LODGenerator.h

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#pragma once

#include "Utilities/ObjectLoader/ObjectLoader.h"
#include "Utilities/STL/MxMap.h"
#include "Utilities/STL/MxHashMap.h"

namespace MxEngine
{
    struct Vector3Cmp
    {
        inline static float Threshold = 100.0f;

        static bool EqF(float x, float y)
        {
            return std::abs(x - y) <= Threshold;
        }

        static bool LessF(float x, float y) 
        {
            return y - x >= Threshold;
        }

        bool operator()(const Vector3& v1, const Vector3& v2) const
        {
            if (EqF(v1.x, v2.x))
                if (EqF(v1.y, v2.y))
                    return LessF(v1.z, v2.z);
                else
                    return LessF(v1.y, v2.y);
            else
                return LessF(v1.x, v2.x);
        }
    };

    class LODGenerator
    {
        const MeshData& mesh;

        using ProjectionTable = MxVector<uint32_t>;
        using WeightList = MxHashMap<size_t, size_t>;
        ProjectionTable projection;
        MxVector<WeightList> weights;

        size_t CollapseDublicate(MxMap<Vector3, size_t, Vector3Cmp>& vertexMapping, size_t f);
        /*
        generates submesh projection and weight tables, collapses vertex duplicates which are close enough to each other
        \param threshold minimal value in vertecies components from which vertecies are considered equal (see Vector3Cmp comparator)
        */
        void PrepareIndexData(float threshold);
    public:
        LODGenerator(const MeshData& mesh);
        MeshData CreateObject(float threshold);
    };
}