source: GTP/trunk/Lib/Vis/Preprocessing/src/Pvs.h @ 2019

#ifndef __PVS_H
#define __PVS_H

#include <map>
#include <vector>
#include "common.h"
#include <math.h>
using namespace std;

namespace GtpVisibilityPreprocessor {

class KdNode;
class BspNode;
class Ray;
class Intersectable;
class ViewCell;


/** Information stored with a PVS entry. Consists of the number
        the object was seen from the view cell.
*/
template<typename T, typename S>
struct PvsEntry 
{
public:

        PvsEntry() {}

        PvsEntry(T sample, const S &data): mObject(sample), mData(data) {}

        T mObject;
        S mData;

        template<typename T, typename S>
        friend int operator< (const PvsEntry<T, S> &a, const PvsEntry<T, S> &b);
        template<typename T, typename S>
        friend int operator== (const PvsEntry<T, S> &a, const PvsEntry<T, S> &b);
};


template<typename T, typename S>
int operator< (const PvsEntry<T, S> &a, const PvsEntry<T, S> &b)
{
        return a.mObject < b.mObject;
} 

template<typename T, typename S>
int operator== (const PvsEntry<T, S> &a, const PvsEntry<T, S> &b)
{
        return a.mObject == b.mObject;
} 


template<typename T, typename S>
struct LtSample
{
    bool operator()(const PvsEntry<T, S> &a, const PvsEntry<T, S> &b) const
    {
                return a.mObject < b.mObject;
        } 
};

template<typename T, typename S>
int equalSample (const PvsEntry<T, S> &a, const PvsEntry<T, S> &b)
{
        return a.mObject == b.mObject;
} 

/** Information stored with a PVS entry. Consists of the number
        the object was seen from the view cell.
*/
struct PvsData {
public:
        PvsData() {}
        PvsData(const float sumPdf):
        mSumPdf(sumPdf) {}
        
        // $$JB in order to return meaningfull values
        // it assumes that the sum pdf has been normalized somehow!!!
        inline float GetVisibility() 
        { 
                return mSumPdf; 
        }

        /// sum of probability density of visible sample rays
        float mSumPdf;
};


class MailablePvsData 
{
public:
        // sum of probability density of visible sample rays
        float mSumPdf;
        int mCounter;

        MailablePvsData() {}
        MailablePvsData(const float sumPdf):
        mSumPdf(sumPdf) {}

        // $$JB in order to return meaningfull values
        // it assumes that the sum pdf has been normalized somehow!!!
        float GetVisibility() 
        { 
                return mSumPdf; 
        }

        ////////////////////////////
        //  Mailing stuff

        // last mail id -> warning not thread safe!
        // both mailId and mailbox should be unique for each thread!!!
        static int sMailId;
        static int sReservedMailboxes;

        static void NewMail(const int reserve = 1) {
                sMailId += sReservedMailboxes;
                sReservedMailboxes = reserve;
        }

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

        void Mail(const int mailbox) { mMailbox = sMailId + mailbox; }
        bool Mailed(const int mailbox) const { return mMailbox == sMailId + mailbox; }

        int IncMail() { return ++ mMailbox - sMailId; }
        
        //////////////////////////////////////////

protected:

        int mMailbox;

};


template<typename T, typename S>
class PvsIterator
{
public:
PvsIterator<T, S>(){}
        PvsIterator<T, S>(const typename vector<PvsEntry<T, S> >::const_iterator &itCurrent,
                                          const typename vector<PvsEntry<T, S> >::const_iterator &itEnd):
        mItCurrent(itCurrent), mItEnd(itEnd)
        {
        }

        bool HasMoreEntries() const 
        {
                return (mItCurrent != mItEnd);
        }

        const PvsEntry<T, S> &Next()
        {
                return *(mItCurrent ++);
        }
        
private:
        typename vector<PvsEntry<T, S> >::const_iterator mItCurrent;
        typename vector<PvsEntry<T, S> >::const_iterator mItEnd;
};


/** Template class representing the Potentially Visible Set (PVS) 
        mainly from a view cell, but also e.g., from objects.
*/
template<typename T, typename S>
class Pvs
{
        template<typename T, typename S>
        friend class PvsIterator;

public:
  
