RotationAboutPointMatrix.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreTypes.h"
#include "Math/Vector.h"
#include "Math/Matrix.h"
#include "Math/Quat.h"
#include "Math/RotationTranslationMatrix.h"
 
namespace UE {
namespace Math {
 
template<typename T>    
struct TRotationAboutPointMatrix
    : public TRotationTranslationMatrix<T>
{
public:
    using TRotationTranslationMatrix<T>::M;
 
    [[nodiscard]] TRotationAboutPointMatrix(const TRotator<T>& Rot, const TVector<T>& Origin);
 
    // Conversion to other type.
    template<typename FArg UE_REQUIRES(!std::is_same_v<T, FArg>)>
    [[nodiscard]] explicit TRotationAboutPointMatrix(const TRotationAboutPointMatrix<FArg>& From)
        : TRotationTranslationMatrix<T>(From)
    {
    }
 
    [[nodiscard]] static TMatrix<T> Make(const TRotator<T>& Rot, const TVector<T>& Origin)
    {
        return TRotationAboutPointMatrix(Rot, Origin);
    }
 
    [[nodiscard]] static TMatrix<T> Make(const TQuat<T>& Rot, const TVector<T>& Origin)
    {
        return TRotationAboutPointMatrix(Rot.Rotator(), Origin);
    }
};
 
template<typename T>
inline TRotationAboutPointMatrix<T>::TRotationAboutPointMatrix(const TRotator<T>& Rot, const TVector<T>& Origin)
    : TRotationTranslationMatrix<T>(Rot, Origin)
{
    // FRotationTranslationMatrix generates R * T.
    // We need -T * R * T, so prepend that translation:
    TVector<T> XAxis(M[0][0], M[1][0], M[2][0]);
    TVector<T> YAxis(M[0][1], M[1][1], M[2][1]);
    TVector<T> ZAxis(M[0][2], M[1][2], M[2][2]);
 
    M[3][0] -= XAxis | Origin;
    M[3][1] -= YAxis | Origin;
    M[3][2] -= ZAxis | Origin;
}
 
} // namespace Math
} // namespace UE
 
UE_DECLARE_LWC_TYPE(RotationAboutPointMatrix, 44);
 
template<> struct TIsUECoreVariant<FRotationAboutPointMatrix44f> { enum { Value = true }; };
template<> struct TIsUECoreVariant<FRotationAboutPointMatrix44d> { enum { Value = true }; };