// generate samples void PathTracing::GenerateSample( const Sampler* sampler , PixelSample* samples , unsigned ps , const Scene& scene ) const { Integrator::GenerateSample( sampler , samples , ps , scene ); if( sampler->RoundSize( ps ) == ps ) { float* data_1d = samples[0].data; float* data_2d = samples[0].data + ps; sampler->Generate1D( data_1d , ps ); sampler->Generate2D( data_2d , ps ); for( unsigned k = 0 ; k < ps ; ++k ) { int two_k = 2*k; samples[k].bsdf_sample[0].t = data_1d[k]; samples[k].bsdf_sample[0].u = data_2d[two_k]; samples[k].bsdf_sample[0].v = data_2d[two_k+1]; } sampler->Generate1D( data_1d , ps ); sampler->Generate2D( data_2d , ps ); for( unsigned k = 0 ; k < ps ; ++k ) { int two_k = 2*k; samples[k].bsdf_sample[1].t = data_1d[k]; samples[k].bsdf_sample[1].u = data_2d[two_k]; samples[k].bsdf_sample[1].v = data_2d[two_k+1]; } sampler->Generate1D( data_1d , ps ); sampler->Generate2D( data_2d , ps ); for( unsigned k = 0 ; k < ps ; ++k ) { int two_k = 2*k; samples[k].light_sample[0].t = data_1d[k]; samples[k].light_sample[0].u = data_2d[two_k]; samples[k].light_sample[0].v = data_2d[two_k+1]; } }else { for (unsigned k = 0; k < ps; ++k) { samples[k].bsdf_sample[0] = BsdfSample(true); samples[k].bsdf_sample[1] = BsdfSample(true); samples[k].light_sample[0] = LightSample(true); } } }
// Preprocess void InstantRadiosity::PreProcess() { m_pVirtualLightSources = new list<VirtualLightSource>[m_nLightPathSet]; for( int k = 0 ; k < m_nLightPathSet ; ++k ) { for( int i = 0 ; i < m_nLightPaths ; ++i ) { // pick a light first float light_pick_pdf; const Light* light = scene.SampleLight( sort_canonical() , &light_pick_pdf ); // sample a ray from the light source float light_emission_pdf = 0.0f; float light_pdfa = 0.0f; Ray ray; float cosAtLight = 1.0f; Spectrum le = light->sample_l( LightSample(true) , ray , &light_emission_pdf , &light_pdfa , &cosAtLight ); Spectrum throughput = le * cosAtLight / ( light_pick_pdf * light_emission_pdf ); int current_depth = 0; Intersection intersect; while( true ) { if (false == scene.GetIntersect(ray, &intersect)) break; VirtualLightSource ls; ls.power = throughput; ls.intersect = intersect; ls.wi = -ray.m_Dir; ls.depth = ++current_depth; m_pVirtualLightSources[k].push_back( ls ); float bsdf_pdf; Vector wo; Bsdf* bsdf = intersect.primitive->GetMaterial()->GetBsdf(&intersect); Spectrum bsdf_value = bsdf->sample_f(ls.wi, wo, BsdfSample(true), &bsdf_pdf, BXDF_ALL); if( bsdf_pdf == 0.0f ) break; // apply russian roulette float continueProperbility = min( 1.0f , throughput.GetIntensity() ); if( sort_canonical() > continueProperbility ) break; throughput /= continueProperbility; // update throughput throughput *= bsdf_value * ( AbsDot(wo, intersect.normal) / bsdf_pdf ); // update next ray ray = Ray(intersect.intersect, wo, 0, 0.001f); } } } }
// radiance along a specific ray direction Spectrum DirectLight::Li( const Ray& r , const PixelSample& ps ) const { if( r.m_Depth > max_recursive_depth ) return 0.0f; // get the intersection between the ray and the scene Intersection ip; // evaluate light directly if( false == scene.GetIntersect( r , &ip ) ) return scene.Le( r ); Spectrum li = ip.Le( -r.m_Dir ); // eavluate direct light unsigned light_num = scene.LightNum(); for( unsigned i = 0 ; i < light_num ; ++i ) { const Light* light = scene.GetLight(i); li += EvaluateDirect( r , scene , light , ip , LightSample(true) , BsdfSample(true), BXDF_TYPE( BXDF_ALL ) ); } return li; }
