/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2003 Robert Osfield 
 *
 * This library is open source and may be redistributed and/or modified under  
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 * OpenSceneGraph Public License for more details.
*/
#include <osg/Transform>
#include <osg/Projection>
#include <osg/Geode>
#include <osg/LOD>
#include <osg/Billboard>
#include <osg/LightSource>
#include <osg/ClipNode>
#include <osg/TexGenNode>
#include <osg/OccluderNode>
#include <osg/Notify>
#include <osg/TexEnv>
#include <osg/AlphaFunc>
#include <osg/LineSegment>
#include <osg/TriangleFunctor>
#include <osg/Geometry>

#include <osgUtil/CullVisitor>
#include <osgUtil/RenderToTextureStage>

#include <float.h>
#include <algorithm>

#include <osg/Timer>

using namespace osg;
using namespace osgUtil;

inline float MAX_F(float a, float b)
    { return a>b?a:b; }
inline int EQUAL_F(float a, float b)
    { return a == b || fabsf(a-b) <= MAX_F(fabsf(a),fabsf(b))*1e-3f; }


class PrintVisitor : public NodeVisitor
{

   public:
   
        PrintVisitor(std::ostream& out):
            NodeVisitor(NodeVisitor::TRAVERSE_ALL_CHILDREN),
            _out(out)
        {
            _indent = 0;
            _step = 4;
        }
        
        inline void moveIn() { _indent += _step; }
        inline void moveOut() { _indent -= _step; }
        inline void writeIndent() 
        {
            for(int i=0;i<_indent;++i) _out << " ";
        }
                
        virtual void apply(Node& node)
        {
            moveIn();
            writeIndent(); _out << node.className() <<std::endl;
            traverse(node);
            moveOut();
        }

        virtual void apply(Geode& node)         { apply((Node&)node); }
        virtual void apply(Billboard& node)     { apply((Geode&)node); }
        virtual void apply(LightSource& node)   { apply((Group&)node); }
        virtual void apply(ClipNode& node)      { apply((Group&)node); }
        
        virtual void apply(Group& node)         { apply((Node&)node); }
        virtual void apply(Transform& node)     { apply((Group&)node); }
        virtual void apply(Projection& node)    { apply((Group&)node); }
        virtual void apply(Switch& node)        { apply((Group&)node); }
        virtual void apply(LOD& node)           { apply((Group&)node); }
        virtual void apply(Impostor& node)      { apply((LOD&)node); }

   protected:
    
        std::ostream& _out;
        int _indent;
        int _step;
};

CullVisitor::CullVisitor():
    NodeVisitor(CULL_VISITOR,TRAVERSE_ACTIVE_CHILDREN),
    _currentRenderGraph(NULL),
    _currentRenderBin(NULL),
    _computed_znear(FLT_MAX),
    _computed_zfar(-FLT_MAX),
    _currentReuseRenderLeafIndex(0)
{
    _impostorSpriteManager = new ImpostorSpriteManager;
    // _nearFarRatio = 0.000005f;     
}


CullVisitor::~CullVisitor()
{
    reset();
}


void CullVisitor::reset()
{

    //
    // first unref all referenced objects and then empty the containers.
    //
    
    CullStack::reset();

    // reset the calculated near far planes.
    _computed_znear = FLT_MAX;
    _computed_zfar = -FLT_MAX;
    
    
    osg::Vec3 lookVector(0.0,0.0,-1.0);
    
    _bbCornerFar = (lookVector.x()>=0?1:0) |
                   (lookVector.y()>=0?2:0) |
                   (lookVector.z()>=0?4:0);

    _bbCornerNear = (~_bbCornerFar)&7;
    
    // reset the resuse lists.
    _currentReuseMatrixIndex = 0;
    _currentReuseRenderLeafIndex = 0;
    
    for(RenderLeafList::iterator itr=_reuseRenderLeafList.begin();
        itr!=_reuseRenderLeafList.end();
        ++itr)
    {
        (*itr)->reset();
    }
    
    if (_impostorSpriteManager.valid()) _impostorSpriteManager->reset();
    

    _nearPlaneCandidateMap.clear();
}

float CullVisitor::getDistanceToEyePoint(const Vec3& pos, bool withLODScale) const
{
    if (withLODScale) return (pos-getEyeLocal()).length()*getLODScale();
    else return (pos-getEyeLocal()).length();
}

inline CullVisitor::value_type distance(const osg::Vec3& coord,const osg::Matrix& matrix)
{

    //std::cout << "distance("<<coord<<", "<<matrix<<")"<<std::endl;

    return -((CullVisitor::value_type)coord[0]*(CullVisitor::value_type)matrix(0,2)+(CullVisitor::value_type)coord[1]*(CullVisitor::value_type)matrix(1,2)+(CullVisitor::value_type)coord[2]*(CullVisitor::value_type)matrix(2,2)+matrix(3,2));
}

float CullVisitor::getDistanceFromEyePoint(const osg::Vec3& pos, bool withLODScale) const
{
    const Matrix& matrix = *_modelviewStack.back();
    float dist = distance(pos,matrix);
    
    if (withLODScale) return dist*getLODScale();
    else return dist;
}

void CullVisitor::popProjectionMatrix()
{

    if (!_nearPlaneCandidateMap.empty())
    { 
    
        // osg::Timer_t start_t = osg::Timer::instance()->tick();
        
        // update near from defferred list of drawables
        unsigned int numTests = 0;
        for(DistanceMatrixDrawableMap::iterator itr=_nearPlaneCandidateMap.begin();
            itr!=_nearPlaneCandidateMap.end() && itr->first<_computed_znear;
            ++itr)
        {
            ++numTests;
            // osg::notify(osg::WARN)<<"testing computeNearestPointInFrustum with d_near = "<<itr->first<<std::endl;
            value_type d_near = computeNearestPointInFrustum(itr->second._matrix, itr->second._planes,*(itr->second._drawable));
            if (d_near<_computed_znear)
            {
                _computed_znear = d_near;
                // osg::notify(osg::WARN)<<"updating znear to "<<_computed_znear<<std::endl;
            }
        } 

