source: GTP/trunk/Lib/Vis/Preprocessing/src/VspOspTree.h @ 1184

#ifndef _VspOspTree_H__
#define _VspOspTree_H__

#include <stack>

#include "Mesh.h"
#include "Containers.h"
#include "Statistics.h"
#include "VssRay.h"
#include "RayInfo.h"
#include "gzstream.h"
#include "FlexibleHeap.h"


namespace GtpVisibilityPreprocessor {

class ViewCellLeaf;
//class VspViewCell;
class Plane3;
class AxisAlignedBox3;
class Ray;
class ViewCellsStatistics;
class ViewCellsManager;
class MergeCandidate;
class Beam;
class ViewCellsTree;
class Environment;
class VspInterior;
class VspLeaf;
class VspNode;
class KdNode;
class KdInterior;
class KdLeaf;
class OspTree;
class KdIntersectable;
class KdTree;
class VspTree;
class KdTreeStatistics;



template <typename T> class GtPriority
{
public:
        bool operator() (const T c1, const T c2) const
        {
                //return false;
                return c1->GetPriority() < c2->GetPriority();
        }
};


/** Candidate for a view space / object space split.
*/
class SplitCandidate: public Heapable
{  
public:

        enum {OBJECT_SPACE, VIEW_SPACE};

        /// the current split plane
        AxisAlignedPlane mSplitPlane;
        /// split axis of this plane (0, 1, 2, or 3 if non-axis-aligned)
        int mSplitAxis;
        /// the number of misses of max cost ratio until this split
        int mMaxCostMisses;

        SplitCandidate(): mRenderCostDecrease(0)
        {};

        SplitCandidate(const AxisAlignedPlane &plane): mSplitPlane(plane), mRenderCostDecrease(0)
        {}

        virtual void EvalPriority() = 0;
        virtual int Type() const = 0;
        virtual bool GlobalTerminationCriteriaMet() const = 0;

        /** Set render cost decrease achieved through this split.
        */
        void SetRenderCostDecrease(const float renderCostDecr)
        {
                mRenderCostDecrease = renderCostDecr;
        }
        
        float GetRenderCostDecrease() const
        {
                return mRenderCostDecrease;
        }

protected:

        /// render cost decrease achieved through this split
        float mRenderCostDecrease;
        
};


/** View space partition statistics.
*/
class VspTreeStatistics: public StatisticsBase
{
public:
        // total number of nodes
        int nodes;
        // number of splits
        int splits[3];
        
        // totals number of rays
        int rays;
        // maximal reached depth
        int maxDepth;
        // minimal depth
        int minDepth;
        
        // max depth nodes
        int maxDepthNodes;
        // minimum depth nodes
        int minDepthNodes;
        // max depth nodes
        int minPvsNodes;
        // nodes with minimum PVS
        int minRaysNodes;
        // max ray contribution nodes
        int maxRayContribNodes;
        // minimum area nodes
        int minProbabilityNodes;
        /// nodes termination because of max cost ratio;
        int maxCostNodes;
        // max number of rays per node
        int maxObjectRefs;
        /// samples contributing to pvs
        int contributingSamples;
        /// sample contributions to pvs
        int sampleContributions;
        /// largest pvs
        int maxPvs;
        /// number of invalid leaves
        int invalidLeaves;
        /// accumulated number of rays refs
        int accumRays;
        int pvs;
        // accumulated depth (used to compute average)
        int accumDepth;

        // Constructor
        VspTreeStatistics() 
        {
                Reset();
        }

        int Nodes() const {return nodes;}
        int Interior() const { return nodes / 2; }
        int Leaves() const { return (nodes / 2) + 1; }
        
        // TODO: computation wrong
        double AvgDepth() const { return accumDepth / (double)Leaves();}; 
        double AvgRays() const { return accumRays / (double)Leaves();}; 

        void Reset() 
        {
                nodes = 0;
                for (int i = 0; i < 3; ++ i)
                        splits[i] = 0;
                
                maxDepth = 0;
                minDepth = 99999;
                accumDepth = 0;
        pvs = 0;
                maxDepthNodes = 0;
                minPvsNodes = 0;
                minRaysNodes = 0;
                maxRayContribNodes = 0;
                minProbabilityNodes = 0;
                maxCostNodes = 0;

                contributingSamples = 0;
                sampleContributions = 0;

                maxPvs = 0;
                invalidLeaves = 0;
                accumRays = 0;
                maxObjectRefs = 0;
        }

        void Print(ostream &app) const;

        friend ostream &operator<<(ostream &s, const VspTreeStatistics &stat) 
        {
                stat.Print(s);
                return s;
        } 
};


/** View space partition statistics.
*/
class OspTreeStatistics: public StatisticsBase
{
public:
        // total number of nodes
        int nodes;
        // number of splits
        int splits[3];
        
        // maximal reached depth
        int maxDepth;
        // minimal depth
        int minDepth;
        
        // max depth nodes
        int maxDepthNodes;
        // minimum depth nodes
        int minDepthNodes;
        // max depth nodes
        int minPvsNodes;
        // minimum area nodes
        int minProbabilityNodes;
        /// nodes termination because of max cost ratio;
        int maxCostNodes;
        // max number of objects per node
        int maxObjectRefs;
        int objectRefs;
        /// samples contributing to pvs
        int contributingSamples;
        /// sample contributions to pvs
        int sampleContributions;
        /// largest pvs
        int maxPvs;
        /// number of invalid leaves
        int invalidLeaves;
        /// accumulated number of rays refs
        int accumRays;
        /// potentially visible objects from this leaf
        int pvs;

        // accumulated depth (used to compute average)
        int accumDepth;

        // Constructor
        OspTreeStatistics() 
        {
                Reset();
        }

        int Nodes() const {return nodes;}
        int Interior() const { return nodes / 2; }
        int Leaves() const { return (nodes / 2) + 1; }
        
        // TODO: computation wrong
        double AvgDepth() const { return accumDepth / (double)Leaves();}; 
        

        void Reset() 
        {
                nodes = 0;
                for (int i = 0; i < 3; ++ i)
                        splits[i] = 0;
                
                maxDepth = 0;
                minDepth = 99999;
                accumDepth = 0;
        pvs = 0;
                maxDepthNodes = 0;
                minPvsNodes = 0;
        
                minProbabilityNodes = 0;
                maxCostNodes = 0;

                contributingSamples = 0;
                sampleContributions = 0;

                maxPvs = 0;
                invalidLeaves = 0;
                objectRefs = 0;

                maxObjectRefs = 0;
        }


        void Print(ostream &app) const;

        friend ostream &operator<<(ostream &s, const OspTreeStatistics &stat) 
        {
                stat.Print(s);
                return s;
        } 
};


