source: GTP/trunk/Lib/Vis/Preprocessing/src/BvHierarchy.h @ 2199

#ifndef _BvHierarchy_H__
#define _BvHierarchy_H__

#include <stack>

#include "Mesh.h"
#include "Containers.h"
#include "Statistics.h"
#include "VssRay.h"
#include "RayInfo.h"
#include "gzstream.h"
#include "SubdivisionCandidate.h"
#include "AxisAlignedBox3.h"
#include "IntersectableWrapper.h"
#include "HierarchyManager.h"
#include "PerfTimer.h"


namespace GtpVisibilityPreprocessor {


class ViewCellLeaf;
class Plane3;
class AxisAlignedBox3;
class Ray;
class ViewCellsStatistics;
class ViewCellsManager;
class MergeCandidate;
class Beam;
class ViewCellsTree;
class Environment;
class BvhInterior;
class BvhLeaf;
class BvhNode;
class BvhTree;
class VspTree;
class HierarchyManager;


/** View space partition statistics.
*/
class BvhStatistics: public StatisticsBase
{
public:
        
        /// Constructor
        BvhStatistics() 
        {
                Reset();
        }

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

        double AvgObjectRefs() const 
        { return objectRefs / (double)Leaves(); } 

        double AvgRayRefs() const 
        { return rayRefs / (double)Leaves(); } 

        
        void Reset() 
        {
                nodes = 0;
                splits = 0;
                maxDepth = 0;

                minDepth = 99999;
                accumDepth = 0;
        maxDepthNodes = 0;
                minProbabilityNodes = 0;
                maxCostNodes = 0;
                ///////////////////
                minObjectsNodes = 0;
                maxObjectRefs = 0;
                minObjectRefs = 999999999;
                objectRefs = 0;
                emptyNodes = 0;

                ///////////////////
                minRaysNodes = 0;
                maxRayRefs = 0;
                minRayRefs = 999999999;
                rayRefs = 0;
                maxRayContriNodes = 0;
                mGlobalCostMisses = 0;
        }


public:

        // total number of nodes
        int nodes;
        // number of splits
        int splits;
        // maximal reached depth
        int maxDepth;
        // minimal depth
        int minDepth;
        // max depth nodes
        int maxDepthNodes;
        // accumulated depth (used to compute average)
        int accumDepth;
        // minimum area nodes
        int minProbabilityNodes;
        /// nodes termination because of max cost ratio;
        int maxCostNodes;
        // global cost ratio violations
        int mGlobalCostMisses;

        //////////////////
        // nodes with minimum objects
        int minObjectsNodes;
        // max number of rays per node
        int maxObjectRefs;
        // min number of rays per node
        int minObjectRefs;
        /// object references
        int objectRefs;
        // leaves with no objects
        int emptyNodes;

        //////////////////////////
        // nodes with minimum rays
        int minRaysNodes;
        // max number of rays per node
        int maxRayRefs;
        // min number of rays per node
        int minRayRefs;
        /// object references
        int rayRefs;
        /// nodes with max ray contribution
        int maxRayContriNodes;

        void Print(std::ostream &app) const;

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


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

        BvhNode();
        BvhNode(const AxisAlignedBox3 &bbox);
        BvhNode(const AxisAlignedBox3 &bbox, BvhInterior *parent);

        virtual ~BvhNode(){};

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

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

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

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

        /** collects all objects under this node.
        */
        virtual void CollectObjects(ObjectContainer &objects) = 0;

        /** The bounding box specifies the node extent.
        */
        inline 
        AxisAlignedBox3 GetBoundingBox() const
        { return mBoundingBox; }

        /** Sets bouding box of this node.
        */
        inline 
        void SetBoundingBox(const AxisAlignedBox3 &boundingBox) 
        { mBoundingBox = boundingBox; }

        /** Cost of mergin this node.
        */
        float GetMergeCost() {return (float)-mTimeStamp; }

        virtual int GetRandomEdgePoint(Vector3 &point, Vector3 &normal);

        inline int GetTimeStamp() const { return mTimeStamp; }
        inline void SetTimeStamp(const int timeStamp) { mTimeStamp = timeStamp; };


