source: trunk/VUT/GtpVisibilityPreprocessor/src/ViewCellBsp.cpp @ 294

#include "Plane3.h"
#include "ViewCellBsp.h"
#include "Mesh.h"
#include "common.h"
#include "ViewCell.h"
#include "Environment.h"
#include "Polygon3.h"
#include "Ray.h"
#include "AxisAlignedBox3.h"
#include <stack>
#include <time.h>
#include <iomanip>
#include "Exporter.h"

int BspTree::sTermMaxPolygons = 10;
int BspTree::sTermMaxDepth = 20;
int BspTree::sMaxCandidates = 10;
int BspTree::sSplitPlaneStrategy = NEXT_POLYGON; 
int BspTree::sConstructionMethod = VIEW_CELLS;

/** Evaluates split plane classification with respect to the plane's 
        contribution for a balanced tree.
*/
float BspTree::sLeastSplitsTable[] = {0, 0, 1, 0};
/** Evaluates split plane classification with respect to the plane's 
        contribution for a minimum number splits in the tree.
*/
float BspTree::sBalancedTreeTable[] = {-1, 1, 0, 0};

//int counter = 0;

/****************************************************************/
/*                  class BspNode implementation                */
/****************************************************************/

BspNode::BspNode(): mParent(NULL), mPolygons(NULL)//,mViewCellIdx(0)
{}

BspNode::BspNode(BspInterior *parent): mParent(parent), mPolygons(NULL)//,mViewCellIdx(0)
{}

BspNode::~BspNode()
{
        if (mPolygons)
        {
                CLEAR_CONTAINER(*mPolygons);
                DEL_PTR(mPolygons);
        }
}

bool BspNode::IsRoot() const 
{
        return mParent == NULL;
}

BspInterior *BspNode::GetParent() 
{ 
        return mParent; 
}

void BspNode::SetParent(BspInterior *parent)
{
        mParent = parent;
}

PolygonContainer *BspNode::GetPolygons()
{
        if (!mPolygons)
                mPolygons = new PolygonContainer();

        return mPolygons;
}

void BspNode::ProcessPolygons(PolygonContainer *polys, bool storePolys)
{
        if (storePolys)
        {
                while (!polys->empty())
                {
                        GetPolygons()->push_back(polys->back());
                        polys->pop_back();
                }
        }
        else CLEAR_CONTAINER(*polys);
}


/****************************************************************/
/*              class BspInterior implementation                */
/****************************************************************/


BspInterior::BspInterior(const Plane3 &plane): 
mPlane(plane), mFront(NULL), mBack(NULL)
{}

bool BspInterior::IsLeaf() const
{ 
        return false; 
}

BspNode *BspInterior::GetBack() 
{
        return mBack;
}

BspNode *BspInterior::GetFront() 
{
        return mFront;
}

Plane3 *BspInterior::GetPlane()
{
        return &mPlane;
}

void BspInterior::ReplaceChildLink(BspNode *oldChild, BspNode *newChild) 
{
        if (mBack == oldChild)
                mBack = newChild;
        else
                mFront = newChild;
}

void BspInterior::SetupChildLinks(BspNode *b, BspNode *f) 
{
    mBack = b;
    mFront = f;
}

void BspInterior::ProcessPolygon(Polygon3 **poly, const bool storePolys)
{
        if (storePolys) 
                GetPolygons()->push_back(*poly);
        else
                DEL_PTR(*poly);
}

void BspInterior::SplitPolygons(PolygonContainer *polys, 
                                                                PolygonContainer *frontPolys, 
                                                                PolygonContainer *backPolys, 
                                                                PolygonContainer *coincident,
                                                                int &splits, 
                                                                bool storePolys)
{
        Polygon3 *splitPoly = NULL;
#ifdef _Debug
        Debug << "splitting polygons of node " << this << " with plane " << mPlane << endl;
#endif
        while (!polys->empty())
        {
                Polygon3 *poly = polys->back();
                polys->pop_back();