/**
    VspNode abstract class serving for interior and leaf node implementation
*/
class VspNode
{
public:
        
        // types of vsp nodes
        enum {Interior, Leaf};

        VspNode();
        virtual ~VspNode(){};
        VspNode(VspInterior *parent);

        /** Determines whether this node is a leaf or not
                @return true if leaf
        */
        virtual bool IsLeaf() const = 0;

        virtual int Type() const = 0;

        /** Determines whether this node is a root
                @return true if root
        */
        virtual bool IsRoot() const;

        /** Returns parent node.
        */
        VspInterior *GetParent();

        /** Sets parent node.
        */
        void SetParent(VspInterior *parent);

        /** Returns true if this node is a sibling of node n.
        */
        bool IsSibling(VspNode *n) const;

        /** returns depth of the node.
        */
        int GetDepth() const;

        /** returns true if the whole subtree is valid
        */
        bool TreeValid() const;

        void SetTreeValid(const bool v);

        //-- mailing options

        void Mail() { mMailbox = sMailId; }
        static void NewMail() { ++ sMailId; }
        bool Mailed() const { return mMailbox == sMailId; }

        static int sMailId;
        int mMailbox;

        int mTimeStamp;

protected:

        /// if this sub tree is a completely valid view space region
        bool mTreeValid;
        /// parent of this node
        VspInterior *mParent;
};


/** BSP interior node implementation 
*/
class VspInterior: public VspNode 
{
public:
        /** Standard contructor taking split plane as argument.
        */
        VspInterior(const AxisAlignedPlane &plane);

        ~VspInterior();
        /** @return false since it is an interior node 
        */
        bool IsLeaf() const;

        int Type() const;

        VspNode *GetBack();
        VspNode *GetFront();

        /** Returns split plane.
        */
        AxisAlignedPlane GetPlane() const;

        /** Returns position of split plane.
        */
        float GetPosition() const;

        /** Returns split axis.
        */
        int GetAxis() const;

        /** Replace front or back child with new child.
        */
        void ReplaceChildLink(VspNode *oldChild, VspNode *newChild);

        /** Replace front and back child.
        */
        void SetupChildLinks(VspNode *front, VspNode *back);

        friend ostream &operator<<(ostream &s, const VspInterior &A)
        {
                return s << A.mPlane.mAxis << " " << A.mPlane.mPosition;
        }

        AxisAlignedBox3 GetBoundingBox() const;
        void SetBoundingBox(const AxisAlignedBox3 &box);

        /** Computes intersection of this plane with the ray segment.
        */
        int ComputeRayIntersection(const RayInfo &rayData, float &t) const
        {
                return rayData.ComputeRayIntersection(mPlane.mAxis, mPlane.mPosition, t);
        }


protected:

        AxisAlignedBox3 mBoundingBox;

        /// Splitting plane corresponding to this node
        AxisAlignedPlane mPlane;

        /// back node
        VspNode *mBack;
        /// front node
        VspNode *mFront;
};


/** BSP leaf node implementation.
*/
class VspLeaf: public VspNode 
{
        friend VspTree;

public:
        VspLeaf();
        VspLeaf(ViewCellLeaf *viewCell);
        VspLeaf(VspInterior *parent);
        VspLeaf(VspInterior *parent, ViewCellLeaf *viewCell);

        ~VspLeaf();

        /** @return true since it is an interior node 
        */
        bool IsLeaf() const;
        
        int Type() const;

        /** Returns pointer of view cell.
        */
        ViewCellLeaf *GetViewCell() const;

        /** Sets pointer to view cell.
        */
        void SetViewCell(ViewCellLeaf *viewCell);

        SplitCandidate *GetSplitCandidate() const 
        { 
                return mSplitCandidate; 
        }

public:

        /// Rays piercing this leaf.
        VssRayContainer mVssRays;
        
        /// leaf pvs
        ObjectPvs *mPvs;

        /// Probability that the view point lies in this leaf
        float mProbability;

protected:

        /// pointer to a split plane candidate splitting this leaf
        SplitCandidate *mSplitCandidate;

        /// if NULL this does not correspond to feasible viewcell
        ViewCellLeaf *mViewCell;
};


#if 0
typedef std::priority_queue<SplitCandidate *, 
                                                        std::vector<SplitCandidate *>, 
                                                        GtPriority<std::vector<SplitCandidate *>::value_type> > SplitQueue;
#endif

typedef map<KdNode *, KdIntersectable *> KdIntersectableMap;

typedef FlexibleHeap<SplitCandidate *> SplitQueue;

/** View Space Partitioning tree.
*/
class VspTree 
{
        friend class ViewCellsParseHandlers;
        friend class HierarchyManager;

public:
        
        /** Additional data which is passed down the BSP tree during traversal.
        */
        class VspTraversalData
        {  
        public:
                /// the current node
                VspLeaf *mNode;
                /// current depth
                int mDepth;
                /// rays piercing this node
                RayInfoContainer *mRays;
                /// the probability that this node contains view point
                float mProbability;
                /// the bounding box of the node
                AxisAlignedBox3 mBoundingBox;
                /// pvs size
                int mPvs;
                /// how often this branch has missed the max-cost ratio
                int mMaxCostMisses;
                // current priority
                float mPriority;

                
                /** Returns average ray contribution.
                */
                float GetAvgRayContribution() const
                {
                        return (float)mPvs / ((float)mRays->size() + Limits::Small);
                }


                VspTraversalData():
                mNode(NULL),
                mDepth(0),
                mRays(NULL),
                mPvs(0),
                mProbability(0.0),
                mMaxCostMisses(0), 
                mPriority(0)
                {}
                
                VspTraversalData(VspLeaf *node, 
                                                 const int depth, 
                                                 RayInfoContainer *rays,
                                                 const int pvs,
                                                 const float p,
                                                 const AxisAlignedBox3 &box):
                mNode(node), 
                mDepth(depth), 
                mRays(rays),
                mPvs(pvs),
                mProbability(p),
                mBoundingBox(box),
                mMaxCostMisses(0),
                mPriority(0)
                {}

                VspTraversalData(const int depth, 
                                                 RayInfoContainer *rays,
                                                 const AxisAlignedBox3 &box): 
                mNode(NULL), 
                mDepth(depth), 
                mRays(rays),
                mPvs(0),
                mProbability(0),
                mMaxCostMisses(0),
                mBoundingBox(box)
                {}

                /** Returns cost of the traversal data.
                */
                float GetCost() const
                {
                        //cout << mPriority << endl;
                        return mPriority;
                }