        // osg::Timer_t end_t = osg::Timer::instance()->tick();
        // osg::notify(osg::NOTICE)<<"Took "<<osg::Timer::instance()->delta_m(start_t,end_t)<<"ms to test "<<numTests<<" out of "<<_nearPlaneCandidateMap.size()<<std::endl;
    }

    if (_computeNearFar && _computed_zfar>=_computed_znear)
    {

        //osg::notify(osg::INFO)<<"clamping "<< "znear="<<_computed_znear << " zfar="<<_computed_zfar<<std::endl;


        // adjust the projection matrix so that it encompases the local coords.
        // so it doesn't cull them out.
        osg::Matrix& projection = *_projectionStack.back();
        
        value_type tmp_znear = _computed_znear;
        value_type tmp_zfar = _computed_zfar;
        
        clampProjectionMatrix(projection, tmp_znear, tmp_zfar);
    }
    else
    {
        //osg::notify(osg::INFO)<<"Not clamping "<< "znear="<<_computed_znear << " zfar="<<_computed_zfar<<std::endl;
    }

    CullStack::popProjectionMatrix();
}

template<class matrix_type, class value_type>
bool _clampProjectionMatrix(matrix_type& projection, double& znear, double& zfar, value_type nearFarRatio)
{
    if (zfar>=znear)
    {

        double epsilon = 1e-6;
        if (fabs(projection(0,3))<epsilon  && fabs(projection(1,3))<epsilon  && fabs(projection(2,3))<epsilon )
        {
            // osg::notify(osg::INFO) << "Orthographic matrix before clamping"<<projection<<std::endl;

            value_type delta_span = (zfar-znear)*0.02;
            if (delta_span<1.0) delta_span = 1.0;
            value_type desired_znear = znear - delta_span;
            value_type desired_zfar = zfar + delta_span;

            // assign the clamped values back to the computed values.
            znear = desired_znear;
            zfar = desired_zfar;

            projection(2,2)=-2.0f/(desired_zfar-desired_znear);
            projection(3,2)=-(desired_zfar+desired_znear)/(desired_zfar-desired_znear);
            
            // osg::notify(osg::INFO) << "Orthographic matrix after clamping "<<projection<<std::endl;

            return true;

        }
        else
        {

            // osg::notify(osg::INFO) << "Persepective matrix before clamping"<<projection<<std::endl;

            //std::cout << "_computed_znear"<<_computed_znear<<std::endl;
            //std::cout << "_computed_zfar"<<_computed_zfar<<std::endl;

            value_type zfarPushRatio = 1.02;
            value_type znearPullRatio = 0.98;
            
            //znearPullRatio = 0.99; 
            
            value_type desired_znear = znear * znearPullRatio;
            value_type desired_zfar = zfar * zfarPushRatio;

            // near plane clamping.
            double min_near_plane = zfar*nearFarRatio;
            if (desired_znear<min_near_plane) desired_znear=min_near_plane;

            // assign the clamped values back to the computed values.
            znear = desired_znear;
            zfar = desired_zfar;

            value_type trans_near_plane = (-desired_znear*projection(2,2)+projection(3,2))/(-desired_znear*projection(2,3)+projection(3,3));
            value_type trans_far_plane = (-desired_zfar*projection(2,2)+projection(3,2))/(-desired_zfar*projection(2,3)+projection(3,3));

            value_type ratio = fabs(2.0/(trans_near_plane-trans_far_plane));
            value_type center = -(trans_near_plane+trans_far_plane)/2.0;
            
            projection.postMult(osg::Matrix(1.0f,0.0f,0.0f,0.0f,
                                            0.0f,1.0f,0.0f,0.0f,
                                            0.0f,0.0f,ratio,0.0f,
                                            0.0f,0.0f,center*ratio,1.0f));
                                            
            // osg::notify(osg::INFO) << "Persepective matrix after clamping"<<projection<<std::endl;

            return true;
        }
    }
    return false;
}


bool CullVisitor::clampProjectionMatrixImplementation(osg::Matrixf& projection, double& znear, double& zfar) const
{
    return _clampProjectionMatrix( projection, znear, zfar, _nearFarRatio );
}

bool CullVisitor::clampProjectionMatrixImplementation(osg::Matrixd& projection, double& znear, double& zfar) const
{
    return _clampProjectionMatrix( projection, znear, zfar, _nearFarRatio );
}

struct ComputeNearestPointFunctor
{

    ComputeNearestPointFunctor():
        _planes(0) {}

    void set(CullVisitor::value_type znear, const osg::Matrix& matrix, const osg::Polytope::PlaneList* planes)
    {
        _znear = znear;
        _matrix = matrix;
        _planes = planes;
    }

    typedef std::pair<float, osg::Vec3>  DistancePoint;
    typedef std::vector<DistancePoint>  Polygon;

    CullVisitor::value_type         _znear;
    osg::Matrix                     _matrix;
    const osg::Polytope::PlaneList* _planes;
    Polygon                         _polygonOriginal;
    Polygon                         _polygonNew;
    
    Polygon                         _pointCache;

    inline void operator() ( const osg::Vec3 &v1, const osg::Vec3 &v2, const osg::Vec3 &v3, bool)
    {
        CullVisitor::value_type n1 = distance(v1,_matrix);
        CullVisitor::value_type n2 = distance(v2,_matrix);
        CullVisitor::value_type n3 = distance(v3,_matrix);

        // check if triangle is total behind znear, if so disguard
        if (n1 >= _znear &&
            n2 >= _znear &&
            n3 >= _znear)
        {
            //osg::notify(osg::NOTICE)<<"Triangle totally beyond znear"<<std::endl;
            return;
        }
      
        
        if (n1 < 0.0 &&
            n2 < 0.0 &&
            n3 < 0.0)
        {
            // osg::notify(osg::NOTICE)<<"Triangle totally behind eye point"<<std::endl;
            return;
        }

