VectorSetAnalysis.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "VectorTypes.h"
 
namespace UE
{
namespace Geometry
{
 
using namespace UE::Math;
 
template<typename RealType>
class TVectorSetAnalysis3
{
public:
    //
    // Input data
    //
 
    TArray<TVector<RealType>> Vectors;
    TArray<int32> VectorIDs;
    bool bNormalized = false;
 
    //
    // Calculated values
    //
 
    TArray<TVector<RealType>> ClusterVectors;
    TArray<int32> VectorToClusterMap;
 
 
    template<typename EnumerableIDType>
    void Initialize(EnumerableIDType EnumerableIDs, TFunctionRef<TVector<RealType>(int32)> GetVectorFunc, int32 NumVectorsHint = 0, bool bIsNormalizedHint = false)
    {
        Vectors.Reserve(NumVectorsHint);
        VectorIDs.Reserve(NumVectorsHint);
        for (int32 ID : EnumerableIDs)
        {
            VectorIDs.Add(ID);
            Vectors.Add(GetVectorFunc(ID));
        }
 
        bNormalized = bIsNormalizedHint;
    }
 
    int32 NumVectors() const { return Vectors.Num(); }
 
    int32 NumClusters() const { return ClusterVectors.Num(); }
 
 
    inline void GreedyClusterVectors(RealType AngleToleranceDeg)
    {
        check(bNormalized);     // otherwise code below is incorrect
 
        RealType DotTolerance = TMathUtil<RealType>::Cos(AngleToleranceDeg * TMathUtil<RealType>::DegToRad);
 
        int32 N = NumVectors(), M = 0;
        VectorToClusterMap.SetNum(N);
        for (int32 k = 0; k < N; ++k)
        {
            bool bFound = false;
            if (M > 0)
            {
                // try to find an existing cluster
                for (int32 j = 0; j < M && !bFound; ++j)
                {
                    if (Vectors[k].Dot(ClusterVectors[j]) > DotTolerance)
                    {
                        VectorToClusterMap[k] = j;
                        bFound = true;
                    }
                }
            }
 
            // cluster not found, spawn a new one
            if (!bFound)
            {
                ClusterVectors.Add(Vectors[k]);
                VectorToClusterMap[k] = k;
                M++;
            }
        }
    }
 
 
};
 
typedef TVectorSetAnalysis3<float> FVectorSetAnalysis3f;
typedef TVectorSetAnalysis3<double> FVectorSetAnalysis3d;
 
} // end namespace UE::Geometry
} // end namespace UE