                /// deletes contents and sets them to NULL
                void Clear()
                {
                        DEL_PTR(mRays);
                }

                friend bool operator<(const VspTraversalData &a, const VspTraversalData &b)
                {
                        return a.GetCost() < b.GetCost();
                }
    };

        /** Candidate for a view space split.
        */
        class VspSplitCandidate: public SplitCandidate
        {  
        public:

                static VspTree* sVspTree;

                /// parent node traversal data
                VspTraversalData mParentData;
                
                VspSplitCandidate(const VspTraversalData &tData): mParentData(tData)
                {};

                int Type() const { return VIEW_SPACE; }

                void EvalPriority()
                {
                        sVspTree->EvalSplitCandidate(*this);    
                }

                bool GlobalTerminationCriteriaMet() const
                {
                        return sVspTree->GlobalTerminationCriteriaMet(mParentData);
                }

                VspSplitCandidate(const AxisAlignedPlane &plane, const VspTraversalData &tData): 
                SplitCandidate(plane), mParentData(tData)
                {}
        };

        /** Struct for traversing line segment.
        */
        struct LineTraversalData 
        {
                VspNode *mNode;
                Vector3 mExitPoint;
                
                float mMaxT;
    
                LineTraversalData () {}
                LineTraversalData (VspNode *n, const Vector3 &p, const float maxt):
                mNode(n), mExitPoint(p), mMaxT(maxt) {}
        };

        //typedef std::priority_queue<VspTraversalData> VspOspTraversalQueue;

        /** Default constructor creating an empty tree.
        */ 
        VspTree();

        /** Default destructor.
        */
        ~VspTree();

        /** Returns BSP Tree statistics.
        */
        const VspTreeStatistics &GetStatistics() const; 
  
        /** Returns bounding box of the specified node.
        */
        AxisAlignedBox3 GetBoundingBox(VspNode *node) const;

        /** Returns list of BSP leaves with pvs smaller than
                a certain threshold.
                @param onlyUnmailed if only the unmailed leaves should be considered
                @param maxPvs the maximal pvs of a leaf to be added (-1 means unlimited)
        */
        void CollectLeaves(vector<VspLeaf *> &leaves, 
                                           const bool onlyUnmailed = false,
                                           const int maxPvs = -1) const;

        /** Returns box which bounds the whole tree.
        */
        AxisAlignedBox3 GetBoundingBox() const;

        /** Returns root of the view space partitioning tree.
        */
        VspNode *GetRoot() const;

        /** Collects the leaf view cells of the tree
                @param viewCells returns the view cells 
        */
        void CollectViewCells(ViewCellContainer &viewCells, bool onlyValid) const;

        /** A ray is cast possible intersecting the tree.
                @param the ray that is cast.
                @returns the number of intersections with objects stored in the tree.
        */
        int CastRay(Ray &ray);


        /** finds neighbouring leaves of this tree node.
        */
        int FindNeighbors(VspLeaf *n, 
                                          vector<VspLeaf *> &neighbors, 
                                          const bool onlyUnmailed) const;

        /** Returns random leaf of BSP tree.
                @param halfspace defines the halfspace from which the leaf is taken.
        */
        VspLeaf *GetRandomLeaf(const Plane3 &halfspace);

        /** Returns random leaf of BSP tree.
                @param onlyUnmailed if only unmailed leaves should be returned.
        */
        VspLeaf *GetRandomLeaf(const bool onlyUnmailed = false);

        /** Returns epsilon of this tree.
        */
        float GetEpsilon() const;

        /** Casts line segment into the tree.
                @param origin the origin of the line segment
                @param termination the end point of the line segment
                @returns view cells intersecting the line segment.
        */
    int CastLineSegment(const Vector3 &origin,
                                                const Vector3 &termination,
                                                ViewCellContainer &viewcells);

                
        /** Sets pointer to view cells manager.
        */
        void SetViewCellsManager(ViewCellsManager *vcm);

        /** Returns view cell the current point is located in.
                @param point the current view point
                @param active if currently active view cells should be returned or
                elementary view cell
        */
        ViewCell *GetViewCell(const Vector3 &point, const bool active = false);


        /** Returns true if this view point is in a valid view space,
                false otherwise.
        */
        bool ViewPointValid(const Vector3 &viewPoint) const;

        /** Returns view cell corresponding to 
                the invalid view space.
        */
        VspViewCell *GetOutOfBoundsCell();

        /** Writes tree to output stream
        */
#if ZIPPED_VIEWCELLS
        bool Export(ogzstream &stream);
#else
        bool Export(ofstream &stream);
#endif

        /** Casts beam, i.e. a 5D frustum of rays, into tree.
                Tests conservative using the bounding box of the nodes.
                @returns number of view cells it intersected
        */
        int CastBeam(Beam &beam);


        /** Checks if tree validity-flags are right 
                with respect to view cell valitiy.
                If not, marks subtree as invalid.
        */
        void ValidateTree();

        /** Invalid view cells are added to the unbounded space
        */
        void CollapseViewCells();

        /** Collects rays stored in the leaves.
        */
        void CollectRays(VssRayContainer &rays);

        /** Intersects box with the tree and returns the number of intersected boxes.
                @returns number of view cells found
        */
        int ComputeBoxIntersections(const AxisAlignedBox3 &box, 
                                                                ViewCellContainer &viewCells) const;

        /** Remove the references of the parent view cell from the kd nodes associated with
                the objects.
        */
        void RemoveParentViewCellReferences(ViewCell *parent) const;

        /** Adds references to the view cell to the kd nodes associated with the objects.
        */
        void AddViewCellReferences(ViewCell *vc) const;

        /** Returns view cells of this ray, either taking precomputed cells
                or by recomputation.
        */
        void GetViewCells(const VssRay &ray, ViewCellContainer &viewCells);


        ViewCellsTree *GetViewCellsTree() const { return mViewCellsTree; }

        void SetViewCellsTree(ViewCellsTree *vt) { mViewCellsTree = vt; }


protected:

        // --------------------------------------------------------------
        // For sorting objects
        // --------------------------------------------------------------
        struct SortableEntry
        {
                enum EType 
                {
                        ERayMin,
                        ERayMax
                };

                int type;
                float value;
                VssRay *ray;
  
                SortableEntry() {}
                SortableEntry(const int t, const float v, VssRay *r): 
                type(t), value(v), ray(r) 
                {
                }
                
                friend bool operator<(const SortableEntry &a, const SortableEntry &b)
                {
                        return a.value < b.value;
                }
        };

