Microfacet.h

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#pragma once
 
#include "Math/TVector3.h"
#include "Core/SurfaceHit.h"
#include "Core/LTA/PDF.h"
 
#include <Common/primitive_type.h>
 
#include <array>
 
namespace ph
{
 
class Microfacet
{
public:
    virtual ~Microfacet() = default;
 
    virtual real distribution(
        const SurfaceHit& X,
        const math::Vector3R& N,
        const math::Vector3R& H) const = 0;
 
    virtual real geometry(
        const SurfaceHit& X,
        const math::Vector3R& N,
        const math::Vector3R& H,
        const math::Vector3R& L,
        const math::Vector3R& V) const = 0;
 
    virtual void sampleH(
        const SurfaceHit& X,
        const math::Vector3R& N,
        const std::array<real, 2>& sample,
        math::Vector3R* out_H) const = 0;
 
    virtual lta::PDF pdfSampleH(
        const SurfaceHit& X,
        const math::Vector3R& N,
        const math::Vector3R& H) const = 0;
 
    virtual void sampleVisibleH(
        const SurfaceHit& X,
        const math::Vector3R& N,
        const math::Vector3R& V,
        const std::array<real, 2>& sample,
        math::Vector3R* out_H) const;
 
    virtual lta::PDF pdfSampleVisibleH(
        const SurfaceHit& X,
        const math::Vector3R& N,
        const math::Vector3R& H,
        const math::Vector3R& V) const;
 
protected:
    static bool isSidednessAgreed(
        real NoD,
        real HoD);
 
    static bool isSidednessAgreed(
        real NoL,
        real NoV,
        real HoL,
        real HoV);
};
 
inline void Microfacet::sampleVisibleH(
    const SurfaceHit& X,
    const math::Vector3R& N,
    const math::Vector3R& /* V */,
    const std::array<real, 2>& sample,
    math::Vector3R* const out_H) const
{
    return sampleH(X, N, sample, out_H);
}
 
inline lta::PDF Microfacet::pdfSampleVisibleH(
    const SurfaceHit& X,
    const math::Vector3R& N,
    const math::Vector3R& H,
    const math::Vector3R& /* V */) const
{
    return pdfSampleH(X, N, H);
}
 
inline bool Microfacet::isSidednessAgreed(
    const real NoD,
    const real HoD)
{
    return HoD * NoD > 0.0_r;
}
 
inline bool Microfacet::isSidednessAgreed(
    const real NoL,
    const real NoV,
    const real HoL,
    const real HoV)
{
    return isSidednessAgreed(NoL, HoL) && isSidednessAgreed(NoV, HoV);
}
 
}// end namespace ph