble();
double v = rnd.randdouble();
double theta = 2 * PI * u;
double phi = acos(2 * v - 1);
Vector vec(
cos(theta) * sin(phi),
cos(phi),
sin(theta) * sin(phi)
);
if (dot(vec, normal) < 0)
vec = -vec;
return vec;
}
Color Refl::shade(const Ray& ray, const IntersectionInfo& info)
{
Vector n = faceforward(ray.dir, info.normal);
if (glossiness == 1) {
Ray newRay = ray;
newRay.start = info.ip + n * 0.000001;
newRay.dir = reflect(ray.dir, n);
newRay.depth++;
return raytrace(newRay) * multiplier;
} else {
Random& rnd = getRandomGen();
Color result(0, 0, 0);
int count = numSamples;
if (ray.depth > 0)
count = 2;
for (int i = 0; i < count; i++) {
Vector a, b;
orthonormalSystem(n, a, b);
double x, y, scaling;
rnd.unitDiscSample(x, y);
//
scaling = tan((1 - glossiness) * PI/2);
x *= scaling;
y *= scaling;
Vector modifiedNormal = n + a * x + b * y;
Ray newRay = ray;
newRay.start = info.ip + n * 0.000001;
newRay.dir = reflect(ray.dir, modifiedNormal);
newRay.depth++;
result += raytrace(newRay) * multiplier;
}
return result / count;
}
}
void RectLight::getNthSample(int sampleIdx, const Vector& hitPos, Vector& samplePos, Color& color)
{
Random& rnd = getRandomGen();
// stratified sampling: subdivide the unit square into xSubd * ySubd subrectangles
// and take a random points from each one of them. I.e., getNthSample() gets a random sample
// from one of those subrectangles. The subrectangle in question is determined by sampleIdx.
float x = (sampleIdx % xSubd + rnd.randfloat()) / (float) xSubd;
float y = (sampleIdx / xSubd + rnd.randfloat()) / (float) ySubd;
// create the sample in local space - in the (-0.5, 0, -0.5) -- (0.5, 0, 0.5) square
Vector sample(x - 0.5, 0, y - 0.5);
samplePos = T.transformPoint(sample); // transform the sample into world space
// transform the point that is to be shaded into local space first
Vector hitPos_LS = IT.transformPoint(hitPos);
if (hitPos_LS.y > 0) {
color.makeZero(); // point is behind the light - unilluminated.
} else {
// otherwise, return light color, attenuated by the angle of incidence
// (the cosine between the light's direction and the normed ray toward the hitpos)
color = this->col * float((area * dot(Vector(0, -1, 0), hitPos_LS) / hitPos_LS.length()));
}
}
Random& getRandomGen()
{
return getRandomGen(SDL_ThreadID());
}