                //Debug << "New polygon with plane: " << poly->GetSupportingPlane() << "\n";

                // get polygon classification
                int classification = poly->ClassifyPlane(mPlane);

                Polygon3 *front_piece = NULL;
                Polygon3 *back_piece = NULL;
        
                switch (classification)
                {
                        case Polygon3::COINCIDENT:
                                //Debug << "coincident" << endl;        
                                coincident->push_back(poly);
                                break;                  
                        case Polygon3::FRONT_SIDE:      
                                //Debug << "front" << endl;
                                frontPolys->push_back(poly);
                                break;
                        case Polygon3::BACK_SIDE:
                                //Debug << "back" << endl;
                                backPolys->push_back(poly);
                                break;
                        case Polygon3::SPLIT:
                                front_piece = new Polygon3(poly->mParent);
                                back_piece = new Polygon3(poly->mParent);

                                //-- split polygon into front and back part
                                poly->Split(&mPlane, front_piece, back_piece);

                                ++ splits; // increase number of splits
                                // check if polygon still valid 
                                if (front_piece->mVertices.size() >= 3)
                                        frontPolys->push_back(front_piece);
                                else
                                        DEL_PTR(front_piece);
                                // check if polygon still valid
                                if (back_piece->mVertices.size() >= 3)
                                        backPolys->push_back(back_piece);
                                else                            
                                        DEL_PTR(back_piece);
                                
#ifdef _DEBUG
                                Debug << "split " << *poly << endl << *front_piece << endl << *back_piece << endl;
#endif
                                ProcessPolygon(&poly, storePolys);
                                
                                break;
                        default:
                Debug << "SHOULD NEVER COME HERE\n";
                                break;
                }
        }
}

/****************************************************************/
/*                  class BspLeaf implementation                */
/****************************************************************/
BspLeaf::BspLeaf(): mViewCell(NULL)
{
}

BspLeaf::BspLeaf(ViewCell *viewCell): mViewCell(viewCell)
{
}

BspLeaf::BspLeaf(BspInterior *parent): BspNode(parent), mViewCell(NULL)
{}

BspLeaf::BspLeaf(BspInterior *parent, ViewCell *viewCell): 
BspNode(parent), mViewCell(viewCell)
{
}
ViewCell *BspLeaf::GetViewCell()
{
        return mViewCell;
}

void BspLeaf::SetViewCell(ViewCell *viewCell)
{
        mViewCell = viewCell;
}

bool BspLeaf::IsLeaf() const 
{ 
        return true; 
}

/****************************************************************/
/*                  class BspTree implementation                */
/****************************************************************/

BspTree::BspTree(): 
mTermMaxPolygons(0), 
mTermMaxDepth(0), 
mRoot(NULL), 
mVerticalAxis(Vector3(0, 0, 1)),
//mStorePolys(true)
mStorePolys(false)
{
        Randomize(); // initialise random generator for heuristics
}
 
const BspTreeStatistics &BspTree::GetStatistics() const 
{
        return mStat;
}

void BspTreeStatistics::Print(ostream &app) const
{
        app << "===== BspTree statistics ===============\n";

        app << setprecision(4);

        app << "#N_RAYS Number of rays )\n"
                << rays << endl;
        app << "#N_DOMAINS  ( Number of query domains )\n"
                << queryDomains <<endl;

        app << "#N_NODES ( Number of nodes )\n" << nodes << "\n";

        app << "#N_INTERIORS ( Number of interior nodes )\n" << Interior() << "\n";

        app << "#N_LEAVES ( Number of leaves )\n" << Leaves() << "\n";

        app << "#N_SPLITS ( Number of splits )\n" << splits << "\n";

        app << "#N_RAYREFS ( Number of rayRefs )\n" <<
        rayRefs << "\n";

        app << "#N_RAYRAYREFS  ( Number of rayRefs / ray )\n" <<
        rayRefs/(double)rays << "\n";

        app << "#N_LEAFRAYREFS  ( Number of rayRefs / leaf )\n" <<
        rayRefs/(double)Leaves() << "\n";

