source: GTP/trunk/App/Demos/Vis/FriendlyCulling/src/BvhConstructor.h @ 3280

#ifndef __BVHCONSTRUCTOR_H
#define __BVHCONSTRUCTOR_H

#include "Bvh.h"



namespace CHCDemoEngine
{

/** This class represents a bvh construction algorithm
*/
class BvhConstructor
{
public:

        BvhConstructor(SceneEntity **entities, int first, int last);

        /** Constructs a bvh and returns the root and the number of bvh nodes.
        */
        BvhNode *Construct(int &nodes);

        /** Types of split heuristics.
        */      
        enum {SPATIAL_MEDIAN, OBJECT_MEDIAN, SAH, SAH_OR_SIZE}; 

protected:

        //////////
        //-- sorting functions

        /** The method of subdividing objects into halves in some axis using spatial median
        */
        int     SortTrianglesSpatialMedian(BvhLeaf *leaf, int axis);
        /** The method of subdividing objects into halves in some axis
                using object median.
        */
        int SortTrianglesObjectMedian(BvhLeaf *leaf, int axis, float &pos);
        /** sort triangles along the axis with respect to the splitting plane 
                given by axis/position return index of the first tiangles belong 
                to the front of the splitting plane.
        */
        int     SortTriangles(BvhLeaf *leaf, const int axis, const float position);
        /** sort triangles by their area.
        */
        int SortTrianglesSurfaceArea(BvhLeaf *leaf, float sa);
        /** This function drives the subdivision.
        */
        BvhNode *SubdivideLeaf(BvhLeaf *leaf, int parentAxis);

        inline bool TerminationCriteriaMet(BvhLeaf *leaf) const;
        /** Update the bounding box of this node and the child nodes
        */
        void UpdateBoundingBoxes(BvhNode *node);
        /** Select splitting plane using SAH - returns the position of the splitting plane.
        */
        float SelectPlaneSah(BvhLeaf *leaf, int &axis, float &minCost);
        /** evaluate the SAH cost of a particulkar splitting plane
        */
        float EvaluateSahCost(BvhLeaf *leaf, int axis, float position);

        int CountTriangles(BvhNode *node) const;



        /////////////////

        SceneEntity **mEntities;

        int mFirst;
        int mLast;

        int mMaxDepth;
        int mMaxObjects;
        int mNumNodes;
        int mSplitType;
        int mMaxTriangles;
};

}

#endif // __BVH_H