        // check which planes the points
        osg::Polytope::ClippingMask selector_mask = 0x1;
        osg::Polytope::ClippingMask active_mask = 0x0;

        osg::Polytope::PlaneList::const_iterator pitr;
        for(pitr = _planes->begin();
            pitr != _planes->end();
            ++pitr)
        {
            const osg::Plane& plane = *pitr;
            float d1 = plane.distance(v1);
            float d2 = plane.distance(v2);
            float d3 = plane.distance(v3);
            
            unsigned int numOutside = ((d1<0.0)?1:0) + ((d2<0.0)?1:0) + ((d3<0.0)?1:0);
            if (numOutside==3)
            {
                //osg::notify(osg::NOTICE)<<"Triangle totally outside frustum "<<d1<<"\t"<<d2<<"\t"<<d3<<std::endl;
                return;
            }
            unsigned int numInside = ((d1>=0.0)?1:0) + ((d2>=0.0)?1:0) + ((d3>=0.0)?1:0);
            if (numInside<3)
            {
                active_mask = active_mask | selector_mask;
            }
            
            //osg::notify(osg::NOTICE)<<"Triangle ok w.r.t plane "<<d1<<"\t"<<d2<<"\t"<<d3<<std::endl;

            selector_mask <<= 1; 
        }        
    
        if (active_mask==0)
        {
            _znear = osg::minimum(_znear,n1);
            _znear = osg::minimum(_znear,n2);
            _znear = osg::minimum(_znear,n3);
            // osg::notify(osg::NOTICE)<<"Triangle all inside frustum "<<n1<<"\t"<<n2<<"\t"<<n3<<" number of plane="<<_planes->size()<<std::endl;
            return;
        }
        
        //return;
    
        // numPartiallyInside>0) so we have a triangle cutting an frustum wall,
        // this means that use brute force methods for deviding up triangle. 
        
        //osg::notify(osg::NOTICE)<<"Using brute force method of triangle cutting frustum walls"<<std::endl;
        _polygonOriginal.clear();
        _polygonOriginal.push_back(DistancePoint(0,v1));
        _polygonOriginal.push_back(DistancePoint(0,v2));
        _polygonOriginal.push_back(DistancePoint(0,v3));
        
        selector_mask = 0x1;
        

        for(pitr = _planes->begin();
            pitr != _planes->end() && !_polygonOriginal.empty();
            ++pitr)
        {
            if (active_mask & selector_mask)
            {    
                // polygon bisects plane so need to divide it up.
                const osg::Plane& plane = *pitr;
                _polygonNew.clear();

                // assign the distance from the current plane.
                for(Polygon::iterator polyItr = _polygonOriginal.begin();
                    polyItr != _polygonOriginal.end();
                    ++polyItr)
                {
                    polyItr->first = plane.distance(polyItr->second);
                }
                
                // create the new polygon by clamping against the 
                unsigned int psize = _polygonOriginal.size();

                for(unsigned int ci = 0; ci < psize; ++ci)
                {
                    unsigned int ni = (ci+1)%psize;
                    bool computeIntersection = false;
                    if (_polygonOriginal[ci].first>=0.0f)
                    {
                        _polygonNew.push_back(_polygonOriginal[ci]);
                        
                        if (_polygonOriginal[ni].first<0.0f) computeIntersection = true;
                    }
                    else if (_polygonOriginal[ni].first>0.0f) computeIntersection = true;


                    if (computeIntersection)
                    {
                        // segment intersects with the plane, compute new position.
                        float r = _polygonOriginal[ci].first/(_polygonOriginal[ci].first-_polygonOriginal[ni].first);
                        _polygonNew.push_back(DistancePoint(0.0f,_polygonOriginal[ci].second*(1.0f-r) + _polygonOriginal[ni].second*r));
                    }
                }
                _polygonOriginal.swap(_polygonNew);
            }
            selector_mask <<= 1; 
        }

        // now take the nearst points to the eye point.
        for(Polygon::iterator polyItr = _polygonOriginal.begin();
            polyItr != _polygonOriginal.end();
            ++polyItr)
        {
            CullVisitor::value_type dist = distance(polyItr->second,_matrix);
            if (dist < _znear) 
            {
                _znear = dist;
                //osg::notify(osg::NOTICE)<<"Near plane updated "<<_znear<<std::endl;
            }
        }
    }
};

CullVisitor::value_type CullVisitor::computeNearestPointInFrustum(const osg::Matrix& matrix, const osg::Polytope::PlaneList& planes,const osg::Drawable& drawable)
{
    // osg::notify(osg::WARN)<<"CullVisitor::computeNearestPointInFrustum("<<getTraversalNumber()<<"\t"<<planes.size()<<std::endl;

    osg::TriangleFunctor<ComputeNearestPointFunctor> cnpf;
    cnpf.set(_computed_znear, matrix, &planes);
    
    drawable.accept(cnpf);

    return cnpf._znear;
}

bool CullVisitor::updateCalculatedNearFar(const osg::Matrix& matrix,const osg::BoundingBox& bb)
{
    // efficient computation of near and far, only taking into account the nearest and furthest
    // corners of the bounding box.
    value_type d_near = distance(bb.corner(_bbCornerNear),matrix);
    value_type d_far = distance(bb.corner(_bbCornerFar),matrix);

    if (d_near>d_far)
    {
        std::swap(d_near,d_far);
        if ( !EQUAL_F(d_near, d_far) ) 
        {
            osg::notify(osg::WARN)<<"Warning: CullVisitor::updateCalculatedNearFar(.) near>far in range calculation,"<< std::endl;
            osg::notify(osg::WARN)<<"         correcting by swapping values d_near="<<d_near<<" dfar="<<d_far<< std::endl;
        }
    }

    if (d_far<0.0)
    {
        // whole object behind the eye point so disguard
        return false;
    }

    if (d_near<_computed_znear) _computed_znear = d_near;
    if (d_far>_computed_zfar) _computed_zfar = d_far;