        app << "#N_MAXOBJECTREFS  ( Max number of rayRefs / leaf )\n" <<
        maxObjectRefs << "\n";

        app << "#N_NONEMPTYRAYREFS  ( Number of rayRefs in nonEmpty leaves / non empty leaf )\n" <<
        rayRefsNonZeroQuery/(double)(Leaves() - zeroQueryNodes) << "\n";

        app << "#N_LEAFDOMAINREFS  ( Number of query domain Refs / leaf )\n" <<
        objectRefs/(double)Leaves() << "\n";

        app << "#N_PEMPTYLEAVES  ( Percentage of leaves with zero query domains )\n"<<
        zeroQueryNodes*100/(double)Leaves() << endl;

        app << "#N_PMAXDEPTHLEAVES ( Percentage of leaves at maxdepth )\n"<<
        maxDepthNodes * 100 / (double)Leaves() << endl;

        app << "#N_PMAXDEPTH ( Maximal reached depth )\n" << maxDepth << endl;

        app << "#N_PMINDEPTH ( Minimal reached depth )\n" << minDepth << endl;

        app << "#AVGDEPTH ( average depth )\n" << AvgDepth() << endl;

        app << "#N_ADDED_RAYREFS  ( Number of dynamically added ray references )\n"<<
        addedRayRefs << endl;

        app << "#N_REMOVED_RAYREFS  ( Number of dynamically removed ray references )\n" <<
        removedRayRefs << endl;

        app << "#N_INPUT_POLYGONS (number of input polygons )\n" <<
                polys << endl;

        app << "#N_ROUTPUT_INPUT_POLYGONS ( ratio polygons after subdivision / input polygons )\n" <<
                 (polys + splits) / (double)polys << endl;
        
        app << "===== END OF BspTree statistics ==========\n";
}

BspTree::~BspTree()
{
        std::stack<BspNode *> tStack;

        tStack.push(mRoot);

        while (!tStack.empty())
        {
                BspNode *node = tStack.top();

            tStack.pop();
        
                if (!node->IsLeaf())
                {
                        BspInterior *interior = dynamic_cast<BspInterior *>(node);

                        // push the children on the stack (there are always two children)
                        tStack.push(interior->GetBack());
                        tStack.push(interior->GetFront());
                }

                DEL_PTR(node);
        }
}

void BspTree::InsertViewCell(ViewCell *viewCell)
{
        PolygonContainer *polys = new PolygonContainer();

        // extract polygons that guide the split process
        mStat.polys += AddMesh2Polygons(viewCell->GetMesh(), *polys);
        mBox.Include(viewCell->GetBox()); // add to BSP aabb

        InsertPolygons(polys);
}

void BspTree::InsertPolygons(PolygonContainer *polys, ViewCellContainer *viewCells)
{       
        std::stack<BspTraversalData> tStack;
                
        // traverse tree or create new one
        BspNode *firstNode = mRoot ? mRoot : new BspLeaf();

        tStack.push(BspTraversalData(firstNode, polys, 0, NULL));

        while (!tStack.empty())
        {
                // filter polygons donw the tree
                BspTraversalData tData = tStack.top();
            tStack.pop();
                        
                if (!tData.mNode->IsLeaf())
                {
                        BspInterior *interior = dynamic_cast<BspInterior *>(tData.mNode);

                        //-- filter view cell polygons down the tree until a leaf is reached
                        if ((int)tData.mPolygons->size() > 0)
                        {
                                PolygonContainer *frontPolys = new PolygonContainer();
                                PolygonContainer *backPolys = new PolygonContainer();
                                PolygonContainer coincident;

                                int splits = 0;
                
                                // split viecell polygons with respect to split plane
                                interior->SplitPolygons(tData.mPolygons, 
                                                                                frontPolys, 
                                                                                backPolys,
                                                                                &coincident,
                                                                                splits, 
                                                                                mStorePolys);
                                
