Spectrum PathTracer::Integration (
const Scene * thisScene,
const Ray & ray,
size_t currentDepth
) const
{
// Russian Roulette
// probility to stop this path
double rr = 0.01;
double randnum = getUniformRandomNumber( 0.0, 0.99 );
if ( randnum < rr && currentDepth > 5 )
return Spectrum();
if ( currentDepth == maxDepth )
return Spectrum();
Intersection intersectionInfo;
// check intersection between ray and scene
if ( ! thisScene->IntersectionWithScene( ray, intersectionInfo ) )
return Spectrum();
// if there is an intersection
Spectrum intensity;
Spectrum emission;
Objects * obj = intersectionInfo.object;
if ( obj->emitter )
{
emission = obj->emission;
}
BRDFModels * brdf = obj->brdf_model;
// Get surface (macro) normal direction
Vector geometryNormalDirection ( 0 , 0 , 0 );
Vector sampledNextDirection ( 0 , 0 , 0 );
geometryNormalDirection = intersectionInfo.normal;
double pdf = 0;
Attenuation attenuationFactor =
brdf->SampleBRDF(
ray.direction,
sampledNextDirection,
geometryNormalDirection,
pdf
);
Ray newRay(
intersectionInfo.intersectionPoint,
sampledNextDirection
);
Spectrum Li =
Integration(
thisScene,
newRay,
currentDepth + 1
);
if ( !Li.isEmpty() )
{
attenuationFactor.Scaled_by_Spectrum_Value( obj->material_type->color );
double cos_i = AbsDot( sampledNextDirection, geometryNormalDirection );
intensity +=
Attenuate_Light_Spectrum( attenuationFactor, Li ) * cos_i / pdf;
}
// weight the radiance back after Ruassian Roulette
intensity = ( currentDepth > 5 ) ? ( intensity / ( 1 - rr ) ) : intensity;
ASSERT_NAN( intensity );
return emission + intensity;
}
// with direct illumination
// this one actually does not do the right things on DI with MIS
// left only for reference
Spectrum PathTracer::IntegrationWithDI (
const Scene * thisScene,
const Ray & ray,
size_t currentDepth
) const
{
// Russian Roulette
// probility to stop this path
double rr = 0.01;
double randnum = getUniformRandomNumber( 0.0, 1.0 );
if ( randnum < rr && currentDepth > 5 )
return Spectrum();
if ( currentDepth == maxDepth )
return Spectrum();
Intersection intersectionInfo;
// check intersection between ray and scene
if ( !thisScene->IntersectionWithScene( ray, intersectionInfo ) )
return Spectrum();
// if there is an intersection
Spectrum intensity;
Spectrum lightSourceSamplingContribution;
Spectrum brdfSamplingContribution;
double brdf_pdf = 0;
double light_pdf = 0;
double brdf_weight = 0;
double light_weight = 0;
Objects * obj = intersectionInfo.object;
if ( obj->emitter )
{
intensity += obj->emission;
}
BRDFModels * brdf = obj->brdf_model;
// **************** evaluate direction illumination ******
if ( !obj->emitter )
EstimateDirectIllumination(
thisScene,
& intersectionInfo,
ray,
light_pdf,
lightSourceSamplingContribution
);
// ******************** end of direct illumination **********************
// BRDF sampling is evaluated twice????
Vector geometryNormalDirection;
geometryNormalDirection = intersectionInfo.normal;
Vector sampledNextDirection( 0, 0, 0 );
Attenuation attenuationFactor;
attenuationFactor = brdf->SampleBRDF(
ray.direction,
sampledNextDirection,
geometryNormalDirection,
brdf_pdf
);
Ray newRay(
intersectionInfo.intersectionPoint,
sampledNextDirection
);
Spectrum Li =
IntegrationWithDI(
thisScene,
newRay,
currentDepth + 1
);
if ( !Li.isEmpty() )
{
attenuationFactor.Scaled_by_Spectrum_Value( obj->material_type->color );
double cos_i = AbsDot( sampledNextDirection, geometryNormalDirection );
brdfSamplingContribution += Attenuate_Light_Spectrum( attenuationFactor, Li ) * cos_i;
}
if ( light_pdf == 0 && brdf_pdf == 0 )
{
return intensity;
}
// MIS weight
BalanceHeuristic( 1, light_pdf, 1, brdf_pdf, light_weight, brdf_weight );
intensity += lightSourceSamplingContribution * light_weight;
intensity += brdfSamplingContribution * brdf_weight;
intensity = ( currentDepth > 5 ) ? ( intensity / ( 1 - rr ) ) : intensity;
ASSERT_NAN( intensity );
return intensity;
}