        Pvs(): mSamples(0), mEntries(), mLastSorted(0), mQueriesSinceSort(0) {}

        /** creates pvs and initializes it with the given entries. 
                Assumes that entries are sorted-
        */
        Pvs(const vector<PvsEntry<T, S> > &samples);
        virtual ~Pvs() {};

        /** Compresses PVS lossless or lossy.
        */
        int Compress() {return 0;}
        int GetSize() const {return (int)mEntries.size();}
        bool Empty() const {return mEntries.empty();}

        void Reserve(const int n) { mEntries.reserve(n); }

        /** Normalize the visibility of entries in order to get 
                comparable results.
        */
        void NormalizeMaximum();

        /** Merges pvs of a into this pvs.
                Warning: very slow!
        */
        void MergeInPlace(const Pvs<T, S> &a);

        /** Difference of pvs to pvs b.
                @returns number of different entries.
        */
        int Diff(const Pvs<T, S> &b);

        /** Finds sample in PVS.
                @param checkDirty if dirty part of the pvs should be checked for entry 
                        (warning: linear runtime in dirty part)
                @returns iterator on the sample.
        */
        bool Find(T sample,
                          typename vector<PvsEntry<T, S> >::iterator &it,
                          const bool checkDirty = true);

        bool GetSampleContribution(T sample, const float pdf, float &contribution);

        /** Adds sample to PVS.
                @returns contribution of sample (0 or 1)
        */
        float AddSample(T sample, const float pdf);

        /** Adds sample to PVS without checking for presence of the sample
                pvs remains unsorted!
        */
        void AddSampleDirty(T sample, const float pdf);

        /** Adds sample dirty (on the end of the vector) but
                first checks if sample is already in clean part of the pvs.
        */
        bool AddSampleDirtyCheck(T sample, const float pdf);//, float &contribution);

        /** Sort pvs entries - this should always be called after a
                sequence of AddSampleDirty calls 
        */
        void Sort();

  /** Sort pvs entries assume that the pvs contains unique entries
   */
  void SimpleSort();

        /** Adds sample to PVS. Assumes that the pvs is sorted
                @returns contribution of sample (0 or 1)
        */
        //float AddSamples(const vector<PvsEntry<T, S> > &samples);

        /** Adds sample to PVS.
                @returns PvsData
        */
        typename std::vector<PvsEntry<T, S> >::iterator AddSample2(T sample, const float pdf);

        /** Subtracts one pvs from another one.
                WARNING: could contains bugs
                @returns new pvs size
        */
        int SubtractPvs(const Pvs<T, S> &pvs);

        /** Returns PVS data, i.e., how often it was seen from the view cell, 
                and the object itsef.
        */
        void GetData(const int index, T &entry, S &data);

        /** Collects the PVS entries and returns them in the vector.
        */
        void CollectEntries(std::vector<T> &entries);

        /** Removes sample from PVS if reference count is zero.
                @param visibleSamples number of references to be removed
        */
        bool RemoveSample(T sample, const float pdf);

        /** Compute continuous PVS difference 
        */
        void ComputeContinuousPvsDifference(Pvs<T, S> &pvs, 
                                                                                float &pvsReduction,
                                                                                float &pvsEnlargement);

        /** Clears the pvs.
        */
        void Clear(const bool trim = true);

        void Trim();

        static int GetEntrySizeByte(); 
        static float GetEntrySize();

        /** Compute continuous PVS difference 
        */
        float GetPvsHomogenity(Pvs<T, S> &pvs);

        static void Merge(Pvs<T, S> &mergedPvs, const Pvs<T, S> &a, const Pvs<T, S> &b);

        static void Merge(Pvs<T, S> &mergedPvs, 
                                          const typename std::vector<PvsEntry<T, S> >::const_iterator &aBegin,
                                          const typename std::vector<PvsEntry<T, S> >::const_iterator &aEnd,
                                          const typename std::vector<PvsEntry<T, S> >::const_iterator &bBegin,
                                          const typename std::vector<PvsEntry<T, S> >::const_iterator &bEnd,
                                          const int aSamples, 
                                          const int bSamples);

        int GetSamples() const
        {
                return mSamples;
        }


        bool IsDirty() const
        {
                return mLastSorted < mEntries.size();
        }

        bool RequiresResort() const
        {
          // the last part should not be more than log of the sorted part. this
          // way we can achieve logarithmic behaviour for insertion and find
          const int n = mEntries.size();
          const int dirtySize = n - mLastSorted;

