PolyVoxCore/include/PolyVoxCore/CubicSurfaceExtractor.h

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Copyright (c) 2005-2009 David Williams

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#ifndef __PolyVox_CubicSurfaceExtractor_H__
#define __PolyVox_CubicSurfaceExtractor_H__

#include "PolyVoxImpl/TypeDef.h"

#include "PolyVoxCore/Array.h"
#include "PolyVoxCore/SurfaceMesh.h"

namespace PolyVox
{
    template< template<typename> class VolumeType, typename VoxelType>
    class CubicSurfaceExtractor
    {
        struct IndexAndMaterial
        {
            int32_t iIndex;
            int32_t uMaterial; //Should actually use the material type here, but this is ok for now.
        };

        enum FaceNames
        {
            PositiveX,
            PositiveY,
            PositiveZ,
            NegativeX,
            NegativeY,
            NegativeZ,
            NoOfFaces
        };

        struct Quad
        {
            uint32_t vertices[4];
        };

    public:
        CubicSurfaceExtractor(VolumeType<VoxelType>* volData, Region region, SurfaceMesh<PositionMaterial>* result, bool bMergeQuads = true);

        void execute();     

    private:
        int32_t addVertex(float fX, float fY, float fZ, uint32_t uMaterial, Array<3, IndexAndMaterial>& existingVertices);
        bool performQuadMerging(std::list<Quad>& quads);
        bool mergeQuads(Quad& q1, Quad& q2);

        //The volume data and a sampler to access it.
        VolumeType<VoxelType>* m_volData;

        //Information about the region we are currently processing
        Region m_regSizeInVoxels;

        //The surface patch we are currently filling.
        SurfaceMesh<PositionMaterial>* m_meshCurrent;

        //Used to avoid creating duplicate vertices.
        Array<3, IndexAndMaterial> m_previousSliceVertices;
        Array<3, IndexAndMaterial> m_currentSliceVertices;

        //During extraction we create a number of different lists of quads. All the 
        //quads in a given list are in the same plane and facing in the same direction.
        std::vector< std::list<Quad> > m_vecQuads[NoOfFaces];

        //Controls whether quad merging should be performed. This might be undesirable
        //is the user needs per-vertex attributes, or to perform per vertex lighting.
        bool m_bMergeQuads;

        //Although we try to avoid creating multiple vertices at the same location, sometimes this is unavoidable
        //if they have different materials. For example, four different materials next to each other would mean
        //four quads (though more triangles) sharing the vertex. As far as I can tell, four is the worst case scenario.
        static const uint32_t MaxQuadsSharingVertex;        
    };
}

#include "PolyVoxCore/CubicSurfaceExtractor.inl"

#endif