RenderMath.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "PackedNormal.h"
 
inline float GetBasisDeterminantSign(const FVector& XAxis, const FVector& YAxis, const FVector& ZAxis)
{
    FMatrix Basis(
        FPlane(XAxis, 0),
        FPlane(YAxis, 0),
        FPlane(ZAxis, 0),
        FPlane(0, 0, 0, 1)
    );
    // RotDeterminant is the determinant of the upper left 3x3 matrix and equivalent to the full 4x4 determinant for this matrix
    // at one fourth the cost. 
    return (Basis.RotDeterminant() < 0) ? -1.0f : +1.0f;
}
 
inline int8 GetBasisDeterminantSignByte(const FPackedNormal& XAxis, const FPackedNormal& YAxis, const FPackedNormal& ZAxis)
{
    return GetBasisDeterminantSign(XAxis.ToFVector(), YAxis.ToFVector(), ZAxis.ToFVector()) < 0 ? -127 : 127;
}
 
template<typename VectorType>
inline FVector GenerateYAxis(const VectorType& XAxis, const VectorType& ZAxis)
{
    static_assert(std::is_same_v<VectorType, FPackedNormal> ||
        std::is_same_v<VectorType, FPackedRGBA16N>, "ERROR: Must be FPackedNormal or FPackedRGBA16N");
    FVector  x = XAxis.ToFVector();
    FVector4 z = ZAxis.ToFVector4();
    return (FVector(z) ^ x) * z.W;
}