#define LOG2E 1.442695040f
          
          const float logN = log((float)max(1, n))/LOG2E;
          const float logS = log((float)max(1, mLastSorted))/LOG2E;
          const float logD = log((float)max(1, dirtySize))/LOG2E;
          
          if (8*(n + 2*dirtySize*logD) <
                  mQueriesSinceSort*((mLastSorted*logS + dirtySize*dirtySize/2)/n - logN)) {
                //              cout<<"Q="<<mQueriesSinceSort<<" N="<<n<<" D="<<dirtySize<<endl;
                return true;
          }
          return false;
        }

  bool RequiresResortLog() const
  {
        // the last part should not be more than log of the sorted part. this
        // way we can achieve logarithmic behaviour for insertion and find
        const int dirtySize = (int)mEntries.size() - mLastSorted;
        return dirtySize > 4*(int)(log((double)mEntries.size()) / log(2.0));
  }
  
  
        int GetLastSorted() const
        {
                return mLastSorted;
        }

        typename PvsIterator<T, S> GetIterator() const;

protected:

        /// vector of PVS entries
        vector<PvsEntry<T, S> > mEntries; 
        
        /// Number of samples used to create the PVS
        int mSamples;
  
        /// Last sorted entry in the pvs (important for find and merge)
        int mLastSorted;

  int mQueriesSinceSort;
};


template <typename T, typename S>
Pvs<T, S>::Pvs(const vector<PvsEntry<T, S> > &samples)
{
        mEntries.reserve(samples.size());
        mEntries = samples;
        mLastSorted = 0;
        mSamples = samples.size();
}


template <typename T, typename S>
void Pvs<T, S>::Sort()
{
        std::vector<PvsEntry<T, S> >::iterator it = mEntries.begin() + mLastSorted;
        //std::vector<PvsEntry<T, S> >::const_iterator it = mEntries.begin() + mLastSorted;
        std::vector<PvsEntry<T, S> >::iterator it_end = mEntries.end();

        // throw out double entries
        std::vector<PvsEntry<T, S> >::iterator newEnd = unique(it, it_end);
        sort(it, newEnd);
        //sort(mEntries.begin(), mEntries.end());
        
        // now merge sorted ranges
        ObjectPvs newPvs;
        Merge(newPvs, 
                  mEntries.begin(),
                  it, 
                  it,
                  newEnd, 
                  mSamples,
                  0);
        
        mEntries = newPvs.mEntries;
        mLastSorted = (int)mEntries.size();
        mQueriesSinceSort = 0;
}

template <typename T, typename S>
void Pvs<T, S>::SimpleSort()
{
  //  sort(mEntries.begin(), mEntries.end());
  std::vector<PvsEntry<T, S> >::iterator it = mEntries.begin() + mLastSorted;
  
  sort(it, mEntries.end());
  inplace_merge(mEntries.begin(), it, mEntries.end());
  
  mLastSorted = (int)mEntries.size();
  mQueriesSinceSort = 0;
}


/**
   Compute continuous PVS difference of 'b' with respect to the base PVS (*this).
   Provides separatelly PVS reduction from PVS enlargement.

*/
template <typename T, typename S>
void
Pvs<T, S>::ComputeContinuousPvsDifference(Pvs<T, S> &b,
                                                                                  float &pvsReduction,
                                                                                  float &pvsEnlargement)
{
        pvsReduction = 0.0f;
        pvsEnlargement = 0.0f;

        // Uses sum of log differences, which corresponds to entropy
        std::vector<PvsEntry<T, S> >::iterator it;

        for (it = b.mEntries.begin(); it != b.mEntries.end(); ++ it) 
        {
                float bSumPdf = (*it).mData.mSumPdf;
                float aSumPdf = 0.0f;

                vector<PvsEntry<T, S> >::iterator oit;
                const bool entryFound = Find((*it).mObject, oit);               

                if (entryFound)
                {
                        aSumPdf = (*it).mData.mSumPdf;

                        // mark this entry as processed to avoid double counting
                        (*it).mData.mSumPdf = -aSumPdf;
                }