    return true;
}

bool CullVisitor::updateCalculatedNearFar(const osg::Matrix& matrix,const osg::Drawable& drawable, bool isBillboard)
{
    const osg::BoundingBox& bb = drawable.getBound();

    value_type d_near, d_far;

    if (isBillboard)
    {
    
#ifdef TIME_BILLBOARD_NEAR_FAR_CALCULATION    
        static unsigned int lastFrameNumber = getTraversalNumber();
        static unsigned int numBillboards = 0;
        static double elapsed_time = 0.0;
        if (lastFrameNumber != getTraversalNumber())
        {
            osg::notify(osg::NOTICE)<<"Took "<<elapsed_time<<"ms to test "<<numBillboards<<" billboards"<<std::endl;
            numBillboards = 0;
            elapsed_time = 0.0;
            lastFrameNumber = getTraversalNumber();
        }
        osg::Timer_t start_t = osg::Timer::instance()->tick();
#endif
        
        osg::Vec3 lookVector(-matrix(0,2),-matrix(1,2),-matrix(2,2));

        unsigned int bbCornerFar = (lookVector.x()>=0?1:0) +
                       (lookVector.y()>=0?2:0) +
                       (lookVector.z()>=0?4:0);

        unsigned int bbCornerNear = (~bbCornerFar)&7;

        d_near = distance(bb.corner(bbCornerNear),matrix);
        d_far = distance(bb.corner(bbCornerFar),matrix);

        osg::notify(osg::NOTICE).precision(15);

        if (false)
        {

            osg::notify(osg::NOTICE)<<"TESTING Billboard near/far computation"<<std::endl;

             // osg::notify(osg::WARN)<<"Checking corners of billboard "<<std::endl;
            // deprecated brute force way, use all corners of the bounding box.
            value_type nd_near, nd_far;
            nd_near = nd_far = distance(bb.corner(0),matrix);
            for(unsigned int i=0;i<8;++i)
            {
                value_type d = distance(bb.corner(i),matrix);
                if (d<nd_near) nd_near = d;
                if (d>nd_far) nd_far = d;
                osg::notify(osg::NOTICE)<<"\ti="<<i<<"\td="<<d<<std::endl;
            }

            if (nd_near==d_near && nd_far==d_far)
            {
                osg::notify(osg::NOTICE)<<"\tBillboard near/far computation correct "<<std::endl;
            }
            else
            {
                osg::notify(osg::NOTICE)<<"\tBillboard near/far computation ERROR\n\t\t"<<d_near<<"\t"<<nd_near
                                        <<"\n\t\t"<<d_far<<"\t"<<nd_far<<std::endl;
            }

        }

#ifdef TIME_BILLBOARD_NEAR_FAR_CALCULATION    
        osg::Timer_t end_t = osg::Timer::instance()->tick();
        
        elapsed_time += osg::Timer::instance()->delta_m(start_t,end_t);
        ++numBillboards;
#endif
    }
    else
    {
        // efficient computation of near and far, only taking into account the nearest and furthest
        // corners of the bounding box.
        d_near = distance(bb.corner(_bbCornerNear),matrix);
        d_far = distance(bb.corner(_bbCornerFar),matrix);
    }
    
    if (d_near>d_far)
    {
        std::swap(d_near,d_far);
        if ( !EQUAL_F(d_near, d_far) ) 
        {
            osg::notify(osg::WARN)<<"Warning: CullVisitor::updateCalculatedNearFar(.) near>far in range calculation,"<< std::endl;
            osg::notify(osg::WARN)<<"         correcting by swapping values d_near="<<d_near<<" dfar="<<d_far<< std::endl;
        }
    }

    if (d_far<0.0)
    {
        // whole object behind the eye point so disguard
        return false;
    }

    if (d_near<_computed_znear) 
    {
        if (_computeNearFar==COMPUTE_NEAR_FAR_USING_PRIMITIVES)
        {
            osg::Polytope& frustum = getCurrentCullingSet().getFrustum();
            if (frustum.getCurrentMask() && frustum.getResultMask())
            {
                if (isBillboard)
                {
                    // osg::notify(osg::WARN)<<"Adding billboard into deffered list"<<std::endl;
                
                    osg::Polytope transformed_frustum;
                    transformed_frustum.setAndTransformProvidingInverse(getProjectionCullingStack().back().getFrustum(),matrix);
                
                    // insert drawable into the deferred list of drawables which will be handled at the popProjectionMatrix().
                    _nearPlaneCandidateMap.insert(
                        DistanceMatrixDrawableMap::value_type(d_near,MatrixPlanesDrawables(matrix,&drawable,transformed_frustum)) );
                } 
                else
                {
                    // insert drawable into the deferred list of drawables which will be handled at the popProjectionMatrix().
                    _nearPlaneCandidateMap.insert(
                        DistanceMatrixDrawableMap::value_type(d_near,MatrixPlanesDrawables(matrix,&drawable,frustum)) );
                }
            
      
                                    
                // use the far point if its nearer than current znear as this is a conservative estimate of the znear
                // while the final computation for this drawable is deferred.
                if (d_far<_computed_znear)
                {
                    if (d_far<0.0) osg::notify(osg::WARN)<<"       1)  sett near with dnear="<<d_near<<"  dfar="<<d_far<< std::endl;
                    else _computed_znear = d_far;
                }
                
            }
            else
            {
                
                if (d_near<0.0) osg::notify(osg::WARN)<<"        2) sett near with d_near="<<d_near<< std::endl;
                else _computed_znear = d_near;
            }
            
        }
        else
        {
            //if (d_near<0.0) osg::notify(osg::WARN)<<"         3) set near with d_near="<<d_near<< std::endl;
            _computed_znear = d_near;
        }
    }    

    if (d_far>_computed_zfar) _computed_zfar = d_far;