        ////////////////////////
        //-- inherited functions from Intersectable

        AxisAlignedBox3 GetBox() const { return mBoundingBox; }
        
        int CastRay(Ray &ray) { return 0; }
        
        bool IsConvex() const { return true; }
        bool IsWatertight() const { return true; }
        float IntersectionComplexity() { return 1; }
  
        int NumberOfFaces() const { return 6; };
        
        int GetRandomSurfacePoint(GtpVisibilityPreprocessor::Vector3 &point, 
                                                          GtpVisibilityPreprocessor::Vector3 &normal)
        {
                // TODO
                return 0;
        }

        int GetRandomVisibleSurfacePoint(GtpVisibilityPreprocessor::Vector3 &point,
                                                                         GtpVisibilityPreprocessor::Vector3 &normal,
                                                                         const GtpVisibilityPreprocessor::Vector3 &viewpoint,
                                                                         const int maxTries)
        {
                // TODO
                return 0;
        }
  
        int Type() const
        {
                return Intersectable::BVH_INTERSECTABLE;
        }

        std::ostream &Describe(std::ostream &s) { return s; }

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

        float mRenderCost;

protected:
        
        /// the bounding box of the node
        AxisAlignedBox3 mBoundingBox;
        /// parent of this node
        BvhInterior *mParent;
        int mTimeStamp;
};


/** BSP interior node implementation 
*/
class BvhInterior: public BvhNode 
{
public:
        /** Standard contructor taking a bounding box as argument.
        */
        BvhInterior(const AxisAlignedBox3 &bbox);
        BvhInterior(const AxisAlignedBox3 &bbox, BvhInterior *parent);

        ~BvhInterior();
        /** @return false since it is an interior node 
        */
        bool IsLeaf() const;
        
        BvhNode *GetBack() { return mBack; }
        BvhNode *GetFront() { return mFront; }

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

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

        friend std::ostream &operator<<(std::ostream &s, const BvhInterior &A)
        {
                return s << A.mBoundingBox;
        }

        virtual void CollectObjects(ObjectContainer &objects);

protected:

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


/** BSP leaf node implementation.
*/
class BvhLeaf: public BvhNode 
{
public:
        /** Standard contructor taking a bounding box as argument.
        */
        BvhLeaf(const AxisAlignedBox3 &bbox);
        BvhLeaf(const AxisAlignedBox3 &bbox, BvhInterior *parent);
        BvhLeaf(const AxisAlignedBox3 &bbox, BvhInterior *parent, const int numObjects);

        ~BvhLeaf();

        /** @return true since it is an interior node 
        */
        bool IsLeaf() const;
        
        SubdivisionCandidate *GetSubdivisionCandidate()// const
        { 
                return mSubdivisionCandidate; 
        }

        void SetSubdivisionCandidate(SubdivisionCandidate *candidate)
        { 
                mSubdivisionCandidate = candidate; 
        }
        
        virtual void CollectObjects(ObjectContainer &objects);

        /** Returns level of the hierarchy that is "active" right now.
        */
        BvhNode *GetActiveNode()
        {
                return mActiveNode;
        }

        /** Returns level of the hierarchy that is "active" right now.
        */
        void SetActiveNode(BvhNode *node)
        {
                mActiveNode = node;
        }

public:
  // gl list use to store the geometry on the gl server
  int mGlList;
  
  /// objects
  ObjectContainer mObjects;
  
  
protected:
  
  /// pointer to a split plane candidate splitting this leaf
  SubdivisionCandidate *mSubdivisionCandidate;
  
  /// the active node which will be accounted for in the pvs
  BvhNode *mActiveNode;
};


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

protected:
        struct SortableEntry;
        typedef vector<SortableEntry> SortableEntryContainer;

public:
        
        /** Additional data which is passed down the BSP tree during traversal.
        */
        class BvhTraversalData
        {  
        public:
                
                BvhTraversalData():
                mNode(NULL),
                mDepth(0),
                mMaxCostMisses(0), 
                mAxis(0),
                mNumRays(0),
                mCorrectedPvs(0),
                mPvs(0),
                mCorrectedVolume(0),
                mVolume(0)
                {
                        for (int i = 0; i < 4; ++ i)
                                mSortedObjects[i] = NULL;
                }
                
