BfConstant.h

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#pragma once
 
#include "Core/VolumeBehavior/BlockFunction.h"
#include "Core/SurfaceHit.h"
#include "Math/Color/Spectrum.h"
 
#include <Common/assertion.h>
 
#include <cmath>
#include <string>
 
namespace ph
{
 
class BfConstant final : public BlockFunction
{
public:
    inline BfConstant() :
        BfConstant(math::Spectrum(0))
    {}
 
    inline BfConstant(const math::Spectrum& coeff) :
        BlockFunction(),
        m_absorptionCoeff(coeff)
    {}
 
    virtual inline ~BfConstant() override = default;
 
    virtual inline void evalAbsorptionCoeff(
        const SurfaceHit&     /* X */, 
        math::Spectrum* const out_coeff) const override
    {
        PH_ASSERT(out_coeff);
 
        *out_coeff = m_absorptionCoeff;
    }
 
    inline math::Spectrum calcTransmittance(const real dist) const
    {
        PH_ASSERT_MSG(dist >= 0.0_r, 
            "dist = " + std::to_string(dist));
 
        math::Spectrum transmittance;
        for(std::size_t i = 0; i < math::Spectrum::NUM_VALUES; ++i)
        {
            transmittance[i] = std::exp(-m_absorptionCoeff[i] * dist);
        }
        return transmittance;
    }
 
private:
    math::Spectrum m_absorptionCoeff;
};
 
}// end namespace ph