/*
    // deprecated brute force way, use all corners of the bounding box.
    updateCalculatedNearFar(bb.corner(0));
    updateCalculatedNearFar(bb.corner(1));
    updateCalculatedNearFar(bb.corner(2));
    updateCalculatedNearFar(bb.corner(3));
    updateCalculatedNearFar(bb.corner(4));
    updateCalculatedNearFar(bb.corner(5));
    updateCalculatedNearFar(bb.corner(6));
    updateCalculatedNearFar(bb.corner(7));
*/

    return true;

}
void CullVisitor::updateCalculatedNearFar(const osg::Vec3& pos)
{
    float d;
    if (!_modelviewStack.empty())
    {
        const osg::Matrix& matrix = *(_modelviewStack.back());
        d = distance(pos,matrix);
    }
    else
    {
        d = -pos.z();
    }

    if (d<_computed_znear) 
    {
       _computed_znear = d;
       if (d<0.0) osg::notify(osg::WARN)<<"Alerting billboard ="<<d<< std::endl;
    }
    if (d>_computed_zfar) _computed_zfar = d;
}   

void CullVisitor::apply(Node& node)
{
    if (isCulled(node)) return;

    // push the culling mode.
    pushCurrentMask();
    
    // push the node's state.
    StateSet* node_state = node.getStateSet();
    if (node_state) pushStateSet(node_state);

    handle_cull_callbacks_and_traverse(node);

    // pop the node's state off the geostate stack.    
    if (node_state) popStateSet();
    
    // pop the culling mode.
    popCurrentMask();
}


void CullVisitor::apply(Geode& node)
{
    if (isCulled(node)) return;

    // push the node's state.
    StateSet* node_state = node.getStateSet();
    if (node_state) pushStateSet(node_state);

    // traverse any call callbacks and traverse any children.
    handle_cull_callbacks_and_traverse(node);

    RefMatrix& matrix = getModelViewMatrix();
    for(unsigned int i=0;i<node.getNumDrawables();++i)
    {
        Drawable* drawable = node.getDrawable(i);
        const BoundingBox &bb =drawable->getBound();

        if( drawable->getCullCallback() )
        {
            if( drawable->getCullCallback()->cull( this, drawable, _state.valid()?_state.get():NULL ) == true )
            continue;
        }
        
        //else
        {
            if (node.isCullingActive() && isCulled(bb)) continue;
        }


        if (_computeNearFar && bb.valid()) 
        {
            if (!updateCalculatedNearFar(matrix,*drawable,false)) continue;
        }

        // push the geoset's state on the geostate stack.    
        StateSet* stateset = drawable->getStateSet();
        if (stateset) pushStateSet(stateset);

        if (bb.valid()) addDrawableAndDepth(drawable,&matrix,distance(bb.center(),matrix));
	else addDrawableAndDepth(drawable,&matrix,0.0f);

        if (stateset) popStateSet();

    }

    // pop the node's state off the geostate stack.    
    if (node_state) popStateSet();

}


void CullVisitor::apply(Billboard& node)
{
    if (isCulled(node)) return;

    // push the node's state.
    StateSet* node_state = node.getStateSet();
    if (node_state) pushStateSet(node_state);

    // traverse any call callbacks and traverse any children.
    handle_cull_callbacks_and_traverse(node);

    const Vec3& eye_local = getEyeLocal();
    const RefMatrix& modelview = getModelViewMatrix();

    for(unsigned int i=0;i<node.getNumDrawables();++i)
    {
        const Vec3& pos = node.getPosition(i);

        Drawable* drawable = node.getDrawable(i);
        // need to modify isCulled to handle the billboard offset.
        // if (isCulled(drawable->getBound())) continue;

        RefMatrix* billboard_matrix = createOrReuseMatrix(modelview);

        node.computeMatrix(*billboard_matrix,eye_local,pos);


        if (_computeNearFar && drawable->getBound().valid()) updateCalculatedNearFar(*billboard_matrix,*drawable,true);
        float d = distance(pos,modelview);
/*
        if (_computeNearFar)
        {
            if (d<_computed_znear)
            {
                if (d<0.0) osg::notify(osg::WARN)<<"Alerting billboard handling ="<<d<< std::endl;
                _computed_znear = d;
            }
            if (d>_computed_zfar) _computed_zfar = d;
        }
*/
        StateSet* stateset = drawable->getStateSet();
        if (stateset) pushStateSet(stateset);
        
        addDrawableAndDepth(drawable,billboard_matrix,d);

        if (stateset) popStateSet();

    }

    // pop the node's state off the geostate stack.    
    if (node_state) popStateSet();

}


void CullVisitor::apply(LightSource& node)
{
    // push the node's state.
    StateSet* node_state = node.getStateSet();
    if (node_state) pushStateSet(node_state);

    StateAttribute* light = node.getLight();
    if (light)
    {
        if (node.getReferenceFrame()==osg::LightSource::RELATIVE_RF)
        {
            RefMatrix& matrix = getModelViewMatrix();
            addPositionedAttribute(&matrix,light);
        }
        else
        {
            // relative to absolute.
            addPositionedAttribute(0,light);
        }
    }

    handle_cull_callbacks_and_traverse(node);

    // pop the node's state off the geostate stack.    
    if (node_state) popStateSet();
}

void CullVisitor::apply(ClipNode& node)
{
    // push the node's state.
    StateSet* node_state = node.getStateSet();
    if (node_state) pushStateSet(node_state);

    RefMatrix& matrix = getModelViewMatrix();

    const ClipNode::ClipPlaneList& planes = node.getClipPlaneList();
    for(ClipNode::ClipPlaneList::const_iterator itr=planes.begin();
        itr!=planes.end();
        ++itr)
    {
        addPositionedAttribute(&matrix,itr->get());
    }

    handle_cull_callbacks_and_traverse(node);

    // pop the node's state off the geostate stack.    
    if (node_state) popStateSet();
}

void CullVisitor::apply(TexGenNode& node)
{
    // push the node's state.
    StateSet* node_state = node.getStateSet();
    if (node_state) pushStateSet(node_state);