                BvhTraversalData(BvhLeaf *node, 
                                                 const int depth,
                                                 const float v,
                                                 const int numRays):
                mNode(node), 
                mDepth(depth),
                mMaxCostMisses(0),
                mAxis(0),
                mNumRays(numRays),
                mCorrectedPvs(0),
                mPvs(0),
                mCorrectedVolume(0),
                mVolume(v)
                {
                        for (int i = 0; i < 4; ++ i)
                                mSortedObjects[i] = NULL;
                }

                /** Deletes contents and sets them to NULL.
                */
                void Clear()
                {
                        DEL_PTR(mNode);
                        for (int i = 0; i < 4; ++ i)
                                DEL_PTR(mSortedObjects[i]);
                }

                /// the current node
                BvhLeaf *mNode;
                /// current depth
                int mDepth;
                /// the volume of the node
                float mVolume;
                /// the corrected volume
                float mCorrectedVolume;
                /// how often this branch has missed the max-cost ratio
                int mMaxCostMisses;
                /// current axis
                int mAxis;
                /// number of rays
                int mNumRays;
                /// parent Pvs;
                float mPvs;
                /// parent pvs correction factor
                float mCorrectedPvs;

                /// the sorted objects for the three dimensions
                ObjectContainer *mSortedObjects[4];             
    };


        /** Candidate for a object space split.
        */
        class BvhSubdivisionCandidate: public SubdivisionCandidate
        {  
        public:

        BvhSubdivisionCandidate(const BvhTraversalData &tData): mParentData(tData)
                {};

                ~BvhSubdivisionCandidate() 
                { 
                        mParentData.Clear(); 
                }

                int Type() const { return OBJECT_SPACE; }
        
                void EvalCandidate(bool computeSplitplane = true)
                {
            mDirty = false;
                        sBvHierarchy->EvalSubdivisionCandidate(*this, computeSplitplane);
                }

                bool Apply(SplitQueue &splitQueue, bool terminationCriteriaMet)
                {
                        BvhNode *n = sBvHierarchy->Subdivide(splitQueue, this, terminationCriteriaMet);

                        // local or global termination criteria failed
                        return !n->IsLeaf();            
                }

                void CollectDirtyCandidates(SubdivisionCandidateContainer &dirtyList,
                                                                        const bool onlyUnmailed)
                {
                        sBvHierarchy->CollectDirtyCandidates(this, dirtyList, onlyUnmailed);
                }

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

                BvhSubdivisionCandidate(const ObjectContainer &frontObjects, 
                                                                const ObjectContainer &backObjects, 
                                                                const BvhTraversalData &tData): 
                mFrontObjects(frontObjects), mBackObjects(backObjects), mParentData(tData)
                {}

                float GetPriority() const
                {
                        //return (float)-mParentData.mDepth;
                        return mPriority;
                }

                /////////////////////////////7

                /// pointer to parent tree.
                static BvHierarchy *sBvHierarchy;

                /// parent data
                BvhTraversalData mParentData;
                /// the objects on the front of the potential split
                ObjectContainer mFrontObjects;
                /// the objects on the back of the potential split
                ObjectContainer mBackObjects;
                        
                float mCorrectedFrontPvs;
                float mCorrectedBackPvs;

                float mCorrectedFrontVolume;
                float mCorrectedBackVolume;
        };

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


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

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

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

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

        /** Evaluates candidate for splitting.
        */
        void EvalSubdivisionCandidate(BvhSubdivisionCandidate &splitData, 
                                                                  bool computeSplitPlane = true);

        /** Returns vector of leaves.
        */
        void CollectLeaves(BvhNode *root, vector<BvhLeaf *> &leaves) const;

        /** Returns vector of leaves.
        */
        void CollectNodes(BvhNode *root, vector<BvhNode *> &nodes) const;

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

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

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

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

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

        /** 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);

        float GetViewSpaceVolume() const;
        /** Writes tree to output stream
        */
        bool Export(OUT_STREAM &stream);

        /** Collects rays associated with the objects.
        */
        void CollectRays(const ObjectContainer &objects, VssRayContainer &rays) const;