                                // get view cell associated with the split polygon
                                ViewCell *viewCell = (coincident.size() > 0) ? 
                                        dynamic_cast<ViewCell *>(coincident.front()->mParent) : NULL;
                                interior->ProcessPolygons(&coincident, mStorePolys);

                                //Debug << "split node on level " << tData.mDepth << " bk: " << backPolys->size() << " frnt: " << frontPolys->size() << endl;
                                mStat.splits += splits;

                                // push the children on the stack
                                tStack.push(BspTraversalData(interior->GetFront(), frontPolys, tData.mDepth + 1, NULL));
                                tStack.push(BspTraversalData(interior->GetBack(), backPolys, tData.mDepth + 1, viewCell));
                        }

                        // cleanup
                        DEL_PTR(tData.mPolygons);
                }
                else // reached leaf => subdivide current viewcell
                {
                        if (tData.mPolygons->size() > 0)
                                Debug << "Subdividing further: polygon size: " << (int)tData.mPolygons->size() << ", view cell: " << tData.mViewCell << endl;

                        BspNode *root = Subdivide(tStack, tData, viewCells);            

                        if (!mRoot) // tree empty => new root
                                mRoot = root;
                }
        }
}

void BspTree::InitTree(int maxPolygons, int maxDepth)
{
        mTermMaxPolygons = maxPolygons;
        mTermMaxDepth = maxDepth;
        mStat.nodes = 1;
        
        mBox.Initialize();      // initialise bsp tree bounding box
}



int BspTree::AddMesh2Polygons(Mesh *mesh, PolygonContainer &polys, Intersectable *parent)
{
        FaceContainer::const_iterator fi;
        int polysNum = 0;

        // copy the face data to polygons
        for (fi = mesh->mFaces.begin(); fi != mesh->mFaces.end(); ++ fi)
        {
                Polygon3 *poly = new Polygon3((*fi), mesh);
                poly->mParent = parent; // set parent intersectable
                polys.push_back(poly);

                if (!poly->CheckValid())
                        Debug << "Input polygon not valid: " << *poly << endl;

                ++ polysNum;
        }
        return polysNum;
}

int BspTree::Copy2PolygonSoup(const ViewCellContainer &viewCells, PolygonContainer &polys, int maxObjects)
{
        int limit = (maxObjects > 0) ? Min((int)viewCells.size(), maxObjects) : (int)viewCells.size();
  
        for (int i = 0; i < limit; ++i)
        {//if ((i == 12) ||(i==14))
                if (viewCells[i]->GetMesh()) // copy the mesh data to polygons
                {
                        mBox.Include(viewCells[i]->GetBox()); // add to BSP tree aabb
                        AddMesh2Polygons(viewCells[i]->GetMesh(), polys, viewCells[i]);
                }
        }

        return (int)polys.size();
}

int BspTree::Copy2PolygonSoup(const ObjectContainer &objects, PolygonContainer &polys, int maxObjects)
{
        int limit = (maxObjects > 0) ? Min((int)objects.size(), maxObjects) : (int)objects.size();
  
        for (int i = 0; i < limit; ++i)
        {
                Intersectable *object = objects[i];//*it;
                Mesh *mesh = NULL;

                switch (object->Type()) // extract the meshes
                {
                case Intersectable::MESH_INSTANCE:
                        mesh = dynamic_cast<MeshInstance *>(object)->GetMesh();
                        break;
                case Intersectable::VIEWCELL:
                        mesh = dynamic_cast<ViewCell *>(object)->GetMesh();
                        break;
                        // TODO: handle transformed mesh instances
                default:
                        break;
                }
                
        if (mesh) // copy the mesh data to polygons
                {
                        mBox.Include(object->GetBox()); // add to BSP tree aabb
                        AddMesh2Polygons(mesh, polys);
                }
        }

        return (int)polys.size();
}

void BspTree::Construct(const ViewCellContainer &viewCells)
{
        InitTree(sTermMaxPolygons, sTermMaxDepth);

