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#include "path_tracer.hpp"
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using namespace CGLA;
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path_tracer::path_tracer(int w, int h, bool explicit_direct, int subsamples)
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: tracer(w, h)
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{
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explicit_direct_ = explicit_direct;
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subsamples_ = subsamples;
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}
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CGLA::Vec3f path_tracer::trace(const ray& r, bool include_emitted)
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{
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//intersect ray with
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hit_info hi;
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bool hit = scene_->intersect(r, hi);
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if (!hit)
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return Vec3f(0.f);
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//Vec3f x, y, z = hi.shading_normal;
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//orthogonal(z, x, y);
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//return (Vec3f(hi.texcoords(0),hi.texcoords(1),0) + Vec3f(0.f)) / 1.f;
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//only include emitted light if requested
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CGLA::Vec3f Le(0.f);
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if (include_emitted)
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Le = hi.emitted;
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//compute reflectance for each bsdf component
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float rho_diffuse = intensity(hi.diffuse);
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float rho_glossy = intensity(hi.glossy);
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float rho_reflection = intensity(hi.reflection);
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float rho_refraction = intensity(hi.refraction);
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float rho_total = rho_diffuse+rho_glossy+rho_reflection+rho_refraction;
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assert(rho_total < 1.f);
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if (rho_total == 0.f)
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return Le;
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//compute direct lighting on hit point
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CGLA::Vec3f Ld(0.f);
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Vec3f wo = -r.direction;
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if (explicit_direct_ && rho_diffuse+rho_glossy>0.f)
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{
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size_t nlums = scene_->luminaires();
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for (size_t i=0; i<nlums; ++i)
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{
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const luminaire* lum = scene_->get_luminaire(i);
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int samples = lum->samples();
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Vec3f L(0.f);
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for (int j=0; j<samples; ++j)
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{
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Vec3f Li, wi;
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if (lum->sample(r, hi, Li, wi))
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{
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float cost = std::max(dot(hi.shading_normal, wi),0.f);
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L += Li * cost * bsdf_evaluate(hi, wi, wo);
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}
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Ld += L / float(samples);
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}
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}
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}
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//use russian roulette to terminate path
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float prussian = 1.f;
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float rr = random();
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if (r.depth > 3)
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{
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prussian = rho_total;
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if (rr >= prussian)
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return Ld + Le;
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}
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//figure out which bXdf to sample
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float pdiffuse = rho_diffuse/rho_total;
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float pglossy = rho_glossy/rho_total;
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float preflection = rho_reflection/rho_total;
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float prefraction = rho_refraction/rho_total;
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Vec3f wi;
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float pwi;
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Vec3f fs;
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bool sample_emitted = !explicit_direct_;
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if (rr <= pdiffuse)
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{
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//sample diffuse
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float pwi = sample_lambertian(hi, wo, wi);
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fs = lambertian_brdf(hi, wi, wo) / (pwi * pdiffuse * prussian);
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}
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else if (rr <= pdiffuse+pglossy)
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{
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//sample glossy part
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float pwi = sample_phong(hi, wo, wi);
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if (dot(hi.shading_normal, wi) <= 0.f)
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return Le + Ld;
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fs = phong_brdf(hi, wi, wo) / (pwi * pglossy * prussian);
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}
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else if (rr <= pdiffuse+pglossy+preflection)
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{
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//sample perfect specular reflection
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wi = reflect(hi.shading_normal, wo);
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pwi = 1.f;
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float cost = dot(hi.shading_normal, wo);
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fs = hi.reflection / (pwi * preflection * cost);
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sample_emitted = true;
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}
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else if (rr <= pdiffuse+pglossy+preflection+prefraction)
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{
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//sample perfect specular refraction
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bool not_tir = refract(hi.shading_normal, wo, 1.f/hi.ior, wi);
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assert(not_tir);
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pwi = 1.f;
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float cost = std::abs(dot(hi.shading_normal, wi));
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fs = hi.refraction / (pwi * prefraction * cost);
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sample_emitted = true;
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}
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else
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assert(false);
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//create aux ray
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ray s;
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s.origin = hi.position + epsilon * wi;
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s.direction = wi;
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s.depth = r.depth + 1;
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s.distance = std::numeric_limits<float>::infinity();
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float cost = std::abs(dot(hi.shading_normal, wi));
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Vec3f Li = cost * fs * trace(s, sample_emitted);
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//returm sum of emitted + direct + indirect
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return Le + Ld + Li;
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}
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Vec3f path_tracer::compute_pixel(int w, int h)
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{
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assert(scene_);
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//supersample
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Vec3f L(0.f);
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for (int j=0; j<subsamples_; ++j)
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{
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float y = h + (j + 0.5f) / subsamples_;
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for (int i=0; i<subsamples_; ++i)
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{
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float x = w + (i + 0.5f) / subsamples_;
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//ask camera for initial ray..
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Vec2f uv(x/width_, y/height_);
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ray r = scene_->get_camera()->generate(uv);
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//trace ray
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L += trace(r, true);
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}
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}
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return L / float(subsamples_ * subsamples_);
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}
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//02566 framework, Anders Wang Kristensen, awk@imm.dtu.dk, 2007
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