        /** 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 leaf the point pt lies in, starting from root.
        */
        BvhLeaf *GetLeaf(Intersectable *obj, BvhNode *root = NULL) const;

        /** Sets a pointer to the view cells tree.
        */
        ViewCellsTree *GetViewCellsTree() const { return mViewCellsTree; }
        
        /** See Get
        */
        void SetViewCellsTree(ViewCellsTree *vt) { mViewCellsTree = vt; }

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

        /** Sets this node to be an active node.
        */
        void SetActive(BvhNode *node) const;


        ///////////////////////////
        // hacks in order to provide interleaved heurisitcs

        BvhNode *SubdivideAndCopy(SplitQueue &tQueue, SubdivisionCandidate *splitCandidate);

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

        static float EvalAbsCost(const ObjectContainer &objects);

        void CollectObjects(const AxisAlignedBox3 &box, ObjectContainer &objects);

        float GetRenderCostIncrementially(BvhNode *node) const;

        void Compress();
        void CreateUniqueObjectIds();

        PerfTimer mNodeTimer;
        PerfTimer mSubdivTimer;
        PerfTimer mEvalTimer;
        PerfTimer mSplitTimer;
        PerfTimer mPlaneTimer;
        PerfTimer mSortTimer;
        PerfTimer mCollectTimer;

protected:

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

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

        /** For sorting the objects during the heuristics
        */
        struct SortableEntry
        {
                Intersectable *mObject;
                float mPos;

                SortableEntry() {}

                SortableEntry(Intersectable *obj, const float pos): 
                mObject(obj), mPos(pos)
                {}

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

        /** Evaluate balanced object partition.
        */
        float EvalLocalObjectPartition(const BvhTraversalData &tData,
                                                                   const int axis,
                                                                   ObjectContainer &objectsFront,
                                                                   ObjectContainer &objectsBack);

        /** Evaluate surface area heuristic for the node.
        */
        float EvalSah(const BvhTraversalData &tData,
                                  const int axis,
                                  ObjectContainer &objectsFront,
                                  ObjectContainer &objectsBack);


        /** Evaluates render cost of the bv induced by these objects
        */
        float EvalRenderCost(const ObjectContainer &objects);// const;

        /** Evaluates tree stats in the BSP tree leafs.
        */
        void EvaluateLeafStats(const BvhTraversalData &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
        */
        BvhNode *Subdivide(SplitQueue &tQueue, 
                                           SubdivisionCandidate *splitCandidate,
                                           const bool globalCriteriaMet);
        
        /** Subdivides leaf.
                @param sc the subdivisionCandidate holding all necessary data for subdivision           
                
                @param frontData returns the traversal data for the front node
                @param backData returns the traversal data for the back node

                @returns the new interior node = the of the subdivision
        */
        BvhInterior *SubdivideNode(const BvhSubdivisionCandidate &sc,
                                                           BvhTraversalData &frontData,
                                                           BvhTraversalData &backData);

        /** Splits the objects for the next subdivision.
                @returns cost for this split
        */
        float SelectObjectPartition(const BvhTraversalData &tData,
                                                                ObjectContainer &frontObjects,
                                                                ObjectContainer &backObjects,
                                                                bool useVisibilityBasedHeuristics);
        
        /** Writes the node to disk
                @note: should be implemented as visitor.
        */
        void ExportNode(BvhNode *node, OUT_STREAM &stream);

        /** Exports objects associated with this leaf.
        */
        void ExportObjects(BvhLeaf *leaf, OUT_STREAM &stream);

        /** Associates the objects with their bvh leaves.
        */
        static void AssociateObjectsWithLeaf(BvhLeaf *leaf);

        
        /////////////////////////////
        // Helper functions for local cost heuristics
        
        /** Prepare split candidates for cost heuristics using axis aligned splits.
                @param node the current node
                @param axis the current split axis
        */
        void PrepareLocalSubdivisionCandidates(const BvhTraversalData &tData,
                                                                                   const int axis);

        static void CreateLocalSubdivisionCandidates(const ObjectContainer &objects, 
                                                                                                 SortableEntryContainer **subdivisionCandidates,
                                                                                                 const bool sort,
                                                                                                 const int axis);

        float EvalPriority(const BvhSubdivisionCandidate &splitCandidate,
                                           const float renderCostDecr,
                                           const float oldRenderCost) const;