        /** faster evaluation of split plane cost for kd axis aligned cells.
        */
        float EvalLocalSplitCost(const VspTraversalData &data,
                                                         const AxisAlignedBox3 &box,
                                                         const int axis,
                                                         const float &position,
                                                         float &pFront,
                                                         float &pBack) const;

        void ComputeBoundingBox(const VssRayContainer &rays,
                                                        AxisAlignedBox3 *forcedBoundingBox);

        /** Evaluates candidate for splitting.
        */
        void EvalSplitCandidate(VspSplitCandidate &splitData);

        /** Evaluates render cost decrease of next split.
        */
        float EvalRenderCostDecrease(const AxisAlignedPlane &candidatePlane,
                                                                 const VspTraversalData &data,
                                                                 float &normalizedOldRenderCost) const;

        /** Collects view cells in the subtree under root.
        */
        void CollectViewCells(VspNode *root, 
                                                  bool onlyValid, 
                                                  ViewCellContainer &viewCells,
                                                  bool onlyUnmailed = false) const;

        /** Returns view cell corresponding to 
                the invalid view space. If it does not exist, it is created.
        */
        VspViewCell *GetOrCreateOutOfBoundsCell();

        /** Collapses the tree with respect to the view cell partition,
                i.e. leaves having the same view cell are collapsed.
                @param node the root of the subtree to be collapsed
                @param collapsed returns the number of collapsed nodes
                @returns node of type leaf if the node could be collapsed, 
                this node otherwise
        */
        VspNode *CollapseTree(VspNode *node, int &collapsed);

        /** Helper function revalidating the view cell leaf list after merge.
        */
        void RepairViewCellsLeafLists();

        /** Evaluates tree stats in the BSP tree leafs.
        */
        void EvaluateLeafStats(const VspTraversalData &data);

        /** Subdivides node using a best split priority queue.
            @param tQueue the best split priority queue
                @param splitCandidate the candidate for the next split
                @param globalCriteriaMet if the global termination criteria were already met
                @returns new root of the subtree
        */
        VspNode *Subdivide(SplitQueue &tQueue,
                                           SplitCandidate *splitCandidate,
                                           const bool globalCriteriaMet);

        /** Adds stats to subdivision log file.
        */
        void AddSubdivisionStats(const int viewCells,
                                                         const float renderCostDecr,
                                                         const float totalRenderCost,
                                                         const float avgRenderCost);
        
        /** Subdivides leaf.
                        
                @param tData data object holding, e.g., a pointer to the leaf
                @param frontData returns the data (e.g.,  pointer to the leaf) in front of the split plane
                @param backData returns the data (e.g.,  pointer to the leaf) in the back of the split plane
                
                @param rays the polygons to be filtered
                @param frontRays returns the polygons in front of the split plane
        
                @returns the root of the subdivision
        */
        VspInterior *SubdivideNode(const AxisAlignedPlane &splitPlane,
                                                           VspTraversalData &tData,
                                                           VspTraversalData &frontData,
                               VspTraversalData &backData);

        /** Selects an axis aligned for the next split.
                @returns cost for this split
        */
        float SelectSplitPlane(const VspTraversalData &tData,
                                                   AxisAlignedPlane &plane,
                                                   float &pFront,
                                                   float &pBack);

        /** Sorts split candidates along the specified axis.
                The split candidates are generated on possible visibility
                events (i.e., where ray segments intersect the ray boundaries).
                The sorted candidates are needed to compute the heuristics.

                @param polys the input for choosing split candidates
                @param axis the current split axis
                @param splitCandidates returns sorted list of split candidates
        */
        void SortSplitCandidates(const RayInfoContainer &rays, 
                                                         const int axis, 
                                                         float minBand, 
                                                         float maxBand);

        /** Evaluate pvs size associated with the rays.
        */
        int EvalPvsSize(const RayInfoContainer &rays) const;

        /** Computes pvs increase with respect to the previous pvs for heuristics.
        */
        int GetPvsIncr(Intersectable *object, const KdPvsMap &activeNodes);

        /** Returns absolute pvs contribution of this object.
        */
        int GetPvsContribution(Intersectable *object) const;

        /** Computes best cost for axis aligned planes.
        */
        float EvalLocalCostHeuristics(const VspTraversalData &tData,
                                                                  const AxisAlignedBox3 &box,
                                                                  const int axis,
                                                                  float &position);

        /** Evaluates the influence on the pvs of the visibility event ve.
                @param ve the visibility event
                @param pvsLeft updates the left pvs
                @param rightPvs updates the right pvs
        */
        void EvalPvsIncr(const SortableEntry &ve,
                                          int &pvsLeft,
                                          int &pvsRight) const;

        void RemoveContriFromPvs(KdLeaf *leaf, int &pvs) const;
        void AddContriToPvs(KdLeaf *leaf, int &pvs) const;

        /** Prepares objects for the heuristics.
                @returns pvs size of the ray container
        */
        int PrepareHeuristics(const RayInfoContainer &rays);

        int PrepareHeuristics(KdLeaf *leaf);

        /** Subdivides the rays into front and back rays according to the split plane.
                
                @param plane the split plane
                @param rays contains the rays to be split. The rays are 
                           distributed into front and back rays.
                @param frontRays returns rays on the front side of the plane
                @param backRays returns rays on the back side of the plane
                
                @returns the number of splits
        */
        int SplitRays(const AxisAlignedPlane &plane,
                                  RayInfoContainer &rays, 
                              RayInfoContainer &frontRays, 
                                  RayInfoContainer &backRays) const;

        /** Classfifies the object with respect to the 
                pvs of the front and back leaf and updates pvs size
                accordingly.

                @param obj the object to be added
                @param cf the ray classification regarding the split plane
                @param frontPvs returns the PVS of the front partition
                @param backPvs returns the PVS of the back partition
        
        */
        void UpdateObjPvsContri(Intersectable *obj, 
                                         const int cf, 
                                         float &frontPvs, 
                                         float &backPvs, 
                                         float &totalPvs) const;
        
        /** See UpdateObjPvsContri. 
        */
        void UpdateKdLeafPvsContri(KdLeaf *leaf,
                const int cf,
                float &frontPvs,
                float &backPvs,
                float &totalPvs) const;

        /** Collects pvs from rays.
        */
        void CollectPvs(const RayInfoContainer &rays,
                                        ObjectContainer &objects) const;

        /** Returns true if tree can be terminated.
        */
        inline bool LocalTerminationCriteriaMet(const VspTraversalData &data) const;

        /** Returns true if global tree can be terminated.
        */
        inline bool GlobalTerminationCriteriaMet(const VspTraversalData &data) const;

        /** Adds ray sample contributions to the PVS.
                @param sampleContributions the number contributions of the samples
                @param contributingSampels the number of contributing rays
                
