PolyVoxCore/include/PolyVoxCore/SurfaceExtractor.h

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/*******************************************************************************
Copyright (c) 2005-2009 David Williams

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Permission is granted to anyone to use this software for any purpose,
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#ifndef __PolyVox_SurfaceExtractor_H__
#define __PolyVox_SurfaceExtractor_H__

#include "PolyVoxImpl/MarchingCubesTables.h"
#include "PolyVoxImpl/TypeDef.h"

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

namespace PolyVox
{
    template< template<typename> class VolumeType, typename VoxelType>
    class SurfaceExtractor
    {
    public:
        SurfaceExtractor(VolumeType<VoxelType>* volData, Region region, SurfaceMesh<PositionMaterialNormal>* result);

        void execute();

    private:
        //Compute the cell bitmask for a particular slice in z.
        template<bool isPrevZAvail>
        uint32_t computeBitmaskForSlice(const Array2DUint8& pPreviousBitmask, Array2DUint8& pCurrentBitmask);

        //Compute the cell bitmask for a given cell.
        template<bool isPrevXAvail, bool isPrevYAvail, bool isPrevZAvail>
        void computeBitmaskForCell(const Array2DUint8& pPreviousBitmask, Array2DUint8& pCurrentBitmask);

        //Use the cell bitmasks to generate all the vertices needed for that slice
        void generateVerticesForSlice(const Array2DUint8& pCurrentBitmask,
            Array2DInt32& m_pCurrentVertexIndicesX,
            Array2DInt32& m_pCurrentVertexIndicesY,
            Array2DInt32& m_pCurrentVertexIndicesZ);

        // NOTE: These two functions are in the .h file rather than the .inl due to an apparent bug in VC2010.
        //See http://stackoverflow.com/questions/1484885/strange-vc-compile-error-c2244 for details.
        Vector3DFloat computeCentralDifferenceGradient(const typename VolumeType<VoxelType>::Sampler& volIter)
        {
            //FIXME - Should actually use DensityType here, both in principle and because the maths may be
            //faster (and to reduce casts). So it would be good to add a way to get DensityType from a voxel.
            //But watch out for when the DensityType is unsigned and the difference could be negative.
            float voxel1nx = static_cast<float>(volIter.peekVoxel1nx0py0pz().getDensity());
            float voxel1px = static_cast<float>(volIter.peekVoxel1px0py0pz().getDensity());

            float voxel1ny = static_cast<float>(volIter.peekVoxel0px1ny0pz().getDensity());
            float voxel1py = static_cast<float>(volIter.peekVoxel0px1py0pz().getDensity());

            float voxel1nz = static_cast<float>(volIter.peekVoxel0px0py1nz().getDensity());
            float voxel1pz = static_cast<float>(volIter.peekVoxel0px0py1pz().getDensity());

            return Vector3DFloat
            (
                voxel1nx - voxel1px,
                voxel1ny - voxel1py,
                voxel1nz - voxel1pz
            );
        }

        Vector3DFloat computeSobelGradient(const typename VolumeType<VoxelType>::Sampler& volIter)
        {
            static const int weights[3][3][3] = {  {  {2,3,2}, {3,6,3}, {2,3,2}  },  {
                {3,6,3},  {6,0,6},  {3,6,3} },  { {2,3,2},  {3,6,3},  {2,3,2} } };

                //FIXME - Should actually use DensityType here, both in principle and because the maths may be
                //faster (and to reduce casts). So it would be good to add a way to get DensityType from a voxel.
                //But watch out for when the DensityType is unsigned and the difference could be negative.
                const float pVoxel1nx1ny1nz = static_cast<float>(volIter.peekVoxel1nx1ny1nz().getDensity());
                const float pVoxel1nx1ny0pz = static_cast<float>(volIter.peekVoxel1nx1ny0pz().getDensity());
                const float pVoxel1nx1ny1pz = static_cast<float>(volIter.peekVoxel1nx1ny1pz().getDensity());
                const float pVoxel1nx0py1nz = static_cast<float>(volIter.peekVoxel1nx0py1nz().getDensity());
                const float pVoxel1nx0py0pz = static_cast<float>(volIter.peekVoxel1nx0py0pz().getDensity());
                const float pVoxel1nx0py1pz = static_cast<float>(volIter.peekVoxel1nx0py1pz().getDensity());
                const float pVoxel1nx1py1nz = static_cast<float>(volIter.peekVoxel1nx1py1nz().getDensity());
                const float pVoxel1nx1py0pz = static_cast<float>(volIter.peekVoxel1nx1py0pz().getDensity());
                const float pVoxel1nx1py1pz = static_cast<float>(volIter.peekVoxel1nx1py1pz().getDensity());