        /** Computes object partition with the best cost according to the heurisics.
                @param tData the traversal data
                @param axis the split axis
                @param objectsFront the objects in the front child bv
                @param objectsBack the objects in the back child bv
                @param backObjectsStart the iterator marking the position where the back objects begin

                @returns relative cost (relative to parent cost)
        */
        float EvalLocalCostHeuristics(const BvhTraversalData &tData,
                                                                  const int axis,
                                                                  ObjectContainer &objectsFront,
                                                                  ObjectContainer &objectsBack);

        /** Evaluates the contribution to the front and back volume
                when this object is changing sides in the bvs.

                @param object the object
                @param volLeft updates the left pvs
                @param volPvs updates the right pvs
        */
        void EvalHeuristicsContribution(Intersectable *obj,
                                                                        float &volLeft, 
                                                                        float &volRight);

        /** Prepares objects for the cost heuristics.
                @returns sum of volume of associated view cells
        */
        float PrepareHeuristics(const BvhTraversalData &tData, const int axis);
        
        /** Evaluates cost for a leaf given the surface area heuristics.
        */
        float EvalSahCost(BvhLeaf *leaf) const;

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


        /** Prepares construction for vsp and osp trees.
        */
        AxisAlignedBox3 EvalBoundingBox(const ObjectContainer &objects, 
                                                                        const AxisAlignedBox3 *parentBox = NULL) const;

        /** Collects list of invalid candidates. Candidates
                are invalidated by a view space subdivision step
                that affects this candidate.
        */
        void CollectDirtyCandidates(BvhSubdivisionCandidate *sc,
                                                                vector<SubdivisionCandidate *> &dirtyList,
                                                                const bool onlyUnmailed);

        /** Collect view cells which see this bvh leaf.
        */
        int CollectViewCells(const ObjectContainer &objects, 
                                                 ViewCellContainer &viewCells,
                                                 const bool setCounter,
                                                 const bool onlyUnmailedRays);// const;

        /** Collects view cells which see an object.
                @param useMailBoxing if mailing should be used and
                only unmailed object should pass
                @param setCounter counter for the sweep algorithm
                @param onlyUnmailedRays if only unmailed rays should be considered
        */
        int CollectViewCells(Intersectable *object, 
                                                 ViewCellContainer &viewCells, 
                                                 const bool useMailBoxing,
                                                 const bool setCounter,
                                                 const bool onlyUnmailedRays);// const;

        /** Counts the view cells of this object. note: only
                counts unmailed objects.
        */
        int CountViewCells(Intersectable *obj);// const;

        /** Counts the view cells seen by this bvh leaf
        */
        int CountViewCells(const ObjectContainer &objects);// const;

#if STORE_VIEWCELLS_WITH_BVH

        int AssociateViewCellsWithObject(Intersectable *obj, const bool useMailBoxing) const;

        void AssociateViewCellsWithObjects(const ObjectContainer &objects) const;

        void ReleaseViewCells(const ObjectContainer &objects);

        int CollectViewCellsFromRays(Intersectable *obj, 
                                                                 ViewCellContainer &viewCells,
                                                                 const bool useMailBoxing,
                                                                 const bool setCounter,
                                                                 const bool onlyUnmailedRays);

        int CountViewCellsFromRays(Intersectable *obj);
#endif

        /** Evaluates increase in pvs size.
        */
        int EvalPvsEntriesIncr(BvhSubdivisionCandidate &splitCandidate, 
                                                   const float avgRayContri);// const;

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

        /** Print the subdivision stats in the subdivison log.
        */
        void PrintSubdivisionStats(const SubdivisionCandidate &tData);

        /** Prints out the stats for this subdivision.
        */
        void AddSubdivisionStats(const int viewCells,
                                                         const float renderCostDecr,
                                                         const float totalRenderCost);

        /** Stores rays with objects that see the rays.
        */
        int AssociateObjectsWithRays(const VssRayContainer &rays) const;