// private method of li Spectrum InstantRadiosity::_li( const Ray& r , bool ignoreLe , float* first_intersect_dist ) const { // return if it is larger than the maximum depth if( r.m_Depth > max_recursive_depth ) return 0.0f; // get intersection from camera ray Intersection ip; if( false == scene.GetIntersect( r , &ip ) ) return ignoreLe?0.0f:scene.Le( r ); // eavluate light path less than two vertices Spectrum radiance = ignoreLe?0.0f:ip.Le( -r.m_Dir ); unsigned light_num = scene.LightNum(); for( unsigned i = 0 ; i < light_num ; ++i ) { const Light* light = scene.GetLight(i); radiance += EvaluateDirect( r , scene , light , ip , LightSample(true) , BsdfSample(true) , BXDF_TYPE( BXDF_ALL ) ); } if( first_intersect_dist ) *first_intersect_dist = ip.t; // pick a virtual light source randomly const unsigned lps_id = min( m_nLightPathSet - 1 , (int)(sort_canonical() * m_nLightPathSet) ); list<VirtualLightSource> vps = m_pVirtualLightSources[lps_id]; Bsdf* bsdf = ip.primitive->GetMaterial()->GetBsdf(&ip); // evaluate indirect illumination Spectrum indirectIllum; list<VirtualLightSource>::const_iterator it = vps.begin(); while( it != vps.end() ) { if( r.m_Depth + it->depth > max_recursive_depth ) { ++it; continue; } Vector delta = ip.intersect - it->intersect.intersect; float sqrLen = delta.SquaredLength(); float len = sqrt( sqrLen ); Vector n_delta = delta / len; Bsdf* bsdf1 = it->intersect.primitive->GetMaterial()->GetBsdf(&(it->intersect)); float gterm = AbsDot( n_delta , ip.normal ) * AbsDot( n_delta , it->intersect.normal ) / max( m_fMinSqrDist , sqrLen ); Spectrum f0 = bsdf->f( -r.m_Dir , -n_delta ); Spectrum f1 = bsdf1->f( n_delta , it->wi ); Spectrum contr = gterm * f0 * f1 * it->power; if( !contr.IsBlack() ) { Visibility vis(scene); vis.ray = Ray( it->intersect.intersect , n_delta , 0 , 0.001f , len - 0.001f ); if( vis.IsVisible() ) indirectIllum += contr; } ++it; } radiance += indirectIllum / (float)m_nLightPaths; if( m_fMinDist > 0.0f ) { Vector wi; float bsdf_pdf; Spectrum f = bsdf->sample_f( -r.m_Dir , wi , BsdfSample( true ) , &bsdf_pdf ); if( !f.IsBlack() && bsdf_pdf != 0.0f ) { PixelSample ps; float gather_dist; Ray gather_ray( ip.intersect , wi , r.m_Depth + 1 , 0.001f , m_fMinDist - 0.001f ); Spectrum li = _li( gather_ray , true , &gather_dist ); if( !li.IsBlack() ) { float dgterm = AbsDot( wi , ip.normal ) * max( 0.0f , 1.0f - gather_dist * gather_dist / m_fMinSqrDist ); radiance += f * li * dgterm / bsdf_pdf; } } } return radiance; }
// return the radiance of a specific direction // note : there are one factor makes the method biased. // there is a limitation on the number of vertexes in the path Spectrum PathTracing::Li( const Ray& ray , const PixelSample& ps ) const { Spectrum L = 0.0f; Spectrum throughput = 1.0f; int bounces = 0; Ray r = ray; while(true) { Intersection inter; // get the intersection between the ray and the scene // if it's a light , accumulate the radiance and break if( false == scene.GetIntersect( r , &inter ) ) { if( bounces == 0 ) return scene.Le( r ); break; } if( bounces == 0 ) L+=inter.Le(-r.m_Dir); // make sure there is intersected primitive Sort_Assert( inter.primitive != 0 ); // evaluate the light Bsdf* bsdf = inter.primitive->GetMaterial()->GetBsdf(&inter); float light_pdf = 0.0f; LightSample light_sample = (bounces==0)?ps.light_sample[0]:LightSample(true); BsdfSample bsdf_sample = (bounces==0)?ps.bsdf_sample[0]:BsdfSample(true); const Light* light = scene.SampleLight( light_sample.t , &light_pdf ); if( light_pdf > 0.0f ) L += throughput * EvaluateDirect( r , scene , light , inter , light_sample , bsdf_sample , BXDF_TYPE(BXDF_ALL) ) / light_pdf; // sample the next direction using bsdf float path_pdf; Vector wi; BXDF_TYPE bxdf_type; Spectrum f; BsdfSample _bsdf_sample = (bounces==0)?ps.bsdf_sample[1]:BsdfSample(true); f = bsdf->sample_f( -r.m_Dir , wi , _bsdf_sample , &path_pdf , BXDF_ALL , &bxdf_type ); if( f.IsBlack() || path_pdf == 0.0f ) break; // update path weight throughput *= f * AbsDot( wi , inter.normal ) / path_pdf; if( throughput.GetIntensity() == 0.0f ) break; if( bounces > 4 ) { float continueProperbility = min( 0.5f , throughput.GetIntensity() ); if( sort_canonical() > continueProperbility ) break; throughput /= continueProperbility; } r.m_Ori = inter.intersect; r.m_Dir = wi; r.m_fMin = 0.001f; ++bounces; // note : the following code makes the method biased // 'path_per_pixel' could be set very large to reduce the side-effect. if( bounces >= max_recursive_depth ) break; } return L; }