        // copy view cell meshes into one big polygon soup
        PolygonContainer *polys = new PolygonContainer();
        mStat.polys = Copy2PolygonSoup(viewCells, *polys);

        // construct tree from viewcell polygons
        Construct(polys);
        //Export("bsp.x3d");
}


void BspTree::Construct(const ObjectContainer &objects, ViewCellContainer *viewCells)
{
        // take termination criteria from globals
        InitTree(sTermMaxPolygons, sTermMaxDepth);
        
        PolygonContainer *polys = new PolygonContainer();
        
        // copy mesh instance polygons into one big polygon soup
        mStat.polys = Copy2PolygonSoup(objects, *polys);

        // construct tree from polygon soup
        Construct(polys, viewCells);
}

void BspTree::Construct(const RayContainer &rays, ViewCellContainer *viewCells)
{
        // TODO
}

void BspTree::Construct(PolygonContainer *polys, ViewCellContainer *viewCells)
{
        std::stack<BspTraversalData> tStack;
        
        BspTraversalData tData(new BspLeaf(), polys, 0, NULL);

        tStack.push(tData);

        long startTime = GetTime();
        Debug << "**** Contructing tree using objects ****\n";
        while (!tStack.empty()) 
        {
                tData = tStack.top();
            tStack.pop();

                // subdivide leaf node
                BspNode *root = Subdivide(tStack, tData, viewCells);

                // empty tree => new root corresponding to unbounded space
                if (!mRoot) 
                        mRoot = root;
        }

        Debug << "**** Finished tree construction ****\n";
        Debug << "BSP tree contruction time: " << TimeDiff(startTime, GetTime())*1e-3 << "s" << endl;
}


BspNode *BspTree::Subdivide(BspTraversalStack &tStack, BspTraversalData &tData, 
                                                        ViewCellContainer *viewCells)
{
        //-- terminate traversal  
        if ((tData.mPolygons->size() <= mTermMaxPolygons) || (tData.mDepth >= mTermMaxDepth))
        {
#ifdef _DEBUG
                Debug << "subdivision terminated at depth " << tData.mDepth << ", #polys: " << (int)tData.mPolygons->size() << endl;
#endif

                EvaluateLeafStats(tData);

                BspLeaf *leaf = dynamic_cast<BspLeaf *>(tData.mNode);

                //-- new viewcells are generated and added to each leaf
                if (viewCells)
                {
                        ViewCell *viewCell = new ViewCell();
                        leaf->SetViewCell(viewCell);
                        viewCells->push_back(viewCell);
                        // Debug << "creating new viewcell" << endl;
                }
                //-- add viewcell stored in split polygon
                else if (tData.mViewCell)
                {
                        if (leaf->GetViewCell())
                                Debug << "ERROR: leaf already has view cell " << endl;//leaf->mViewCellIdx << endl;

                        //leaf->mViewCellIdx = counter; Debug << "insert view cell " << tData.mViewCell << endl;
                        leaf->SetViewCell(dynamic_cast<ViewCell *>(tData.mViewCell));
                }
        
                // remaining polygons are discarded or added to node
                tData.mNode->ProcessPolygons(tData.mPolygons, mStorePolys);
                DEL_PTR(tData.mPolygons);

                return tData.mNode;
        }

        //-- continue subdivision
        PolygonContainer *backPolys = new PolygonContainer();
        PolygonContainer *frontPolys = new PolygonContainer();
        PolygonContainer coincident;
        
        // create new interior node and two leaf nodes
        BspInterior *interior = SubdivideNode(dynamic_cast<BspLeaf *>(tData.mNode),
                                                                                  tData.mPolygons,
                                                                                  frontPolys,
                                                                                  backPolys, 
                                                                                  &coincident);

        // view cell associated with the first split polygon
        ViewCell *viewCell = (coincident.size() > 0) ? 
                                        dynamic_cast<ViewCell *>(coincident.front()->mParent) : NULL;
        interior->ProcessPolygons(&coincident, mStorePolys);

