TDisk.ipp

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#pragma once
 
#include "Math/Geometry/TDisk.h"
#include "Math/TOrthonormalBasis3.h"
 
namespace ph::math
{
 
template<typename T>
inline TDisk<T> TDisk<T>::makeUnit()
{
    return TDisk(1);
}
 
template<typename T>
inline TDisk<T>::TDisk(const T radius) : 
    m_radius(radius)
{
    PH_ASSERT_GT(radius, static_cast<T>(0));
}
 
template<typename T>
inline T TDisk<T>::getArea() const
{
    return constant::pi<T> * m_radius * m_radius;
}
 
template<typename T>
inline TVector3<T> TDisk<T>::sampleToSurface(const std::array<T, 2>& sample) const
{
    const auto surfacePos2D = sampleToSurface2D(sample);
    return TVector3<T>(surfacePos2D.y, static_cast<T>(0), surfacePos2D.x);
}
 
template<typename T>
inline TVector3<T> TDisk<T>::sampleToSurface(const std::array<T, 2>& sample, T* const out_pdfA) const
{
    const auto surfacePos2D = sampleToSurface2D(sample, out_pdfA);
    return TVector3<T>(surfacePos2D.y, static_cast<T>(0), surfacePos2D.x);
}
 
template<typename T>
inline TVector2<T> TDisk<T>::sampleToSurface2D(const std::array<T, 2>& sample) const
{
    PH_ASSERT_IN_RANGE_INCLUSIVE(sample[0], static_cast<T>(0), static_cast<T>(1));
    PH_ASSERT_IN_RANGE_INCLUSIVE(sample[1], static_cast<T>(0), static_cast<T>(1));
    PH_ASSERT_GE(m_radius, static_cast<T>(0));
 
    const T r   = std::sqrt(sample[0]);
    const T phi = constant::two_pi<real> * sample[1];
 
    const auto localUnitPos = TVector2<T>(
        r * std::cos(phi),
        r * std::sin(phi));
 
    return localUnitPos.mul(m_radius);
}
 
template<typename T>
inline TVector2<T> TDisk<T>::sampleToSurface2D(const std::array<T, 2>& sample, T* const out_pdfA) const
{
    PH_ASSERT(out_pdfA);
    *out_pdfA = uniformSamplePdfA();
 
    return sampleToSurface2D(sample);
}
 
template<typename T>
inline TVector3<T> TDisk<T>::sampleToSurfaceOriented(
    const std::array<T, 2>& sample,
    const TVector3<T>&      normal,
    const TVector3<T>&      offset) const
{
    const auto& diskPos2d = sampleToSurface2D(sample);
    const auto& basis     = TOrthonormalBasis3<T>::makeFromUnitY(normal);
 
    return (basis.getZAxis() * diskPos2d.x) + 
           (basis.getXAxis() * diskPos2d.y) + 
           offset;
}
 
template<typename T>
inline TVector3<T> TDisk<T>::sampleToSurfaceOriented(
    const std::array<T, 2>& sample,
    T* const                out_pdfA,
    const TVector3<T>&      normal,
    const TVector3<T>&      offset) const
{
    PH_ASSERT(out_pdfA);
    *out_pdfA = uniformSamplePdfA();
 
    return sampleToSurfaceOriented(sample, normal, offset);
}
 
template<typename T>
inline T TDisk<T>::uniformSamplePdfA() const
{
    // PDF_A is 1/(pi*r^2)
    return static_cast<T>(1) / getArea();
}
 
}// end namespace ph::math