RotationAboutPointMatrix.h

Go to the documentation of this file.

// 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 {
 
/** Rotates about an Origin point. */
template<typename T>
struct TRotationAboutPointMatrix
    : public TRotationTranslationMatrix<T>
{
public:
    using TRotationTranslationMatrix<T>::M;
 
    /**
     * Constructor.
     *
     * @param Rot rotation
     * @param Origin about which to rotate.
     */
    TRotationAboutPointMatrix(const TRotator<T>& Rot, const TVector<T>& Origin);
 
    // Conversion to other type.
    template<typename FArg, TEMPLATE_REQUIRES(!std::is_same_v<T, FArg>)>
    explicit TRotationAboutPointMatrix(const TRotationAboutPointMatrix<FArg>& From) : TRotationTranslationMatrix<T>(From) {}
 
    /** Matrix factory. Return an TMatrix<T> so we don't have type conversion issues in expressions. */
    static TMatrix<T> Make(const TRotator<T>& Rot, const TVector<T>& Origin)
    {
        return TRotationAboutPointMatrix(Rot, Origin);
    }
 
    /** Matrix factory. Return an TMatrix<T> so we don't have type conversion issues in expressions. */
    static TMatrix<T> Make(const TQuat<T>& Rot, const TVector<T>& Origin)
    {
        return TRotationAboutPointMatrix(Rot.Rotator(), Origin);
    }
};
 
template<typename T>
FORCEINLINE 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 }; };