        // push the children on the stack
        // split polygon is only needed in the back leaf
        tStack.push(BspTraversalData(interior->GetFront(), frontPolys, tData.mDepth + 1, NULL));
        tStack.push(BspTraversalData(interior->GetBack(), backPolys, tData.mDepth + 1, viewCell));

        // cleanup
        DEL_PTR(tData.mNode);
        DEL_PTR(tData.mPolygons);

        return interior;
}


BspInterior *BspTree::SubdivideNode(BspLeaf *leaf, 
                                                                        PolygonContainer *polys, 
                                                                        PolygonContainer *frontPolys,
                                                                        PolygonContainer *backPolys, 
                                                                        PolygonContainer *coincident)
{
        mStat.nodes += 2;

        // add the new nodes to the tree + select subdivision plane
        BspInterior *interior = new BspInterior(SelectPlane(polys)); 

#ifdef _DEBUG
        Debug << interior << endl;
#endif

        // split polygon according to current plane
        int splits = 0;
        
        interior->SplitPolygons(polys, frontPolys, backPolys, coincident, splits, mStorePolys);
        
        mStat.splits += splits;

        BspInterior *parent = leaf->GetParent();

        // replace a link from node's parent
        if (parent)
        {
                parent->ReplaceChildLink(leaf, interior);
                interior->SetParent(parent);
        }

        // and setup child links
        interior->SetupChildLinks(new BspLeaf(interior), new BspLeaf(interior));
        
        return interior;
}

Plane3 BspTree::SelectPlane(PolygonContainer *polys)  const
{
        if (polys->size() == 0)
        {
                Debug << "Warning: No split candidate available\n";
                return Plane3();
        }

        // simple strategy: just take next polygon
        if (sSplitPlaneStrategy & NEXT_POLYGON)
        {
                return polys->front()->GetSupportingPlane();
        }
        
    if (sSplitPlaneStrategy & VERTICAL_AXIS)
        {
                const float dot_thres = 0.999;
                PolygonContainer::const_iterator it, it_end = polys->end();
                
                for (it = polys->begin(); it != it_end; ++ it)
                {
                        if (DotProd((*it)->GetSupportingPlane().mNormal, mVerticalAxis) > dot_thres)
                                return (*it)->GetSupportingPlane();
                }
        }
        // use heuristics to find appropriate plane
        return SelectPlaneHeuristics(polys, sMaxCandidates);
}

Plane3 BspTree::SelectPlaneHeuristics(PolygonContainer *polygons, int maxTests) const
{
        float lowestCost = MAX_FLOAT;
        int bestPlaneIdx = 0;
        
        int limit = Min((int)polygons->size(), maxTests);

        for (int i = 0; i < limit; ++ i)
        {
                int candidateIdx = Random((int)polygons->size()); // TODO: avoid testing same plane 2 times
                Plane3 candidatePlane = (*polygons)[candidateIdx]->GetSupportingPlane();
                
                // evaluate current candidate
                float candidateCost = EvalSplitPlane(polygons, candidatePlane);
                        
                if (candidateCost < lowestCost)
                {
                        bestPlaneIdx = candidateIdx;
                        lowestCost = candidateCost;
                }
        }
        //Debug << "Plane lowest cost: " << lowestCost << endl;
        
        return (*polygons)[bestPlaneIdx]->GetSupportingPlane();
}

float BspTree::EvalSplitPlane(PolygonContainer *polygons, const Plane3 &candidatePlane) const
{
        PolygonContainer::const_iterator it;

        float sumBalanced = 0, sumLeastSplits = 0;

        for (it = polygons->begin(); it != polygons->end(); ++ it)
        {
                int classification = (*it)->ClassifyPlane(candidatePlane);
                
                if (sSplitPlaneStrategy & BALANCED_TREE)
                {
                        sumBalanced += sBalancedTreeTable[classification];
                }
                
                if (sSplitPlaneStrategy & LEAST_SPLITS)
                {
                        sumLeastSplits += sLeastSplitsTable[classification];
                }
        }

