Color ray_shade(int level, Real w, Ray v, RContext *rc, Object *ol)
{
Inode *i = ray_intersect(ol, v);
if (i != NULL) { Light *l; Real wf;
Material *m = i->m;
Vector3 p = ray_point(v, i->t);
Cone recv = cone_make(p, i->n, PIOVER2);
Color c = c_mult(m->c, c_scale(m->ka, ambient(rc)));
rc->p = p;
for (l = rc->l; l != NULL; l = l->next)
if ((*l->transport)(l, recv, rc) && (wf = shadow(l, p, ol)) > RAY_WF_MIN)
c = c_add(c, c_mult(m->c,
c_scale(wf * m->kd * v3_dot(l->outdir,i->n), l->outcol)));
if (level++ < MAX_RAY_LEVEL) {
if ((wf = w * m->ks) > RAY_WF_MIN) {
Ray r = ray_make(p, reflect_dir(v.d, i->n));
c = c_add(c, c_mult(m->s,
c_scale(m->ks, ray_shade(level, wf, r, rc, ol))));
}
if ((wf = w * m->kt) > RAY_WF_MIN) {
Ray t = ray_make(p, refract_dir(v.d, i->n, (i->enter)? 1/m->ir: m->ir));
if (v3_sqrnorm(t.d) > 0) {
c = c_add(c, c_mult(m->s,
c_scale(m->kt, ray_shade(level, wf, t, rc, ol))));
}
}
}
inode_free(i);
return c;
} else {
return BG_COLOR;
}
}
// 屈折面
Color PathTracer::Radiance_Refraction(const Scene &scene, const Ray &ray, Random &rnd, const int depth, Scene::IntersectionInformation &intersect, const Vector3 &normal, double russian_roulette_prob) {
bool into = intersect.hit.normal.dot(normal) > 0.0;
Vector3 reflect_dir = ray.dir - normal*2*ray.dir.dot(normal);
reflect_dir.normalize();
double n_vacuum = REFRACTIVE_INDEX_VACUUM;
double n_obj = intersect.object->material.refraction_rate;
double n_ratio = into ? n_vacuum/n_obj : n_obj/n_vacuum;
double dot = ray.dir.dot(normal);
double cos2t = 1-n_ratio*n_ratio*(1-dot*dot);
// 反射方向の直接光の評価
Color reflect_direct;
Ray reflect_ray(intersect.hit.position, reflect_dir);
Scene::IntersectionInformation reflected_hit;
if (m_performNextEventEstimation && scene.CheckIntersection(reflect_ray, reflected_hit)) {
reflect_direct = reflected_hit.object->material.emission;
}
if (cos2t < 0) {
// 全反射
Color income = reflect_direct + Radiance(scene, Ray(intersect.hit.position, reflect_dir), rnd, depth+1);
Color weight = intersect.object->material.color / russian_roulette_prob;
return Vector3(weight.x*income.x, weight.y*income.y, weight.z*income.z);
}
// 屈折方向
Vector3 refract_dir( ray.dir*n_ratio - intersect.hit.normal * (into ? 1.0 : -1.0) * (dot*n_ratio + sqrt(cos2t)) );
refract_dir.normalize();
const Ray refract_ray(intersect.hit.position, refract_dir);
// 屈折方向の直接光の評価
Color refract_direct;
if (m_performNextEventEstimation && scene.CheckIntersection(refract_ray, reflected_hit)) {
refract_direct = reflected_hit.object->material.emission;
}
// Fresnel の式
double F0 = (n_obj-n_vacuum)*(n_obj-n_vacuum)/((n_obj+n_vacuum)*(n_obj+n_vacuum));
double c = 1 - ( into ? -dot : -refract_dir.dot(normal) ); // 1-cosθ
double Fr = F0 + (1-F0)*pow(c, 5.0); // Fresnel (反射の割合)
double n_ratio2 = n_ratio*n_ratio; // 屈折前後での放射輝度の変化率
double Tr = (1-Fr)*n_ratio2; // 屈折直後→直前の割合
Color income, weight;
if (depth > 2) {
// 反射 or 屈折のみ追跡
const double reflect_prob = 0.1 + 0.8 * Fr;
if (rnd.nextDouble() < reflect_prob) {
// 反射
income = (reflect_direct + Radiance(scene, Ray(intersect.hit.position, reflect_dir), rnd, depth+1)) * Fr;
weight = intersect.texturedHitpointColor / (russian_roulette_prob * reflect_prob);
} else {
// 屈折
income = (refract_direct + Radiance(scene, refract_ray, rnd, depth+1)) * Tr;
weight = intersect.texturedHitpointColor / (russian_roulette_prob * (1 - reflect_prob));
}
} else {
// 反射と屈折両方追跡
m_omittedRayCount++;
income =
(reflect_direct + Radiance(scene, Ray(intersect.hit.position, reflect_dir), rnd, depth+1)) * Fr +
(refract_direct + Radiance(scene, refract_ray, rnd, depth + 1)) *Tr;
weight = intersect.texturedHitpointColor / russian_roulette_prob;
}
return /*intersect.object->material.emission +*/ Vector3(weight.x*income.x, weight.y*income.y, weight.z*income.z);
}
