RussianRoulette.h

Go to the documentation of this file.

#pragma once
 
#include "Math/Color/Spectrum.h"
#include "Math/math.h"
#include "Core/SampleGenerator/SampleFlow.h"
 
#include <Common/assertion.h>
#include <Common/primitive_type.h>
 
namespace ph::lta
{
 
class RussianRoulette final
{
public:
    bool surviveOnLuminance(
        const math::Spectrum& s,
        SampleFlow& sampleFlow,
        real* out_survivalProbability) const;
};
 
inline bool RussianRoulette::surviveOnLuminance(
    const math::Spectrum& s,
    SampleFlow& sampleFlow,
    real* const out_survivalProbability) const
{
    PH_ASSERT(out_survivalProbability);
 
    // Survival rate is not allowed to be 100% to avoid immortal rays (e.g., TIR);
    // the rate should also kill non-finite luminance as this is a good place to do it
    const real rrSurvivalRate = math::safe_clamp(s.relativeLuminance(), 0.0_r, 0.95_r);
    const real rrSpin = sampleFlow.flow1D();// FIXME: use something like sampleFlow.binaryPick()
 
    // Survived
    if(rrSpin < rrSurvivalRate)
    {
        PH_ASSERT(0.0_r < rrSurvivalRate && rrSurvivalRate <= 1.0_r);
 
        *out_survivalProbability = rrSurvivalRate;
        return true;
    }
    // Dead
    else
    {
        return false;
    }
}
 
}// end namespace ph::lta