#if 0
                const float diff = bSumPdf - aSumPdf;

                if (diff > 0.0f) {
                        pvsEnlargement += diff;
                } else {
                        pvsReduction += -diff;
                }
#else
                if (!entryFound)
                        pvsEnlargement += 1.0f;
#endif
        }

        for (it = mEntries.begin(); it != mEntries.end(); ++ it) 
        {
                float aSumPdf = (*it).mData.mSumPdf;
                float bSumPdf = 0.0f;
                if (aSumPdf < 0.0f) {
                
                        // this entry was already accounted for!
                        // just revert it back
                        (*it).mData.mSumPdf = -aSumPdf;
                } else {
                        vector<PvsEntry<T, S> >::iterator oit;
                
                        const bool entryFound = b.Find((*it).mObject, oit);
                                                
                        if (entryFound) {
                                bSumPdf = (*oit).mData.mSumPdf;
                        }
#if 0
                        const float diff = bSumPdf - aSumPdf;

                        if (diff > 0.0f) {
                                pvsEnlargement += diff;
                        } else {
                                pvsReduction += -diff;
                        }

#else
                        if (!entryFound) 
                                pvsReduction += 1.0f;
#endif
                }
        }
}


template <typename T, typename S>
int Pvs<T, S>::Diff(const Pvs<T, S> &b)
{
        int dif = 0;

        std::vector<PvsEntry<T, S> >::const_iterator it;

        for (it = b.mEntries.begin(); it != b.mEntries.end(); ++ it)
        {
                vector<PvsEntry<T, S> >::iterator bit;
                const bool entryFound = Find((*it).first, bit);

                if (!entryFound) ++ dif;
        }

        return dif;
}


template <typename T, typename S> 
void Pvs<T, S>::MergeInPlace(const Pvs<T, S> &a)
{
        // early exit
        if (a.Empty())
        {
                return;
        }
        else if (Empty())
        {
                mEntries.reserve(a.GetSize());
                mEntries = a.mEntries;
                mSamples = a.mSamples;
                return;
        }

        ObjectPvs interPvs;
        
        Merge(interPvs, *this, a);
        
        mEntries.reserve(interPvs.GetSize());
        mEntries = interPvs.mEntries;
        mSamples = interPvs.mSamples;
}


template <typename T, typename S>
void Pvs<T, S>::Merge(Pvs<T, S> &mergedPvs, const Pvs<T, S> &a, const Pvs<T, S> &b)
{
        std::vector<PvsEntry<T, S> >::const_iterator ait = a.mEntries.begin(), ait_end = a.mEntries.end();
        std::vector<PvsEntry<T, S> >::const_iterator bit = b.mEntries.begin(), bit_end = b.mEntries.end();
        
        Merge(mergedPvs, 
                  ait, ait_end,
                  bit, bit_end,
                  a.mSamples,
                  b.mSamples);
}


template <typename T, typename S>
void Pvs<T, S>::Merge(Pvs<T, S> &mergedPvs, 
                                          const typename std::vector<PvsEntry<T, S> >::const_iterator &aBegin,
                                          const typename std::vector<PvsEntry<T, S> >::const_iterator &aEnd,
                                          const typename std::vector<PvsEntry<T, S> >::const_iterator &bBegin,
                                          const typename std::vector<PvsEntry<T, S> >::const_iterator &bEnd,
                                          const int aSamples, 
                                          const int bSamples)
{
        std::vector<PvsEntry<T, S> >::const_iterator ait = aBegin;
        std::vector<PvsEntry<T, S> >::const_iterator bit = bBegin;
        
        for (; (ait != aEnd); ++ ait)
        {
                Intersectable *aObj = (*ait).mObject;
                Intersectable *bObj = NULL;
                //Intersectable *bObjOld = NULL;
        
                const PvsEntry<T, S> &aEntry = (*ait);

                for (; (bit != bEnd) && ((*bit).mObject <= (*ait).mObject); ++ bit)
                {
                        bObj = (*bit).mObject;

                        // object found => add up probabilities
                        if (bObj == aEntry.mObject)
                        {
                                PvsData newData(aEntry.mData.mSumPdf + (*bit).mData.mSumPdf);
                                PvsEntry<T, S> entry(bObj, newData);
                                mergedPvs.mEntries.push_back(entry);
                        }
                        else
                        {
                                mergedPvs.mEntries.push_back(*bit);
                        }
                        