        /** Tests if object is in this leaf.
                @note: assumes that objects are sorted by their id.
        */
        bool IsObjectInLeaf(BvhLeaf *, Intersectable *object) const;

        /** Prepares the construction of the bv hierarchy and returns
                the first subdivision candidate.
        */
        void PrepareConstruction(SplitQueue &tQueue,
                                                         const VssRayContainer &sampleRays,
                                                         const ObjectContainer &objects);

        /** Resets bv hierarchy. E.g. deletes root and resets stats.
        */
        void Reset(SplitQueue &tQueue,
                           const VssRayContainer &rays, 
                           const ObjectContainer &objects);

        /** Evaluates volume of view cells that see the objects.
        */
        float EvalViewCellsVolume(const ObjectContainer &objects);// const;

        /** Assigns or newly creates initial list of sorted objects.
        */
        void AssignInitialSortedObjectList(BvhTraversalData &tData,
                                                                           const ObjectContainer &objects);

        /** Assigns sorted objects to front and back data.
        */
        void AssignSortedObjects(const BvhSubdivisionCandidate &sc,
                                                         BvhTraversalData &frontData,
                                                         BvhTraversalData &backData);
        
        /** Creates new root of hierarchy and computes bounding box.
                Has to be called before the preparation of the subdivision.
        */
        void Initialise(const ObjectContainer &objects);


        ////////////////////
        // initial subdivision

        /** Makes an initial parititon of the object space based on
                some criteria (size, shader)
        */
        void ApplyInitialSubdivision(SubdivisionCandidate *firstCandidate,
                                                                 vector<SubdivisionCandidate *> &candidateContainer);

        void ApplyInitialSplit(const BvhTraversalData &tData,
                                                   ObjectContainer &frontObjects,
                                                   ObjectContainer &backObjects);

        bool InitialTerminationCriteriaMet(const BvhTraversalData &tData) const;

        /** Sets the bvh node ids.
        */
        void SetUniqueNodeIds();

protected:
        
        /// pre-sorted subdivision candidtes for all three directions.
        vector<SortableEntry> *mGlobalSubdivisionCandidates[3];
        /// pointer to the hierarchy of view cells
        ViewCellsTree *mViewCellsTree;
        /// The view cells manager
        ViewCellsManager *mViewCellsManager;
        /// candidates for placing split planes during cost heuristics
        vector<SortableEntry> *mSubdivisionCandidates;
        /// Pointer to the root of the tree
        BvhNode *mRoot;
        /// Statistics for the object space partition
        BvhStatistics mBvhStats;        
        /// box around the whole view domain
        AxisAlignedBox3 mBoundingBox;
        /// the hierarchy manager
        HierarchyManager *mHierarchyManager;


        ////////////////////
        //-- local termination criteria

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


        ////////////////////
        //-- global termination criteria

        /// the minimal accepted global cost ratio
        float mTermMinGlobalCostRatio;
        //// number of accepted misses of the global cost ratio
        int mTermGlobalCostMissTolerance;
        /// maximal number of view cells
        int mTermMaxLeaves;
        /// maximal tree memory
        float mMaxMemory;
        /// the tree is out of memory
        bool mOutOfMemory;


        ////////////////////////////////////////
        //-- split heuristics based parameters
        
        /// if a heuristics should be used for finding a split plane
    bool mUseCostHeuristics;
        /// if sah heuristcs should be used for finding a split plane
        bool mUseSah;
    /// 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;
        // subdivision stats output file
        std::ofstream  mSubdivisionStats;
        /// keeps track of cost during subdivision
        float mTotalCost;
        int mPvsEntries;
        /// 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;

        /// if the objects should be sorted in one global step
        bool mUseGlobalSorting;

        bool mUseBboxAreaForSah;

        //SortableEntryContainer *mSortedObjects[4];

        int mMinRaysForVisibility;

        /// constant value for driving the heuristics
        float mMemoryConst;

        int mMaxTests;

        bool mIsInitialSubdivision;

        bool mApplyInitialPartition;
        
        int mInitialMinObjects;
        float mInitialMaxAreaRatio;
        float mInitialMinArea;
};

}

#endif