    RefMatrix& matrix = getModelViewMatrix();

    addPositionedTextureAttribute(node.getTextureUnit(), &matrix,node.getTexGen());

    handle_cull_callbacks_and_traverse(node);

    // pop the node's state off the geostate stack.    
    if (node_state) popStateSet();
}

void CullVisitor::apply(Group& node)
{
    if (isCulled(node)) return;

    // push the culling mode.
    pushCurrentMask();

    // push the node's state.
    StateSet* node_state = node.getStateSet();
    if (node_state) pushStateSet(node_state);

    handle_cull_callbacks_and_traverse(node);

    // pop the node's state off the render graph stack.    
    if (node_state) popStateSet();

    // pop the culling mode.
    popCurrentMask();
}

void CullVisitor::apply(Transform& node)
{
    if (isCulled(node)) return;

    // push the culling mode.
    pushCurrentMask();

    // push the node's state.
    StateSet* node_state = node.getStateSet();
    if (node_state) pushStateSet(node_state);

    ref_ptr<RefMatrix> matrix = createOrReuseMatrix(getModelViewMatrix());
    node.computeLocalToWorldMatrix(*matrix,this);
    pushModelViewMatrix(matrix.get());
    
    handle_cull_callbacks_and_traverse(node);

    popModelViewMatrix();

    // pop the node's state off the render graph stack.    
    if (node_state) popStateSet();

    // pop the culling mode.
    popCurrentMask();
}

void CullVisitor::apply(Projection& node)
{

    // push the culling mode.
    pushCurrentMask();

    // push the node's state.
    StateSet* node_state = node.getStateSet();
    if (node_state) pushStateSet(node_state);


    // record previous near and far values.
    float previous_znear = _computed_znear;
    float previous_zfar = _computed_zfar;
    
    // take a copy of the current near plane candidates
    DistanceMatrixDrawableMap  previousNearPlaneCandidateMap;
    previousNearPlaneCandidateMap.swap(_nearPlaneCandidateMap);

    _computed_znear = FLT_MAX;
    _computed_zfar = -FLT_MAX;


    ref_ptr<osg::RefMatrix> matrix = createOrReuseMatrix(node.getMatrix());
    pushProjectionMatrix(matrix.get());
    
    //osg::notify(osg::INFO)<<"Push projection "<<*matrix<<std::endl;
    
    // note do culling check after the frustum has been updated to ensure
    // that the node is not culled prematurely.
    if (!isCulled(node))
    {
        handle_cull_callbacks_and_traverse(node);
    }

    popProjectionMatrix();

    //osg::notify(osg::INFO)<<"Pop projection "<<*matrix<<std::endl;

    _computed_znear = previous_znear;
    _computed_zfar = previous_zfar;

    // swap back the near plane candidates
    previousNearPlaneCandidateMap.swap(_nearPlaneCandidateMap);

    // pop the node's state off the render graph stack.    
    if (node_state) popStateSet();

    // pop the culling mode.
    popCurrentMask();
}

void CullVisitor::apply(Switch& node)
{
    apply((Group&)node);
}


void CullVisitor::apply(LOD& node)
{
    if (isCulled(node)) return;

    // push the culling mode.
    pushCurrentMask();

    // push the node's state.
    StateSet* node_state = node.getStateSet();
    if (node_state) pushStateSet(node_state);

    handle_cull_callbacks_and_traverse(node);

    // pop the node's state off the render graph stack.    
    if (node_state) popStateSet();

    // pop the culling mode.
    popCurrentMask();
}

void CullVisitor::apply(osg::ClearNode& node)
{
    // simply override the current earth sky.
    setClearNode(&node);

    // push the node's state.
    StateSet* node_state = node.getStateSet();
    if (node_state) pushStateSet(node_state);

    handle_cull_callbacks_and_traverse(node);

    // pop the node's state off the render graph stack.    
    if (node_state) popStateSet();

}

void CullVisitor::apply(osg::OccluderNode& node)
{
    // need to check if occlusion node is in the occluder
    // list, if so disable the appropriate ShadowOccluderVolume
    disableAndPushOccludersCurrentMask(_nodePath);
    

    if (isCulled(node))
    {
        popOccludersCurrentMask(_nodePath);
        return;
    }

    // push the culling mode.
    pushCurrentMask();

    // push the node's state.
    StateSet* node_state = node.getStateSet();
    if (node_state) pushStateSet(node_state);



    handle_cull_callbacks_and_traverse(node);

    // pop the node's state off the render graph stack.    
    if (node_state) popStateSet();

    // pop the culling mode.
    popCurrentMask();

    // pop the current mask for the disabled occluder
    popOccludersCurrentMask(_nodePath);
}



void CullVisitor::apply(Impostor& node)
{

    if (isCulled(node)) return;

    osg::Vec3 eyeLocal = getEyeLocal();

    // push the culling mode.
    pushCurrentMask();

    // push the node's state.
    StateSet* node_state = node.getStateSet();
    if (node_state) pushStateSet(node_state);

    const BoundingSphere& bs = node.getBound();
    
    unsigned int contextID = 0;
    if (_state.valid()) contextID = _state->getContextID();

    float distance2 = (eyeLocal-bs.center()).length2();
    if (!_impostorActive ||
        distance2*_LODScale*_LODScale<osg::square(node.getImpostorThreshold()) ||
        distance2<bs.radius2()*2.0f)
    {
        // outwith the impostor distance threshold therefore simple
        // traverse the appropriate child of the LOD.
        handle_cull_callbacks_and_traverse(node);
    }
    else if (_viewportStack.empty())
    {
        // need to use impostor but no valid viewport is defined to simply
        // default to using the LOD child as above.
        handle_cull_callbacks_and_traverse(node);
    }
    else
    {    

        // within the impostor distance threshold therefore attempt
        // to use impostor instead.
        