                        //bObjOld = bObj;
                }

                // only push back if objects different 
                // (equal case is handled by second loop)
                if (aObj != bObj)
                {
                        mergedPvs.mEntries.push_back(*ait);
                }
        }

        // add the rest
        for (; (bit != bEnd); ++ bit)
        {
                mergedPvs.mEntries.push_back(*bit);
        }

        mergedPvs.mSamples = aSamples + bSamples;
}


template <typename T, typename S> void Pvs<T, S>::Clear(const bool trim = true)
{
        mEntries.clear();
        mSamples = 0;
        mLastSorted = 0;

        if (trim)
        {
                vector<PvsEntry<T,S> >().swap(mEntries);
        }
}


template <typename T, typename S> void Pvs<T, S>::Trim()
{
        vector<PvsEntry<T,S> >(mEntries).swap(mEntries);
}


template <typename T, typename S> 
bool Pvs<T, S>::Find(T sample,
                                         typename vector<PvsEntry<T, S> >::iterator &it,
                                         const bool checkDirty)
{
  PvsEntry<T, S> dummy(sample, PvsData());
  mQueriesSinceSort++;
  
  // only check clean part
  vector<PvsEntry<T, S> >::iterator sorted_end = mEntries.begin() + mLastSorted;
  
  // binary search
  it = lower_bound(mEntries.begin(), sorted_end, dummy);
  
  if ((it != mEntries.end()) && ((*it).mObject == sample))
        //  if (it != sorted_end)
        return true;
  
  // sample not found yet => search further in the unsorted part
  if (checkDirty) {
        
        for (it = sorted_end; (it != mEntries.end()) && ((*it).mObject != sample); ++ it) ;
        
        if (it != mEntries.end())
          return true;
  }
  
  return false;
}


template <typename T, typename S>
void Pvs<T, S>::GetData(const int index, T &entry, S &data)
{
        std::vector<PvsEntry<T, S> >::iterator i = mEntries.begin();
        for (int k = 0; k != index && i != mEntries.end(); ++ i, ++ k);

        entry = (*i).first;
        data = (*i).second;
}


template <typename T, typename S>
float Pvs<T, S>::AddSample(T sample, const float pdf)
{
        ++ mSamples;
        
        vector<PvsEntry<T, S> >::iterator it;
        const bool entryFound = Find(sample, it);               

        if (entryFound)
        {       
                S &data = (*it).mData;
                data.mSumPdf += pdf;
                return data.mSumPdf;
        }
        else 
          {
                PvsEntry<T, S> entry(sample, pdf);
                mEntries.insert(it, entry);
                ++ mLastSorted;
                return pdf;
          }
}


template <typename T, typename S>
void Pvs<T, S>::AddSampleDirty(T sample, const float pdf)
{
        ++ mSamples;
        mEntries.push_back(PvsEntry<T, S>(sample, pdf));
}
                                         

template <typename T, typename S>
typename vector< PvsEntry<T, S> >::iterator Pvs<T, S>::AddSample2(T sample, 
                                                                                                                                  const float pdf)
{
        ++ mSamples;
        
        vector<PvsEntry<T, S> >::iterator it;
        const bool entryFound == Find(sample, it);

        if (entryFound)
        {
                S &data = (*it).second;
                data->mSumPdf += pdf;
        }
        else 
        {
                PvsEntry<T, S> entry(sample, pdf);
                mEntries.insert(it, entry);
                ++ mLastSorted;
        }

        return it;
}


/** Adds sample dirty (on the end of the vector) but
        first checks if sample is already in clean part of the pvs.
*/
template <typename T, typename S> 
bool Pvs<T, S>::AddSampleDirtyCheck(T sample,
                                                                        const float pdf)
                                                                        //,float &contribution)
{
        ++ mSamples;

        vector<PvsEntry<T, S> >::iterator it;
        bool entryFound = Find(sample, it);

        if (entryFound) {
          S &data = (*it).mData;
          
          data.mSumPdf += pdf;
          //contribution = pdf / data.mSumPdf;
          
          return false;
        }
        else {
          AddSampleDirty(sample, pdf);
          //contribution = 1.0f;
          return true;
        }
}


template <typename T, typename S>
bool Pvs<T, S>::GetSampleContribution(T sample,
                                                                          const float pdf,
                                                                          float &contribution) 
{
        vector<PvsEntry<T, S> >::iterator it;
        const bool entryFound = Find(sample, it);

        if (entryFound)  
        {
                S &data = (*it).mData;
                contribution = pdf / (data.mSumPdf + pdf);
                return false;
        }
        else 
        {
                contribution = 1.0f;
                return true;
        }
}


template <typename T, typename S>
bool Pvs<T, S>::RemoveSample(T sample, const float pdf)
{
        -- mSamples;
        
        vector<PvsEntry<T, S> >::iterator it;
        const bool entryFound = Find(sample, it);

        if (!entryFound)
                return false;

