MeshUtilitiesCommon.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
 
enum class ELightmapUVVersion : int32
{
    BitByBit = 0,
    Segments = 1,
    SmallChartPacking = 2,
    ScaleChartsOrderingFix = 3,
    ChartJoiningLFix = 4,
    Allocator2DFlipFix = 5,
    ConsiderLightmapPadding = 6,
    ForceLightmapPadding = 7,
    Segments2D = 8,
    OptimalSurfaceArea = 9,
    ScaleByEdgesLength = 10,
    Latest = ScaleByEdgesLength
};
 
struct FBoneVertInfo
{
    // Invariant: Arrays should be same length!
    TArray<FVector3f>   Positions;
    TArray<FVector3f>   Normals;
};
 
struct FIndexAndZ
{
    float Z;
    int32 Index;
 
    FIndexAndZ() {}
 
    FIndexAndZ(int32 InIndex, FVector3f V)
    {
        Z = 0.30f * V.X + 0.33f * V.Y + 0.37f * V.Z;
        Index = InIndex;
    }
};
 
struct FCompareIndexAndZ
{
    inline bool operator()(FIndexAndZ const& A, FIndexAndZ const& B) const { return A.Z < B.Z; }
};
 
inline bool PointsEqual(const FVector3f& V1, const FVector3f& V2, float ComparisonThreshold)
{
    if (FMath::Abs(V1.X - V2.X) > ComparisonThreshold
        || FMath::Abs(V1.Y - V2.Y) > ComparisonThreshold
        || FMath::Abs(V1.Z - V2.Z) > ComparisonThreshold)
    {
        return false;
    }
    return true;
}
 
namespace TriangleUtilities
{
    /*
     * This function compute the area of a triangle, it will return zero if the triangle is degenerated
     */
    static float ComputeTriangleArea(const FVector3f& PointA, const FVector3f& PointB, const FVector3f& PointC)
    {
        return FVector3f::CrossProduct((PointB - PointA), (PointC - PointA)).Size() / 2.0f;
    }
 
    /*
     * This function compute the angle of a triangle corner, it will return zero if the triangle is degenerated
     */
    static float ComputeTriangleCornerAngle(const FVector3f& PointA, const FVector3f& PointB, const FVector3f& PointC)
    {
        FVector3f E1 = (PointB - PointA);
        FVector3f E2 = (PointC - PointA);
        //Normalize both edges (unit vector) of the triangle so we get a dotProduct result that will be a valid acos input [-1, 1]
        if (!E1.Normalize() || !E2.Normalize())
        {
            //Return a null ratio if the polygon is degenerate
            return 0.0f;
        }
        float DotProduct = FVector3f::DotProduct(E1, E2);
        return FMath::Acos(DotProduct);
    }
}
 
inline FMatrix44f GetTangentBasisFrisvad(FVector3f TangentZ)
{
    FVector3f TangentX;
    FVector3f TangentY;
 
    if (TangentZ.Z < -0.9999999f)
    {
        TangentX = FVector3f(0, -1, 0);
        TangentY = FVector3f(-1, 0, 0);
    }
    else
    {
        float A = 1.0f / (1.0f + TangentZ.Z);
        float B = -TangentZ.X * TangentZ.Y * A;
        TangentX = FVector3f(1.0f - TangentZ.X * TangentZ.X * A, B, -TangentZ.X);
        TangentY = FVector3f(B, 1.0f - TangentZ.Y * TangentZ.Y * A, -TangentZ.Y);
    }
 
    FMatrix44f LocalBasis;
    LocalBasis.SetIdentity();
    LocalBasis.SetAxis(0, TangentX);
    LocalBasis.SetAxis(1, TangentY);
    LocalBasis.SetAxis(2, TangentZ);
    return LocalBasis;
}