        RefMatrix& matrix = getModelViewMatrix();

        // search for the best fit ImpostorSprite;
        ImpostorSprite* impostorSprite = node.findBestImpostorSprite(contextID,eyeLocal);
        
        if (impostorSprite)
        {
            // impostor found, now check to see if it is good enough to use
            float error = impostorSprite->calcPixelError(getMVPW());

            if (error>_impostorPixelErrorThreshold)
            {
                // chosen impostor sprite pixel error is too great to use
                // from this eye point, therefore invalidate it.
                impostorSprite=NULL;
            }
        }
        

// need to think about sprite reuse and support for multiple context's.

        if (impostorSprite==NULL)
        {
            // no appropriate sprite has been found therefore need to create
            // one for use.
            
            // create the impostor sprite.
            impostorSprite = createImpostorSprite(node);

            //if (impostorSprite) impostorSprite->_color.set(0.0f,0.0f,1.0f,1.0f);

        }
        //else impostorSprite->_color.set(1.0f,1.0f,1.0f,1.0f);
        
        if (impostorSprite)
        {
            
            // update frame number to show that impostor is in action.
            impostorSprite->setLastFrameUsed(getTraversalNumber());

            if (_computeNearFar) updateCalculatedNearFar(matrix,*impostorSprite, false);

            StateSet* stateset = impostorSprite->getStateSet();
            
            if (stateset) pushStateSet(stateset);
            
            addDrawableAndDepth(impostorSprite,&matrix,distance(node.getCenter(),matrix));

            if (stateset) popStateSet();
            
            
        }
        else
        {
           // no impostor has been selected or created so default to 
           // traversing the usual LOD selected child.
            handle_cull_callbacks_and_traverse(node);
        }
                
    }

    // pop the node's state off the render graph stack.    
    if (node_state) popStateSet();

    // pop the culling mode.
    popCurrentMask();
}

ImpostorSprite* CullVisitor::createImpostorSprite(Impostor& node)
{
   
    unsigned int contextID = 0;
    if (_state.valid()) contextID = _state->getContextID();

    // default to true right now, will dertermine if perspective from the
    // projection matrix...
    bool isPerspectiveProjection = true;

    const Matrix& matrix = getModelViewMatrix();
    const BoundingSphere& bs = node.getBound();
    osg::Vec3 eye_local = getEyeLocal();

    if (!bs.valid())
    {
        osg::notify(osg::WARN) << "bb invalid"<<&node<<std::endl;
        return NULL;
    }


    Vec3 eye_world(0.0,0.0,0.0);
    Vec3 center_world = bs.center()*matrix;

    // no appropriate sprite has been found therefore need to create
    // one for use.

    // create the render to texture stage.
    ref_ptr<RenderToTextureStage> rtts = new RenderToTextureStage;

    // set up lighting.
    // currently ignore lights in the scene graph itself..
    // will do later.
    RenderStage* previous_stage = _currentRenderBin->getStage();

    // set up the background color and clear mask.
    osg::Vec4 clear_color = previous_stage->getClearColor();
    clear_color[3] = 0.0f; // set the alpha to zero.
    rtts->setClearColor(clear_color);
    rtts->setClearMask(previous_stage->getClearMask());

    // set up to charge the same RenderStageLighting is the parent previous stage.
    rtts->setRenderStageLighting(previous_stage->getRenderStageLighting());


    // record the render bin, to be restored after creation
    // of the render to text
    RenderBin* previousRenderBin = _currentRenderBin;

    // set the current renderbin to be the newly created stage.
    _currentRenderBin = rtts.get();

    // create quad coords (in local coords)

    Vec3 center_local = bs.center();
    Vec3 camera_up_local = getUpLocal();
    Vec3 lv_local = center_local-eye_local;

    float distance_local = lv_local.length();
    lv_local /= distance_local;
   
    Vec3 sv_local = lv_local^camera_up_local;
    sv_local.normalize();
    
    Vec3 up_local = sv_local^lv_local;
    

    
    float width = bs.radius();
    if (isPerspectiveProjection)
    {
        // expand the width to account for projection onto sprite.
        width *= (distance_local/sqrtf(distance_local*distance_local-bs.radius2()));
    }
    
    // scale up and side vectors to sprite width.
    up_local *= width;
    sv_local *= width;
    
    // create the corners of the sprite.
    Vec3 c00(center_local - sv_local - up_local);
    Vec3 c10(center_local + sv_local - up_local);
    Vec3 c01(center_local - sv_local + up_local);
    Vec3 c11(center_local + sv_local + up_local);
    
// adjust camera left,right,up,down to fit (in world coords)

    Vec3 near_local  ( center_local-lv_local*width );
    Vec3 far_local   ( center_local+lv_local*width );
    Vec3 top_local   ( center_local+up_local);
    Vec3 right_local ( center_local+sv_local);
    
    Vec3 near_world = near_local * matrix;
    Vec3 far_world = far_local * matrix;
    Vec3 top_world = top_local * matrix;
    Vec3 right_world = right_local * matrix;
    
    float znear = (near_world-eye_world).length();
    float zfar  = (far_world-eye_world).length();
        
    float top   = (top_world-center_world).length();
    float right = (right_world-center_world).length();

    znear *= 0.9f;
    zfar *= 1.1f;

    // set up projection.
    osg::RefMatrix* projection = new osg::RefMatrix;
    if (isPerspectiveProjection)
    {
        // deal with projection issue move the top and right points
        // onto the near plane.
        float ratio = znear/(center_world-eye_world).length();
        top *= ratio;
        right *= ratio;
        projection->makeFrustum(-right,right,-top,top,znear,zfar);
    }
    else
    {
        projection->makeOrtho(-right,right,-top,top,znear,zfar);
    }

    pushProjectionMatrix(projection);

    Vec3 rotate_from = bs.center()-eye_local;
    Vec3 rotate_to   = getLookVectorLocal();

    osg::RefMatrix* rotate_matrix = new osg::RefMatrix(
        osg::Matrix::translate(-eye_local)*        
        osg::Matrix::rotate(rotate_from,rotate_to)*
        osg::Matrix::translate(eye_local)*
        getModelViewMatrix());