        */
        void AddSamplesToPvs(VspLeaf *leaf,
                                                 const RayInfoContainer &rays, 
                                                 float &sampleContributions,
                                                 int &contributingSamples);

        bool AddKdLeafToPvs(KdLeaf *leaf, 
                                                ViewCell *vc, 
                                                const float pvs, 
                                                float &contribution);

        /** Propagates valid flag up the tree.
        */
        void PropagateUpValidity(VspNode *node);

        /** Writes the node to disk
                @note: should be implemented as visitor.
        */
#if ZIPPED_VIEWCELLS
        void ExportNode(VspNode *node, ogzstream &stream);
#else
        void ExportNode(VspNode *node, ofstream &stream);
#endif

        /** Returns estimated memory usage of tree.
        */
        float GetMemUsage() const;

        /** Updates view cell pvs of objects.
        */
        void ProcessViewCellObjects(ViewCell *parent, 
                ViewCell *front, 
                ViewCell *back) const;

        void CreateViewCell(VspTraversalData &tData, const bool updatePvs);

        /** Collect split candidates which are affected by the last split
                and must be reevaluated.
        */
        void CollectDirtyCandidates(VspSplitCandidate *sc, vector<SplitCandidate *> &dirtyList);

        /** Rays will be clipped to the bounding box.
        */
        void PreprocessRays(const VssRayContainer &sampleRays, RayInfoContainer &rays);

        /** Evaluate subdivision statistics.
        */
        void EvalSubdivisionStats(const SplitCandidate &tData);



protected:


        /// pointer to the hierarchy of view cells
        ViewCellsTree *mViewCellsTree;

        OspTree *mOspTree;

        bool mUseKdPvsForHeuristics;
        bool mStoreKdPvs;

        ViewCellsManager *mViewCellsManager;
        
        vector<SortableEntry> *mLocalSplitCandidates;

        /// Pointer to the root of the tree
        VspNode *mRoot;
                
        VspTreeStatistics mVspStats;
        
        /// View cell corresponding to the space outside the valid view space
        VspViewCell *mOutOfBoundsCell;

        /// box around the whole view domain
        AxisAlignedBox3 mBoundingBox;


        //-- local termination

        /// minimal number of rays before subdivision termination
        int mTermMinRays;
        /// maximal possible depth
        int mTermMaxDepth;
        /// mininum probability
        float mTermMinProbability;
        /// mininum PVS
        int mTermMinPvs;
        /// maximal contribution per ray
        float mTermMaxRayContribution;
        /// maximal acceptable cost ratio
        float mTermMaxCostRatio;
        /// tolerance value indicating how often the max cost ratio can be failed
        int mTermMissTolerance;


        //-- global criteria
        float mTermMinGlobalCostRatio;
        int mTermGlobalCostMissTolerance;
        int mGlobalCostMisses;

        /// maximal number of view cells
        int mMaxViewCells;
        /// maximal tree memory
        float mMaxMemory;
        /// the tree is out of memory
        bool mOutOfMemory;



        //-- split heuristics based parameters
        
        bool mUseCostHeuristics;
        /// balancing factor for PVS criterium
        float mCtDivCi; 
        /// if only driving axis should be used for split
        bool mOnlyDrivingAxis;
        /// if random split axis should be used
        bool mUseRandomAxis;
        /// if vsp bsp tree should simulate octree
        bool mCirculatingAxis;
        /// minimal relative position where the split axis can be placed
        float mMinBand;
        /// maximal relative position where the split axis can be placed
        float mMaxBand;


        /// current time stamp (used for keeping split history)
        int mTimeStamp;
        // if rays should be stored in leaves
        bool mStoreRays;

        /// epsilon for geometric comparisons
        float mEpsilon;


        /// subdivision stats output file
        ofstream  mSubdivisionStats;
        /// keeps track of cost during subdivision
        float mTotalCost;
        /// keeps track of overall pvs size during subdivision
        int mTotalPvsSize;
        /// number of currenly generated view cells
        int mCreatedViewCells;

        /// weight between render cost decrease and node render cost
        float mRenderCostDecreaseWeight;

        int mMaxTests;
};


/** View Space Partitioning tree.
*/
class OspTree 
{
        friend class ViewCellsParseHandlers;
        friend class HierarchyManager;

public:
        
        /** Additional data which is passed down the BSP tree during traversal.
        */
        class OspTraversalData
        {  
        public:
                /// the current node
                KdLeaf *mNode;
                /// current depth
                int mDepth;
                /// rays piercing this node
                RayInfoContainer *mRays;
                /// the probability that this node contains view point
                float mProbability;
                /// the bounding box of the node
                AxisAlignedBox3 mBoundingBox;
                /// pvs size
                int mPvs;
                /// how often this branch has missed the max-cost ratio
                int mMaxCostMisses;
                // current axis
                int mAxis;
                // current priority
                float mPriority;


                OspTraversalData():
                mNode(NULL),
                mRays(NULL),
                mDepth(0),
                mPvs(0),
                mProbability(0.0),
                mMaxCostMisses(0), 
                mPriority(0),
                mAxis(0)
                {}
                
                OspTraversalData(KdLeaf *node, 
                                                 const int depth,
                         RayInfoContainer *rays,
                                                 const int pvs,
                                                 const float p,
                                                 const AxisAlignedBox3 &box):
                mNode(node), 
                mDepth(depth),
                mRays(rays),
                mPvs(pvs),
                mProbability(p),
                mBoundingBox(box),
                mMaxCostMisses(0),
                mPriority(0),
                mAxis(0)
                {}

                OspTraversalData(const int depth, 
                        RayInfoContainer *rays,
                        const AxisAlignedBox3 &box): 
                mNode(NULL), 
                mDepth(depth),
                mRays(rays),
                mPvs(0),
                mProbability(0),
                mMaxCostMisses(0),
                mAxis(0),
                mBoundingBox(box)
                {}

                /** Returns cost of the traversal data.
                */
                float GetCost() const
                {
                        //cout << mPriority << endl;
                        return mPriority;
                }

                /// deletes contents and sets them to NULL
                void Clear()
                {
                        DEL_PTR(mRays);
                }


                friend bool operator<(const OspTraversalData &a, const OspTraversalData &b)
                {
                        return a.GetCost() < b.GetCost();
                }
    };

        /** Candidate for a view space split.
        */
        class OspSplitCandidate: public SplitCandidate
        {  
        public:
                static OspTree* sOspTree;

                /// parent data
                OspTraversalData mParentData;
                
