std::vector<PathNode> BidirectionalIntegrator::generateEyePath(Ray r)
{
std::vector<PathNode> eyePath;
eyePath.clear();
Intersection isx = intersection_engine->GetIntersection(r);
int depth=0;
while(depth<max_depth && isx.t > 0)
{
// store the path node
PathNode node;
node.isx = isx;
node.dirIn_world = -r.direction;
node.dirIn_local = isx.ToLocalNormalCoordinate(-r.direction);
node.F = isx.object_hit->material->SampleAndEvaluateScatteredEnergy(isx,node.dirIn_local,node.dirOut_local,node.pdf);
node.dirOut_world = isx.ToWorldNormalCoordinate(node.dirOut_local);
if(node.pdf != 0)
eyePath.push_back(node);
else
break;
//update r
r = Ray(isx.point + glm::sign(glm::dot(node.dirOut_world,isx.normal)) * isx.normal*1e-3f, node.dirOut_world);
// update isx and depth info
depth++;
isx = intersection_engine->GetIntersection(r);
}
return eyePath;
}
// MIS: sampling BRDF
glm::vec3 BidirectionalIntegrator::MIS_SampleBRDF(Intersection &intersection, Ray &r, Geometry* &light)
{
if(Number_BRDF == 0)
return glm::vec3(0);
// Direct light estimator: sample BRDF
glm::vec3 sum_brdf_sample(0.0f);
for(int i = 0; i < Number_BRDF; i++)
{
glm::vec3 wo_local = intersection.ToLocalNormalCoordinate(-r.direction);
glm::vec3 wj_local;
float pdf_brdf;
glm::vec3 F = intersection.object_hit->material->SampleAndEvaluateScatteredEnergy(intersection,wo_local,wj_local,pdf_brdf);
glm::vec3 wj_world = intersection.ToWorldNormalCoordinate(wj_local);
glm::vec3 wo_world = - r.direction;
Intersection isxOnLight = intersection_engine->GetIntersection(Ray(intersection.point+float(1e-3)*intersection.normal, wj_world));
if(isxOnLight.t > 0 && isxOnLight.object_hit == light && pdf_brdf > 0)
{
float temp,pdf_light = light->RayPDF(intersection, Ray(intersection.point, wj_world));
float W = PowerHeuristic(pdf_brdf,float(Number_BRDF),pdf_light,float(Number_Light));
glm::vec3 Ld = light->material->EvaluateScatteredEnergy(isxOnLight,wo_world,-wj_world,temp);
if(pdf_light > 0 )
{
if(isinf(pdf_brdf)) // delta specular surface
{
sum_brdf_sample = sum_brdf_sample +
F * Ld * float(fabs(glm::dot(wj_world, intersection.normal))) / pdf_light;
}
else
{
sum_brdf_sample = sum_brdf_sample +
W * F * Ld * float(fabs(glm::dot(wj_world,intersection.normal))) / pdf_brdf;
}
}
}
}
return sum_brdf_sample / float(Number_BRDF);
}
std::vector<PathNode> BidirectionalIntegrator::generateLightPath(Geometry* &light)
{
std::vector<PathNode> lightPath;
lightPath.clear();
Intersection lightSample = light->RandomSampleOnSurface(uniform_distribution(generator),uniform_distribution(generator));
Ray r(lightSample.point, lightSample.point - light->transform.position());
Intersection isx = intersection_engine->GetIntersection(r);
int depth = 0;
while(isx.t > 0 && depth < max_depth)
{
// store pathnode on the light path
PathNode node;
node.isx = isx;
node.dirIn_world = -r.direction;
node.dirIn_local = isx.ToLocalNormalCoordinate(-r.direction);
node.F = isx.object_hit->material->SampleAndEvaluateScatteredEnergy(isx,node.dirIn_local,node.dirOut_local,node.pdf);
node.dirOut_world = isx.ToWorldNormalCoordinate(node.dirOut_local);
if(node.pdf != 0)
lightPath.push_back(node);
else
break;
//update r
r = Ray(isx.point + glm::sign(glm::dot(node.dirOut_world,isx.normal)) * isx.normal*1e-3f, node.dirOut_world);
// update isx and depth info
depth++;
isx = intersection_engine->GetIntersection(r);
}
return lightPath;
}