                const float pVoxel0px1ny1nz = static_cast<float>(volIter.peekVoxel0px1ny1nz().getDensity());
                const float pVoxel0px1ny0pz = static_cast<float>(volIter.peekVoxel0px1ny0pz().getDensity());
                const float pVoxel0px1ny1pz = static_cast<float>(volIter.peekVoxel0px1ny1pz().getDensity());
                const float pVoxel0px0py1nz = static_cast<float>(volIter.peekVoxel0px0py1nz().getDensity());
                //const float pVoxel0px0py0pz = static_cast<float>(volIter.peekVoxel0px0py0pz().getDensity());
                const float pVoxel0px0py1pz = static_cast<float>(volIter.peekVoxel0px0py1pz().getDensity());
                const float pVoxel0px1py1nz = static_cast<float>(volIter.peekVoxel0px1py1nz().getDensity());
                const float pVoxel0px1py0pz = static_cast<float>(volIter.peekVoxel0px1py0pz().getDensity());
                const float pVoxel0px1py1pz = static_cast<float>(volIter.peekVoxel0px1py1pz().getDensity());

                const float pVoxel1px1ny1nz = static_cast<float>(volIter.peekVoxel1px1ny1nz().getDensity());
                const float pVoxel1px1ny0pz = static_cast<float>(volIter.peekVoxel1px1ny0pz().getDensity());
                const float pVoxel1px1ny1pz = static_cast<float>(volIter.peekVoxel1px1ny1pz().getDensity());
                const float pVoxel1px0py1nz = static_cast<float>(volIter.peekVoxel1px0py1nz().getDensity());
                const float pVoxel1px0py0pz = static_cast<float>(volIter.peekVoxel1px0py0pz().getDensity());
                const float pVoxel1px0py1pz = static_cast<float>(volIter.peekVoxel1px0py1pz().getDensity());
                const float pVoxel1px1py1nz = static_cast<float>(volIter.peekVoxel1px1py1nz().getDensity());
                const float pVoxel1px1py0pz = static_cast<float>(volIter.peekVoxel1px1py0pz().getDensity());
                const float pVoxel1px1py1pz = static_cast<float>(volIter.peekVoxel1px1py1pz().getDensity());

                const float xGrad(- weights[0][0][0] * pVoxel1nx1ny1nz -
                    weights[1][0][0] * pVoxel1nx1ny0pz - weights[2][0][0] *
                    pVoxel1nx1ny1pz - weights[0][1][0] * pVoxel1nx0py1nz -
                    weights[1][1][0] * pVoxel1nx0py0pz - weights[2][1][0] *
                    pVoxel1nx0py1pz - weights[0][2][0] * pVoxel1nx1py1nz -
                    weights[1][2][0] * pVoxel1nx1py0pz - weights[2][2][0] *
                    pVoxel1nx1py1pz + weights[0][0][2] * pVoxel1px1ny1nz +
                    weights[1][0][2] * pVoxel1px1ny0pz + weights[2][0][2] *
                    pVoxel1px1ny1pz + weights[0][1][2] * pVoxel1px0py1nz +
                    weights[1][1][2] * pVoxel1px0py0pz + weights[2][1][2] *
                    pVoxel1px0py1pz + weights[0][2][2] * pVoxel1px1py1nz +
                    weights[1][2][2] * pVoxel1px1py0pz + weights[2][2][2] *
                    pVoxel1px1py1pz);

