#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};	

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