                OspSplitCandidate(const OspTraversalData &tData): mParentData(tData)
                {};

                int Type() const { return OBJECT_SPACE; }
        
                void EvalPriority()
                {
                        sOspTree->EvalSplitCandidate(*this);    
                }

                bool GlobalTerminationCriteriaMet() const
                {
                        return sOspTree->GlobalTerminationCriteriaMet(mParentData);
                }


                OspSplitCandidate(const AxisAlignedPlane &plane, const OspTraversalData &tData): 
                SplitCandidate(plane), mParentData(tData)
                {}
        };

        /** Struct for traversing line segment.
        */
        struct LineTraversalData 
        {
                KdNode *mNode;
                Vector3 mExitPoint;
                
                float mMaxT;
    
                LineTraversalData () {}
                LineTraversalData (KdNode *n, const Vector3 &p, const float maxt):
                mNode(n), mExitPoint(p), mMaxT(maxt) {}
        };

        //typedef std::priority_queue<VspTraversalData> VspOspTraversalQueue;

        /** Default constructor creating an empty tree.
        */ 
        OspTree();

        OspTree(const KdTree &kdTree);

        /** Default destructor.
        */
        ~OspTree();

        /** Returns tree statistics.
        */
        const OspTreeStatistics &GetStatistics() const; 
  
        /** Returns bounding box of the specified node.
        */
        AxisAlignedBox3 GetBoundingBox(KdNode *node) const;

        /** Returns list of leaves with pvs smaller than
                a certain threshold.
                @param onlyUnmailed if only the unmailed leaves should be considered
                @param maxPvs the maximal pvs of a leaf to be added (-1 means unlimited)
        */
        
        void CollectLeaves(vector<KdLeaf *> &leaves) const;


        /** Returns bounding box of the whole tree (= bbox of root node)
        */
        AxisAlignedBox3 GetBoundingBox()const;

        /** Returns root of the view space partitioning tree.
        */
        KdNode *GetRoot() const;

        /** Collects the leaf view cells of the tree
                @param viewCells returns the view cells 
        */
        void CollectViewCells(ViewCellContainer &viewCells, bool onlyValid) const;

        /** A ray is cast possible intersecting the tree.
                @param the ray that is cast.
                @returns the number of intersections with objects stored in the tree.
        */
        int CastRay(Ray &ray);

        /** finds neighbouring leaves of this tree node.
        */
        int FindNeighbors(KdLeaf *n, 
                                          vector<VspLeaf *> &neighbors, 
                                          const bool onlyUnmailed) const;

        /** Returns random leaf of BSP tree.
                @param halfspace defines the halfspace from which the leaf is taken.
        */
        KdLeaf *GetRandomLeaf(const Plane3 &halfspace);

        /** Returns random leaf of BSP tree.
                @param onlyUnmailed if only unmailed leaves should be returned.
        */
        KdLeaf *GetRandomLeaf(const bool onlyUnmailed = false);

        /** Returns epsilon of this tree.
        */
        float GetEpsilon() const;

        /** Casts line segment into the tree.
                @param origin the origin of the line segment
                @param termination the end point of the line segment
                @returns view cells intersecting the line segment.
        */
    int CastLineSegment(const Vector3 &origin,
                                                const Vector3 &termination,
                                                ViewCellContainer &viewcells);
                
        /** Sets pointer to view cells manager.
        */
        void SetViewCellsManager(ViewCellsManager *vcm);

        /** Writes tree to output stream
        */
#if ZIPPED_VIEWCELLS
        bool Export(ogzstream &stream);
#else
        bool Export(ofstream &stream);
#endif

        /** Returns or creates a new intersectable for use in a kd based pvs.
                The OspTree is responsible for destruction of the intersectable.
        */
        KdIntersectable *GetOrCreateKdIntersectable(KdNode *node);

        /** Collects rays stored in the leaves.
        */
        void CollectRays(VssRayContainer &rays);

        /** Intersects box with the tree and returns the number of intersected boxes.
                @returns number of view cells found
        */
        int ComputeBoxIntersections(const AxisAlignedBox3 &box, 
                                                                ViewCellContainer &viewCells) const;


        /** Returns kd leaf the point pt lies in, starting from root.
        */
        KdLeaf *GetLeaf(const Vector3 &pt, KdNode *root = NULL) const;


        ViewCellsTree *GetViewCellsTree() const { return mViewCellsTree; }

        void SetViewCellsTree(ViewCellsTree *vt) { mViewCellsTree = vt; }

        float EvalRenderCost();

protected:

        // --------------------------------------------------------------
        // For sorting objects
        // --------------------------------------------------------------
        struct SortableEntry
        {
                /** There is a 3th "event" for rays which intersect a
                        box in the middle. These "events" don't induce a change in
                        pvs size, but may induce a change in view cell volume.
                */
                enum EType 
                {
                        BOX_MIN,
                        BOX_MAX,
                        BOX_INTERSECT
                };

                int mType;
                //int mPvs;
                float mPos;
                VssRay *mRay;
                
                Intersectable *mObject;

                SortableEntry() {}

                SortableEntry(const int type,
                        //const float pvs, 
                        const float pos,
                        Intersectable *obj,
                        VssRay *ray):
                mType(type), 
                //mPvs(pvs), 
                mPos(pos), 
                mObject(obj),
                mRay(ray)
                {}

                bool operator<(const SortableEntry &b) const 
                {
                        return mPos < b.mPos;
                }
        };

 
        /** faster evaluation of split plane cost for kd axis aligned cells.
        */
        float EvalLocalSplitCost(const OspTraversalData &data,
                                                         const AxisAlignedBox3 &box,
                                                         const int axis,
                                                         const float &position,
                                                         float &pFront,
                                                         float &pBack) const;

        /** Evaluates candidate for splitting.
        */
        void EvalSplitCandidate(OspSplitCandidate &splitData);

        /** Computes priority of the traversal data and stores it in tData.
        */
        void EvalPriority(OspTraversalData &tData) const;

        /** Evaluates render cost decrease of next split.
        */
        float EvalRenderCostDecrease(const AxisAlignedPlane &candidatePlane,
                                                                 const OspTraversalData &data,
                                                                 float &normalizedOldRenderCost) const;


        /** Collects view cells in the subtree under root.
        */
        void CollectViewCells(KdNode *root, 
                                                  bool onlyValid, 
                                                  ViewCellContainer &viewCells,
                                                  bool onlyUnmailed = false) const;

        /** Evaluates tree stats in the BSP tree leafs.
        */
        void EvaluateLeafStats(const OspTraversalData &data);