                const float yGrad(- weights[0][0][0] * pVoxel1nx1ny1nz -
                    weights[1][0][0] * pVoxel1nx1ny0pz - weights[2][0][0] *
                    pVoxel1nx1ny1pz + weights[0][2][0] * pVoxel1nx1py1nz +
                    weights[1][2][0] * pVoxel1nx1py0pz + weights[2][2][0] *
                    pVoxel1nx1py1pz - weights[0][0][1] * pVoxel0px1ny1nz -
                    weights[1][0][1] * pVoxel0px1ny0pz - weights[2][0][1] *
                    pVoxel0px1ny1pz + weights[0][2][1] * pVoxel0px1py1nz +
                    weights[1][2][1] * pVoxel0px1py0pz + weights[2][2][1] *
                    pVoxel0px1py1pz - weights[0][0][2] * pVoxel1px1ny1nz -
                    weights[1][0][2] * pVoxel1px1ny0pz - weights[2][0][2] *
                    pVoxel1px1ny1pz + weights[0][2][2] * pVoxel1px1py1nz +
                    weights[1][2][2] * pVoxel1px1py0pz + weights[2][2][2] *
                    pVoxel1px1py1pz);

                const float zGrad(- weights[0][0][0] * pVoxel1nx1ny1nz +
                    weights[2][0][0] * pVoxel1nx1ny1pz - weights[0][1][0] *
                    pVoxel1nx0py1nz + weights[2][1][0] * pVoxel1nx0py1pz -
                    weights[0][2][0] * pVoxel1nx1py1nz + weights[2][2][0] *
                    pVoxel1nx1py1pz - weights[0][0][1] * pVoxel0px1ny1nz +
                    weights[2][0][1] * pVoxel0px1ny1pz - weights[0][1][1] *
                    pVoxel0px0py1nz + weights[2][1][1] * pVoxel0px0py1pz -
                    weights[0][2][1] * pVoxel0px1py1nz + weights[2][2][1] *
                    pVoxel0px1py1pz - weights[0][0][2] * pVoxel1px1ny1nz +
                    weights[2][0][2] * pVoxel1px1ny1pz - weights[0][1][2] *
                    pVoxel1px0py1nz + weights[2][1][2] * pVoxel1px0py1pz -
                    weights[0][2][2] * pVoxel1px1py1nz + weights[2][2][2] *
                    pVoxel1px1py1pz);

                //Note: The above actually give gradients going from low density to high density.
                //For our normals we want the the other way around, so we switch the components as we return them.
                return Vector3DFloat(-xGrad,-yGrad,-zGrad);
        }
        // End of compiler bug workaroumd.

        //Use the cell bitmasks to generate all the indices needed for that slice
        void generateIndicesForSlice(const Array2DUint8& pPreviousBitmask,
            const Array2DInt32& m_pPreviousVertexIndicesX,
            const Array2DInt32& m_pPreviousVertexIndicesY,
            const Array2DInt32& m_pPreviousVertexIndicesZ,
            const Array2DInt32& m_pCurrentVertexIndicesX,
            const Array2DInt32& m_pCurrentVertexIndicesY);

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

        //Holds a position in volume space.
        int32_t iXVolSpace;
        int32_t iYVolSpace;
        int32_t iZVolSpace;

        //Holds a position in region space.
        uint32_t uXRegSpace;
        uint32_t uYRegSpace;
        uint32_t uZRegSpace;

        //Used to return the number of cells in a slice which contain triangles.
        uint32_t m_uNoOfOccupiedCells;

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

        //Information about the region we are currently processing
        Region m_regSizeInVoxels;
        Region m_regSizeInCells;
        /*Region m_regSizeInVoxelsCropped;
        Region m_regSizeInVoxelsUncropped;
        Region m_regVolumeCropped;*/
        Region m_regSlicePrevious;
        Region m_regSliceCurrent;
    };
}

#include "PolyVoxCore/SurfaceExtractor.inl"

#endif