        S &data = (*it).mData;

        data.mSumPdf -= pdf;

        if (data.mSumPdf <= 0.0f)
        {
                mEntries.erase(it);
                -- mLastSorted; // wrong if sample was in tail!!
        }

        return true;
}


template <typename T, typename S>
int Pvs<T, S>::SubtractPvs(const Pvs<T, S> &pvs)
{
        const int samples = mSamples - pvs.mSamples;

        std::vector<PvsEntry<T, S> >::
                const_iterator it, it_end = pvs.mEntries.end();

        // output PVS of view cell
        for (it = pvs.mEntries.begin(); it != it_end; ++ it) 
                RemoveSample((*it).mObject, (*it).mData.mSumPdf);

        mSamples = samples;

        return GetSize();
}


template <typename T, typename S>
void Pvs<T, S>::CollectEntries(std::vector<T> &entries)
{
        std::vector<PvsEntry<T, S> >::
                const_iterator it, it_end = mEntries.end();

        // output PVS of view cell
        for (it = mEntries.begin(); it != it_end; ++ it) 
                entries.push_back((*it)->first);
}


template <typename T, typename S>
void Pvs<T, S>::NormalizeMaximum()
{
        std::vector<PvsEntry<T, S> >::
                const_iterator it, it_end = mEntries.end();

        float maxPdfSum = -1.0f;

        // output PVS of view cell
        for (it = mEntries.begin(); it != it_end; ++ it) {
                float sum = (*it)->second.sumPdf;
                if (sum > maxSum)
                        maxSum = sum;
        }

        maxSum = 1.0f / maxSum;

        for (it = mEntries.begin(); it != it_end; ++ it) {
                (*it)->second.sumPdf *= maxSum;
        }

}


template <typename T, typename S>
float Pvs<T, S>::GetEntrySize()
{
        return (float)(sizeof(T) + sizeof(S)) / float(1024 * 1024);
}


template <typename T, typename S>
int Pvs<T, S>::GetEntrySizeByte()
{
        return sizeof(T) + sizeof(S);
}


template <typename T, typename S>
float Pvs<T, S>::GetPvsHomogenity(Pvs<T, S> &pvs) 
{
        float pvsReduction, pvsEnlargement;

        ComputeContinuousPvsDifference(pvs,     pvsReduction, pvsEnlargement);

        return pvsReduction + pvsEnlargement;
}


template <typename T, typename S>
typename PvsIterator<T, S> Pvs<T, S>::GetIterator() const
{
        PvsIterator<T, S> pit(mEntries.begin(), mEntries.end());

        return pit;
}


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

/** Class instantiating the Pvs template for kd tree nodes.
*/
class KdPvs: public Pvs<KdNode *, PvsData>
{
public:
        int Compress();
};


////////////
//-- typedefs

typedef PvsEntry<Intersectable *, PvsData> ObjectPvsEntry;
typedef std::vector<ObjectPvsEntry> ObjectPvsEntries;
typedef Pvs<ViewCell *, MailablePvsData> ViewCellPvs;
typedef PvsIterator<Intersectable *, PvsData> ObjectPvsIterator;


class ObjectPvs: public Pvs<Intersectable *, PvsData>
{
public:
        /** Counts object int the pvs. Different to method "GetSize", not
                only the raw container size is returned,
                but the individual contributions of the entries are summed up.
        */
        float EvalPvsCost() const;

        friend ostream &operator<<(ostream &s, const ObjectPvs &p) 
        {
                ObjectPvsIterator pit = p.GetIterator();

                while (pit.HasMoreEntries())
                {               
                        const ObjectPvsEntry &entry = pit.Next();
                        Intersectable *obj = entry.mObject;

                        cout << obj << " ";
                }
                
                return s;
        }
};



}

#endif