        /** Subdivides node using a best split priority queue.
            @param tQueue the best split priority queue
                @param splitCandidate the candidate for the next split
                @param globalCriteriaMet if the global termination criteria were already met
                @returns new root of the subtree
        */
        KdNode *Subdivide(SplitQueue &tQueue,
                                          SplitCandidate *splitCandidate,
                                          const bool globalCriteriaMet);
        
        /** Subdivides leaf.
                @param leaf the leaf to be subdivided
                
                @param polys the polygons to be split
                @param frontPolys returns the polygons in front of the split plane
                @param backPolys returns the polygons in the back of the split plane
                
                @param rays the polygons to be filtered
                @param frontRays returns the polygons in front of the split plane
                @param backRays returns the polygons in the back of the split plane

                @returns the root of the subdivision
        */
        KdInterior *SubdivideNode(
                const AxisAlignedPlane &splitPlane,
                const OspTraversalData &tData,
                OspTraversalData &frontData,
                OspTraversalData &backData);

        void SplitObjects(KdLeaf *leaf,
                                          const AxisAlignedPlane & splitPlane,
                                          const ObjectContainer &objects,
                                          ObjectContainer &front,
                                          ObjectContainer &back);

        /** does some post processing on the objects in the new child leaves.
        */
        void ProcessMultipleRefs(KdLeaf *leaf) const;

        /** Selects an axis aligned for the next split.
                @returns cost for this split
        */
        float SelectPlane(const OspTraversalData &tData,
                                          AxisAlignedPlane &plane,
                                          float &pFront,
                                          float &pBack);

        /** Sorts split candidates for cost heuristics using axis aligned splits.
                @param node the current node
                @param axis the current split axis
        */
        void SortSplitCandidates(const OspTraversalData &data,
                                                         const int axis, 
                                                         float minBand, 
                                                         float maxBand);

        /** Computes best cost for axis aligned planes.
        */
        float EvalLocalCostHeuristics(const OspTraversalData &tData,
                const AxisAlignedBox3 &box,
                const int axis,
                float &position,
                int &objectsFront,
                int &objectsBack);

        /** Subdivides the rays into front and back rays according to the split plane.
                
                @param plane the split plane
                @param rays contains the rays to be split. The rays are 
                           distributed into front and back rays.
                @param frontRays returns rays on the front side of the plane
                @param backRays returns rays on the back side of the plane
                
                @returns the number of splits
        */
        int SplitRays(const AxisAlignedPlane &plane,
                RayInfoContainer &rays, 
                RayInfoContainer &frontRays, 
                RayInfoContainer &backRays) const;

        int SplitViewCells(
                const AxisAlignedPlane &candidatePlane,
                const RayInfoContainer &rays,
                KdLeaf *leaf,
                ViewCellContainer &frontViewCells,
                ViewCellContainer &backViewCells,
                ViewCellContainer &frontAndBackViewCells) const;

        /** Adds the object to the pvs of the front and back leaf with a given classification.

                @param obj the object to be added
                @param cf the ray classification regarding the split plane
                @param frontPvs returns the PVS of the front partition
                @param backPvs returns the PVS of the back partition
        
        */
        void UpdateObjPvsContri(Intersectable *obj, 
                                         const int cf, 
                                         float &frontPvs, 
                                         float &backPvs, 
                                         float &totalPvs) const;
        
        /** Returns true if tree can be terminated.
        */
        inline bool LocalTerminationCriteriaMet(const OspTraversalData &data) const;

        /** Returns true if global tree can be terminated.
        */
        inline bool GlobalTerminationCriteriaMet(const OspTraversalData &data) const;

        float SelectSplitPlane(const OspTraversalData &tData,
                AxisAlignedPlane &plane,
                float &pFront,
                float &pBack);
        
        /** Propagates valid flag up the tree.
        */
        void PropagateUpValidity(KdNode *node);

        /** Writes the node to disk
                @note: should be implemented as visitor.
        */
#if ZIPPED_VIEWCELLS
        void ExportNode(KdNode *node, ogzstream &stream);
#else
        void ExportNode(KdNode *node, ofstream &stream);
#endif

        /** Returns estimated memory usage of tree.
        */
        float GetMemUsage() const;

        /** Evaluate the contributions of view cell volume of the left and the right view cell.
        */
        void EvalVolumeContribution(const VssRay &ray, 
                                                                        float &volLeft, 
                                                                        float &volRight);

        /** Evaluates the influence on the pvs of the event.
                @param ve the visibility event
                @param pvsLeft updates the left pvs
                @param rightPvs updates the right pvs
        */
        void EvalHeuristicsContribution(KdLeaf *leaf,
                const SortableEntry &ci,
                float &volLeft,
                float &volRight,
                int &pvsLeft,
                int &pvsRight);

        /** Prepares objects for the cost heuristics.
                @returns pvs size of the node
        */
        float PrepareHeuristics(const OspTraversalData &tData, int &numViewCells);

        /** Prepares heuristics for a particular ray.
        */
        float PrepareHeuristics(const VssRay &ray, int &numViewCells);

        /** Prepares construction for vsp and osp trees.
        */
        void ComputeBoundingBox(const ObjectContainer &objects,
                                                        AxisAlignedBox3 *forcedBoundingBox);

        void CollectDirtyCandidates(OspSplitCandidate *sc,
                vector<SplitCandidate *> &dirtyList);

        /** Collect view cells which see this kd leaf.
        */
        void CollectViewCells(KdLeaf *leaf, 
                ViewCellContainer &viewCells);

        /** Rays will be clipped to the bounding box.
        */
        void PreprocessRays(const VssRayContainer &sampleRays,
                RayInfoContainer &rays);

        /** Reads parameters from environment singleton.
        */
        void ReadEnvironment();

        /** Returns true if the specified ray end points is inside the kd leaf.
                @param isTermination if origin or termination point should be checked
        */
        bool EndPointInsideNode(KdLeaf *leaf, VssRay &ray, bool isTermination) const;

        void AddViewCellVolumeContri(
                ViewCell *vc, 
                float &frontVol, 
                float &backVol,
                float &frontAndBackVol) const;

        /** Classifies and mail view cell with respect to the heuristics contribution.
                Set view cell mail box according to it's influence on 
                front (0), back (1) and front / back node (2).
        */
        void  MailViewCell(ViewCell *vc, const int cf) const;

        int ClassifyRay(VssRay *ray, KdLeaf *leaf, const AxisAlignedPlane &plane) const;

        void EvalSubdivisionStats(const SplitCandidate &tData);

        void AddSubdivisionStats(const int viewCells,
                const float renderCostDecr,
                const float totalRenderCost);

        void EvalViewCellsForHeuristics(const VssRay &ray, 
                float &volLeft, 
                float &volRight);

        float EvalViewCellsVolume(KdLeaf *leaf, const RayInfoContainer &rays) const;
        
        int RemoveParentViewCellsPvs(KdLeaf *leaf, 
                                                                          const RayInfoContainer &rays
                                                                          ) const;

        int UpdateViewCellsPvs(KdLeaf *leaf, const RayInfoContainer &rays) const;
int OspTree::CheckViewCellsPvs(KdLeaf *leaf, 
                                                           const RayInfoContainer &rays) const;
        bool AddViewCellToObjectPvs(
                Intersectable *obj,
                ViewCell *vc, 
                float &contribution,
                bool onlyMailed) const;

protected:

        
        /// pointer to the hierarchy of view cells
        ViewCellsTree *mViewCellsTree;

        VspTree *mVspTree;

        /// The view cells manager
        ViewCellsManager *mViewCellsManager;

        /// candidates for placing split planes during cost heuristics
        vector<SortableEntry> *mSplitCandidates;

        /// Pointer to the root of the tree
        KdNode *mRoot;
                
        /// Statistics for the object space partition
        OspTreeStatistics mOspStats;
        
        /// box around the whole view domain
        AxisAlignedBox3 mBoundingBox;


        //-- local termination

        /// maximal possible depth
        int mTermMaxDepth;
        /// mininum probability
        float mTermMinProbability;
        /// minimal number of objects
        int mTermMinObjects;
        /// maximal contribution per ray
        float mTermMaxRayContribution;
        /// maximal acceptable cost ratio
        float mTermMaxCostRatio;
        /// tolerance value indicating how often the max cost ratio can be failed
        int mTermMissTolerance;


        //-- global criteria

        float mTermMinGlobalCostRatio;
        int mTermGlobalCostMissTolerance;
        int mGlobalCostMisses;

        /// maximal number of view cells
        int mTermMaxLeaves;
        /// maximal tree memory
        float mMaxMemory;
        /// the tree is out of memory
        bool mOutOfMemory;


        //-- split heuristics based parameters
        
        bool mUseCostHeuristics;
        /// balancing factor for PVS criterium
        float mCtDivCi; 
        /// if only driving axis should be used for split
        bool mOnlyDrivingAxis;
        
        /// current time stamp (used for keeping split history)
        int mTimeStamp;
        // if rays should be stored in leaves
        bool mStoreRays;

        /// epsilon for geometric comparisons
        float mEpsilon;

        /// subdivision stats output file
        ofstream  mSubdivisionStats;
        /// keeps track of cost during subdivision
        float mTotalCost;
        /// keeps track of overall pvs size during subdivision
        int mTotalPvsSize;
        /// number of currenly generated view cells
        int mCreatedLeaves;

        /// represents min and max band for sweep
        float mSplitBorder;

        /// weight between  render cost decrease and node render cost
        float mRenderCostDecreaseWeight;

        /// stores the kd node intersectables used for pvs
        KdIntersectableMap mKdIntersectables;


private:

        bool mCopyFromKdTree;
};


/** This class implements a structure holding two different hierarchies,
        one for object space partitioning and one for view space partitioning.

        The object space and the view space are subdivided using a cost heuristics.
        If an object space split or a view space split is chosen is also evaluated
        based on the heuristics. 
        
        The view space heuristics is evaluated by weighting and adding the pvss of the back and
        front node of each specific split. unlike for the standalone method vspbsp tree,
        the pvs of an object would not be the pvs of single object but that of all objects
        which are contained in the same leaf of the object subdivision. This could be done
        by storing the pointer to the object space partition parent, which would allow access to all children.
        Another possibility is to include traced kd-cells in the ray casing process.

        Accordingly, the object space heuristics is evaluated by storing a pvs of view cells with each object.
        the contribution to an object to the pvs is the number of view cells it can be seen from.

        @note
        There is a potential efficiency problem involved in a sense that once a certain type
        of split is chosen for view space / object space, the candidates for the next split of 
        object space / view space must be reevaluated.
        
*/
class HierarchyManager
{
public:
        /** Constructor taking an object space partition and a view space partition tree.
        */
        HierarchyManager(VspTree &vspTree, OspTree &ospTree);

        /** Constructs the view space and object space subdivision from a given set of rays
                and a set of objects.
                @param sampleRays the set of sample rays the construction is based on
                @param objects the set of objects
        */
        void Construct(const VssRayContainer &sampleRays,
                                   const ObjectContainer &objects,
                                   AxisAlignedBox3 *forcedViewSpace);

        /** Constructs first view cells, then object space partition.
        */
        void Construct2(const VssRayContainer &sampleRays,
                                        const ObjectContainer &objects,
                                        AxisAlignedBox3 *forcedViewSpace);

        /** Constructs only vsp tree.
        */
        void Construct3(const VssRayContainer &sampleRays,
                                        const ObjectContainer &objects,
                                        AxisAlignedBox3 *forcedViewSpace);

public:
        VspTree &mVspTree;
        OspTree &mOspTree;

protected:

        bool GlobalTerminationCriteriaMet(SplitCandidate *candidate) const;

        void PrepareConstruction(const VssRayContainer &sampleRays,
                const ObjectContainer &objects,
                AxisAlignedBox3 *forcedViewSpace,
                RayInfoContainer &viewSpaceRays,
                RayInfoContainer &objectSpaceRays);

        void RunConstruction(const bool repair);
        bool SubdivideSplitCandidate(SplitCandidate *sc);

        bool FinishedConstruction() const;

        SplitCandidate *NextSplitCandidate();

        void RepairQueue();

        void CollectDirtyCandidates(vector<SplitCandidate *> &dirtyList);

        VspTree::VspSplitCandidate *PrepareVsp(const VssRayContainer &sampleRays,
                                                           AxisAlignedBox3 *forcedViewSpace,
                                                           RayInfoContainer &rays);

        OspTree::OspSplitCandidate *PrepareOsp(const VssRayContainer &sampleRays,
                const ObjectContainer &objects,
                AxisAlignedBox3 *forcedObjectSpace,
                RayInfoContainer &rays);

        void EvalSubdivisionStats(const SplitCandidate &tData);

        void AddSubdivisionStats(const int splits,
                const float renderCostDecr,
                const float totalRenderCost);


protected:

        AxisAlignedBox3 mBoundingBox;

        SplitQueue mTQueue;

        SplitCandidate *mCurrentCandidate;

        //-- global criteria
        float mTermMinGlobalCostRatio;
        int mTermGlobalCostMissTolerance;
        int mGlobalCostMisses;

        /// keeps track of cost during subdivision
        float mTotalCost;

        ofstream mSubdivisionStats;
};

}

#endif