// 鏡面反射
Color PathTracer::Radiance_Specular(const Scene &scene, const Ray &ray, Random &rnd, const int depth, Scene::IntersectionInformation &intersect, const Vector3 &normal, double russian_roulette_prob) {
Vector3 reflected_dir(ray.dir - normal*2*ray.dir.dot(normal));
reflected_dir.normalize();
// 間接光の評価
Ray newray(intersect.hit.position, reflected_dir);
Color income = Radiance(scene, newray, rnd, depth+1);
// 直接光の評価
Scene::IntersectionInformation newhit;
if (m_performNextEventEstimation && scene.CheckIntersection(newray, newhit)) {
income += newhit.object->material.emission;
}
Color weight = intersect.texturedHitpointColor / russian_roulette_prob;
return Vector3(weight.x*income.x, weight.y*income.y, weight.z*income.z);
}
Color PathTracer::Radiance(const Scene &scene, const Ray &ray, Random &rnd, const int depth) {
Scene::IntersectionInformation intersect;
m_checkIntersectionCount++;
bool intersected = scene.CheckIntersection(ray, intersect);
Vector3 normal;
if (intersected) {
normal = intersect.hit.normal.dot(ray.dir) < 0.0 ? intersect.hit.normal : intersect.hit.normal * -1.0;
}
Color income;// = DirectRadiance(scene, ray, rnd, depth, intersected, intersect, normal);
income += Radiance_internal(scene, ray, rnd, depth, intersected, intersect, normal);
return income;
}
// 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);
}
// 直接光による Radiance の評価
Color PathTracer::DirectRadiance_Lambert(const Scene &scene, const Ray &ray, Random &rnd, const int depth, const bool intersected, Scene::IntersectionInformation &intersect, const Vector3 &normal) {
assert(intersected);
// ライトに当たっていたら無視
if (dynamic_cast<LightBase *>(intersect.object) != nullptr)
{
return Color(0, 0, 0);
}
const vector<LightBase *> &lights = scene.GetLights();
if (lights.size() == 0) return scene.Background();
// pick a random light according to light power
double totalPower = 0.0;
vector<double> eachLightProbability, accumulatedProbability;
for (size_t i = 0; i < lights.size(); i++) {
double power = lights[i]->TotalPower();
eachLightProbability.push_back(power);
accumulatedProbability.push_back(totalPower + power);
totalPower += power;
}
// 確率へ正規化
for (size_t i = 0; i < lights.size(); i++) {
eachLightProbability[i] /= totalPower;
accumulatedProbability[i] /= totalPower;
}
static const int NumberOfLightSamples = 1;
Color income;
for (int lightCount = 0; lightCount < NumberOfLightSamples; lightCount++) {
double next = rnd.nextDouble();
int index = 0;
for (size_t i = 0; i < lights.size(); i++) {
if (next <= accumulatedProbability[i]) {
index = i; break;
}
}
const LightBase *selectedLight = lights[index];
// pick a one point
Vector3 point, light_normal; double pdf = 0.0;
//selectedLight->SampleOnePoint(point, light_normal, pdf, rnd);
if (!selectedLight->SampleOnePointWithTargetPoint(point, light_normal, pdf, intersect.hit.position, rnd)) {
continue;
}
Vector3 dir((point - intersect.hit.position)); dir.normalize();
double cos_shita = dir.dot(normal);
double light_cos_shita = -dir.dot(light_normal);
if (cos_shita < 0 || light_cos_shita < 0) {
// cannot reach to the light
continue;
}
// check visibility
Scene::IntersectionInformation hit;
if (scene.CheckIntersection(Ray(intersect.hit.position, dir), hit)) {
if (dynamic_cast<LightBase *>(hit.object) == selectedLight) {
// visible
// BRDF = color/PI
double G = cos_shita * light_cos_shita / (hit.hit.distance * hit.hit.distance);
Vector3 reflect_rate(intersect.texturedHitpointColor / PI * G / (pdf * eachLightProbability[index]));
income.x += reflect_rate.x * hit.object->material.emission.x;
income.y += reflect_rate.y * hit.object->material.emission.y;
income.z += reflect_rate.z * hit.object->material.emission.z;
// direct_illum = 1/N*ΣL_e*BRDF*G*V/pdf(light)
m_hitToLightCount++;
}
}
m_omittedRayCount++;
}
return income / NumberOfLightSamples;
}