        // return linear combination of both sums
        return fabs(sumBalanced) + fabs(sumLeastSplits);
}

void BspTree::ParseEnvironment()
{
        environment->GetIntValue("BspTree.Termination.maxDepth", sTermMaxDepth);
        environment->GetIntValue("BspTree.Termination.maxPolygons", sTermMaxPolygons);
        environment->GetIntValue("BspTree.maxCandidates", sMaxCandidates);
        environment->GetIntValue("BspTree.splitPlaneStrategy", sSplitPlaneStrategy);

        Debug << "BSP max depth: " << sTermMaxDepth << endl;
        Debug << "BSP max polys: " << sTermMaxPolygons << endl;
        Debug << "BSP max candidates: " << sMaxCandidates << endl;

        //-- parse BSP tree construction method
        char constructionMethodStr[60];
        
        environment->GetStringValue("BspTree.constructionMethod", constructionMethodStr);

        sConstructionMethod = BspTree::VIEW_CELLS;
        
        if (strcmp(constructionMethodStr, "viewCells") == 0)
                sConstructionMethod = BspTree::VIEW_CELLS;
        else if (strcmp(constructionMethodStr, "sceneGeometry") == 0)
                sConstructionMethod = BspTree::SCENE_GEOMETRY;
        else if (strcmp(constructionMethodStr, "rays") == 0)
                sConstructionMethod = BspTree::RAYS;
        else 
        {
                cerr << "Wrong bsp construction method " << constructionMethodStr << endl;
                exit(1);
    }

        Debug << "Construction method: " << constructionMethodStr << endl;
}

void BspTree::CollectLeaves(vector<BspLeaf *> &leaves)
{
        stack<BspNode *> nodeStack;
        nodeStack.push(mRoot);
 
        while (!nodeStack.empty()) 
        {
                BspNode *node = nodeStack.top();
    
                nodeStack.pop();
    
                if (node->IsLeaf()) 
                {
                        BspLeaf *leaf = (BspLeaf *)node;
                        
                        leaves.push_back(leaf);
                } else 
                {
                        BspInterior *interior = dynamic_cast<BspInterior *>(node);
                        nodeStack.push(interior->GetBack());
                        nodeStack.push(interior->GetFront());
                }
        }
}

int BspTree::CollectLeafPvs()
{
        int totalPvsSize = 0;
  
        stack<BspNode *> nodeStack;
  
        nodeStack.push(mRoot);
  
        while (!nodeStack.empty()) 
        {
                BspNode *node = nodeStack.top();
                
                nodeStack.pop();
                
                if (node->IsLeaf()) 
                {
                        BspLeaf *leaf = dynamic_cast<BspLeaf *>(node);

                        ViewCell *viewcell = leaf->GetViewCell();
                        
                        if (!viewcell->Mailed()) 
                        {
                                viewcell->Mail(); // what does mail mean?
                                        
                                // add this node to pvs of all nodes it can see
                                BspPvsMap::iterator ni; 
          
        /*                      for (ni = object->mBspPvs.mEntries.begin(); ni != object->mKdPvs.mEntries.end(); ni++) 
                                {
                                        BspNode *node = (*ni).first;
            
                                        // $$ JB TEMPORARY solution -> should add object PVS or explictly computed
                                        // BSP tree PVS
                                if (leaf->mBspPvs.AddNodeSample(node))
                                                totalPvsSize++;
                                }*/
                        }
                } else 
                {
                        // traverse tree
                        BspInterior *interior = (BspInterior *)node;
      
                        nodeStack.push(interior->GetFront());
                        nodeStack.push(interior->GetBack());
                }
        }

        return totalPvsSize;
}

AxisAlignedBox3 BspTree::GetBoundingBox() const
{
        return mBox;
}

BspNode *BspTree::GetRoot() const
{
        return mRoot;
}

bool BspTree::StorePolys() const
{
        return mStorePolys;
}

void BspTree::EvaluateLeafStats(const BspTraversalData &data)
{
        // the node became a leaf -> evaluate stats for leafs
        BspLeaf *leaf = dynamic_cast<BspLeaf *>(data.mNode);

        if (data.mDepth >= mTermMaxDepth)
        {
                ++ mStat.maxDepthNodes;
        }