    // pushing the cull view state will update it so it takes
    // into account the new camera orientation.
    pushModelViewMatrix(rotate_matrix);

    StateSet* localPreRenderState = _impostorSpriteManager->createOrReuseStateSet();

    pushStateSet(localPreRenderState);

    {

        // traversing the usual LOD selected child.
        handle_cull_callbacks_and_traverse(node);

    }

    popStateSet();

    // restore the previous model view matrix.
    popModelViewMatrix();

    // restore the previous model view matrix.
    popProjectionMatrix();

    // restore the previous renderbin.
    _currentRenderBin = previousRenderBin;



    if (rtts->getRenderGraphList().size()==0 && rtts->getRenderBinList().size()==0)
    {
        // getting to this point means that all the subgraph has been
        // culled by small feature culling or is beyond LOD ranges.
        return NULL;
    }




    const osg::Viewport& viewport = *getViewport();
    

    // calc texture size for eye, bs.

    // convert the corners of the sprite (in world coords) into their
    // equivilant window coordinates by using the camera's project method.
    const osg::Matrix& MVPW = getMVPW();
    Vec3 c00_win = c00 * MVPW;
    Vec3 c11_win = c11 * MVPW;

// adjust texture size to be nearest power of 2.

    float s  = c11_win.x()-c00_win.x();
    float t  = c11_win.y()-c00_win.y();

    // may need to reverse sign of width or height if a matrix has
    // been applied which flips the orientation of this subgraph.
    if (s<0.0f) s = -s;
    if (t<0.0f) t = -t;

    // bias value used to assist the rounding up or down of
    // the texture dimensions to the nearest power of two.
    // bias near 0.0 will almost always round down.
    // bias near 1.0 will almost always round up. 
    float bias = 0.7f;

    float sp2 = logf((float)s)/logf(2.0f);
    float rounded_sp2 = floorf(sp2+bias);
    int new_s = (int)(powf(2.0f,rounded_sp2));

    float tp2 = logf((float)t)/logf(2.0f);
    float rounded_tp2 = floorf(tp2+bias);
    int new_t = (int)(powf(2.0f,rounded_tp2));

    // if dimension is bigger than window divide it down.    
    while (new_s>viewport.width()) new_s /= 2;

    // if dimension is bigger than window divide it down.    
    while (new_t>viewport.height()) new_t /= 2;


    // offset the impostor viewport from the center of the main window
    // viewport as often the edges of the viewport might be obscured by
    // other windows, which can cause image/reading writing problems.
    int center_x = viewport.x()+viewport.width()/2;
    int center_y = viewport.y()+viewport.height()/2;

    Viewport* new_viewport = new Viewport;
    new_viewport->setViewport(center_x-new_s/2,center_y-new_t/2,new_s,new_t);
    rtts->setViewport(new_viewport);
    
    localPreRenderState->setAttribute(new_viewport);

    // create the impostor sprite.
    ImpostorSprite* impostorSprite = 
        _impostorSpriteManager->createOrReuseImpostorSprite(new_s,new_t,getTraversalNumber()-_numFramesToKeepImpostorSprites);

    if (impostorSprite==NULL)
    {
        osg::notify(osg::WARN)<<"Warning: unable to create required impostor sprite."<<std::endl;
        return NULL;
    }

    // update frame number to show that impostor is in action.
    impostorSprite->setLastFrameUsed(getTraversalNumber());


    // have successfully created an impostor sprite so now need to
    // add it into the impostor.
    node.addImpostorSprite(contextID,impostorSprite);

    if (_depthSortImpostorSprites)
    {
        // the depth sort bin should probably be user definable,
        // will look into this later. RO July 2001.
        StateSet* stateset = impostorSprite->getStateSet();
        stateset->setRenderBinDetails(10,"DepthSortedBin");
    }
    
    Texture2D* texture = impostorSprite->getTexture();

    // update frame number to show that impostor is in action.
    impostorSprite->setLastFrameUsed(getTraversalNumber());

    Vec3* coords = impostorSprite->getCoords();
    Vec2* texcoords = impostorSprite->getTexCoords();
    
    coords[0] = c01;
    texcoords[0].set(0.0f,1.0f);

    coords[1] = c00;
    texcoords[1].set(0.0f,0.0f);

    coords[2] = c10;
    texcoords[2].set(1.0f,0.0f);

    coords[3] = c11;
    texcoords[3].set(1.0f,1.0f);
    
    impostorSprite->dirtyBound();
    
    Vec3* controlcoords = impostorSprite->getControlCoords();
    
    if (isPerspectiveProjection)
    {
        // deal with projection issue by moving the coorners of the quad
        // towards the eye point.
        float ratio = width/(center_local-eye_local).length();
        float one_minus_ratio = 1.0f-ratio;
        Vec3 eye_local_ratio = eye_local*ratio;
        
        controlcoords[0] = coords[0]*one_minus_ratio + eye_local_ratio;
        controlcoords[1] = coords[1]*one_minus_ratio + eye_local_ratio;
        controlcoords[2] = coords[2]*one_minus_ratio + eye_local_ratio;
        controlcoords[3] = coords[3]*one_minus_ratio + eye_local_ratio;
    }
    else
    {
        // project the control points forward towards the eyepoint,
        // but since this an othographics projection this projection is
        // parallel.
        Vec3 dv = lv_local*width;

        controlcoords[0] = coords[0]-dv;
        controlcoords[1] = coords[1]-dv;
        controlcoords[2] = coords[2]-dv;
        controlcoords[3] = coords[3]-dv;
    }

    impostorSprite->setStoredLocalEyePoint(eye_local);


    // and the render to texture stage to the current stages
    // dependancy list.
    _currentRenderBin->getStage()->addToDependencyList(rtts.get());

    // attach texture to the RenderToTextureStage.
    rtts->setTexture(texture);

    // must sort the RenderToTextureStage so that all leaves are
    // accounted correctly in all renderbins i.e depth sorted bins.    
    rtts->sort();

    return impostorSprite;

}