SLCompactGrid.h

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/**
 * \file      SLCompactGrid.h
 * \authors   Manuel Frischknecht, Marcus Hudritsch
 * \date      July 2015
 * \authors   Manuel Frischknecht, Marcus Hudritsch
 * \copyright http://opensource.org/licenses/GPL-3.0
*/
 
#ifndef SL_COMPACTGRID
#define SL_COMPACTGRID
 
#include <array>
#include <atomic>
#include <numeric>
#include <vector>
 
#include <SLAccelStruct.h>
#include <SLGLVertexArrayExt.h>
#include <SLVec3.h>
 
//-----------------------------------------------------------------------------
typedef std::function<void(const SLuint, const SLuint)> triVoxCallback;
//-----------------------------------------------------------------------------
//! Class for compact uniform grid acceleration structure
/*! This class implements the data structure proposed by Lagae & Dutre in their
paper "Compact, Fast and Robust Grids for Ray Tracing". It reduces the memory
footprint to 20% of a regular uniform grid implemented in SLUniformGrid.
*/
class SLCompactGrid : public SLAccelStruct
{
public:
    using Triangle = std::array<SLVec3f, 3>;
 
    SLCompactGrid(SLMesh* m);
    ~SLCompactGrid() { ; }
 
    void   build(SLVec3f minV, SLVec3f maxV);
    void   updateStats(SLNodeStats& stats);
    void   draw(SLSceneView* sv);
    SLbool intersect(SLRay* ray, SLNode* node);
 
    void deleteAll();
    void disposeBuffers()
    {
        if (_vao.vaoID())
            _vao.clearAttribs();
    }
 
    SLuint indexAtPos(const SLVec3i& p) const
    {
        return (SLuint)p.x + (SLuint)p.y * _size.x +
               (SLuint)p.z * _size.x * _size.y;
    }
    SLVec3f voxelCenter(const SLVec3i& pos) const;
    SLVec3i containingVoxel(const SLVec3f& p) const;
    void    getMinMaxVoxel(const Triangle& triangle,
                           SLVec3i&        minCell,
                           SLVec3i&        maxCell);
    void    ifTriangleInVoxelDo(triVoxCallback cb);
 
private:
    SLVec3ui           _size;              //!< num. of voxel in grid dir.
    SLuint             _numTriangles;      //!< NO. of triangles in the mesh
    SLVec3f            _voxelSize;         //!< size of a voxel
    SLVec3f            _voxelSizeHalf;     //!< half size of a voxel
    SLVuint            _voxelOffsets;      //!< Offset array (C in the paper)
    SLVushort          _triangleIndexes16; //!< 16 bit triangle index array (L in the paper)
    SLVuint            _triangleIndexes32; //!< 32 bit triangle index array (L in the paper)
    SLGLVertexArrayExt _vao;               //!< Vertex array object for rendering
};
//-----------------------------------------------------------------------------
#endif // SL_COMPACTGRID