        // store maximal and minimal depth
        if (data.mDepth > mStat.maxDepth)
                mStat.maxDepth = data.mDepth;
        if (data.mDepth < mStat.minDepth)
                mStat.minDepth = data.mDepth;

        // accumulate depth to compute average
        mStat.accumDepth += data.mDepth;

        if (leaf->mViewCell)
                ++ mStat.viewCellLeaves;

#ifdef _DEBUG
        Debug << "BSP Traversal data. Depth: " << data.mDepth << " (max: " << mTermMaxDepth << "), #polygons: " << 
          data.mPolygons->size() << " (max: " << mTermMaxPolygons << ")" << endl;
#endif
}

int BspTree::CastRay(Ray &ray)
{
        int hits = 0;
  
        stack<BspRayTraversalData> tStack;
  
        float maxt = 1e6;
        float mint = 0;

        Intersectable::NewMail();

        // test with tree bounding box
        if (!mBox.GetMinMaxT(ray, &mint, &maxt))
                return 0;

        if (mint < 0)
                mint = 0;
  
        maxt += Limits::Threshold;
  
        Vector3 entp = ray.Extrap(mint);
        Vector3 extp = ray.Extrap(maxt);
  
        BspNode *node = mRoot;
        BspNode *farChild;
        
        while (1)
        {
                if (!node->IsLeaf()) 
                {
                        BspInterior *in = (BspInterior *) node;
                        
                        Plane3 *splitPlane = in->GetPlane();

                        float t = 0;
                        bool coplanar = false;
                
                        int entSide = splitPlane->Side(entp);
                        int extSide = splitPlane->Side(extp);

                        Vector3 intersection;

                        if (entSide < 0)
                        {
                                node = in->GetBack();

                                if(extSide <= 0) 
                                        continue;
                                        
                                farChild = in->GetFront(); // plane splits ray

                        } else if (entSide > 0)
                        {
                                node = in->GetFront();

                                if (extSide >= 0)
                                        continue;

                                farChild = in->GetBack();        // plane splits ray                    
                        }
                        else // ray and plane are coincident // WHAT TO DO IN THIS CASE ?
                        {
                                node = in->GetFront();
                                continue;
                        }

                        //-- split

                        // push data for far child
                        tStack.push(BspRayTraversalData(farChild, extp, maxt));

                        // find intersection with plane between ray origin and exit point
                        extp = splitPlane->FindIntersection(ray.GetLoc(), extp, &maxt);

                } else // compute intersections with objects in leaf
                {
                        BspLeaf *leaf = dynamic_cast<BspLeaf *>(node);
                        //ray.leaves.push_back(leaf);
      // TODO
                        /*ObjectContainer::const_iterator mi;
                        for (mi = leaf->mObjects.begin(); mi != leaf->mObjects.end(); ++mi) 
                        {
                                Intersectable *object = *mi;
                                if (!object->Mailed()) 
                                {
                                        object->Mail();
                                        //ray.meshes.push_back(mesh);
                                        hits += object->CastRay(ray);
                                }
                        }*/

                        if (hits && ray.GetType() == Ray::LOCAL_RAY)
                                if (ray.intersections[0].mT <= maxt)
                                        break;
      
                        // get the next node from the stack
                        if (tStack.empty())
                                break;
      
                        entp = extp;
                        mint = maxt;
                        BspRayTraversalData &s  = tStack.top();

                        node = s.mNode;
                        extp = s.mExitPoint;
                        maxt = s.mMaxT;

                        tStack.pop();
                }
        }

        return hits;
}

bool BspTree::Export(const string filename)
{
        Exporter *exporter = Exporter::GetExporter(filename);

        if (exporter) 
        {
                exporter->ExportBspTree(*this);
                return true;
        }       

        return false;
}
//} // GtpVisibilityPreprocessor