From 5d79eb1c9d1c7a2499a4fe4146841a5cd950e807 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Thu, 29 Apr 2004 22:21:06 +0000
Subject: [PATCH] Added support for fine grained computation of the near plane,
 by taking into account individual primitives culled against the view frustum.

Added better support for computing the near far for billboards.
---
 include/osgUtil/CullVisitor |  48 +++-
 src/osgUtil/CullVisitor.cpp | 459 +++++++++++++++++++++++++++++++++---
 src/osgUtil/SceneView.cpp   |   1 +
 3 files changed, 472 insertions(+), 36 deletions(-)

diff --git a/include/osgUtil/CullVisitor b/include/osgUtil/CullVisitor
index c7fc15b03..a8747bb71 100644
--- a/include/osgUtil/CullVisitor
+++ b/include/osgUtil/CullVisitor
@@ -198,8 +198,12 @@ class OSGUTIL_EXPORT CullVisitor : public osg::NodeVisitor, public osg::CullStac
         
         inline value_type getCalculatedFarPlane() const { return _computed_zfar; }
 
-	void updateCalculatedNearFar(const osg::Matrix& matrix,const osg::Drawable& drawable) { updateCalculatedNearFar(matrix,drawable.getBound()); }
-	void updateCalculatedNearFar(const osg::Matrix& matrix,const osg::BoundingBox& bb);
+        value_type computeNearestPointInFrustum(const osg::Matrix& matrix, const osg::Polytope::PlaneList& planes,const osg::Drawable& drawable);
+
+	bool updateCalculatedNearFar(const osg::Matrix& matrix,const osg::BoundingBox& bb);
+
+	bool updateCalculatedNearFar(const osg::Matrix& matrix,const osg::Drawable& drawable, bool isBillboard=false);
+        
     	void updateCalculatedNearFar(const osg::Vec3& pos);
 		
         /** Add a drawable to current render graph.*/
@@ -341,6 +345,46 @@ class OSGUTIL_EXPORT CullVisitor : public osg::NodeVisitor, public osg::CullStac
         osg::ref_ptr<osg::ImpostorSpriteManager>    _impostorSpriteManager;
 
         osg::ref_ptr<osg::State>                    _state;
+
+
+        struct MatrixPlanesDrawables
+        {
+            MatrixPlanesDrawables(const osg::Matrix& matrix, const osg::Drawable* drawable, const osg::Polytope& frustum):
+                _matrix(matrix),
+                _drawable(drawable)
+            {
+                // create a new list of planes from the active walls of the frustum.
+                osg::Polytope::ClippingMask result_mask = frustum.getResultMask();
+                osg::Polytope::ClippingMask selector_mask = 0x1;
+                for(osg::Polytope::PlaneList::const_iterator itr=frustum.getPlaneList().begin();
+                    itr!=frustum.getPlaneList().end();
+                    ++itr)
+                {
+                    if (result_mask&selector_mask) _planes.push_back(*itr);
+                    selector_mask <<= 1; 
+                }
+            }
+            
+            MatrixPlanesDrawables(const MatrixPlanesDrawables& mpd):
+                _matrix(mpd._matrix),
+                _drawable(mpd._drawable),
+                _planes(mpd._planes) {}
+                
+            MatrixPlanesDrawables& operator = (const MatrixPlanesDrawables& mpd)
+            {
+                _matrix = mpd._matrix;
+                _drawable = mpd._drawable;
+                _planes = mpd._planes;
+                return *this;
+            }
+            
+            osg::Matrix                 _matrix;
+            const osg::Drawable*        _drawable;
+            osg::Polytope::PlaneList    _planes;
+        };
+        
+        typedef std::multimap<value_type, MatrixPlanesDrawables>   DistanceMatrixDrawableMap;
+        DistanceMatrixDrawableMap                                  _nearPlaneCandidateMap;
 	
 };
 
diff --git a/src/osgUtil/CullVisitor.cpp b/src/osgUtil/CullVisitor.cpp
index 6e8c9fbef..3c81a1d9c 100644
--- a/src/osgUtil/CullVisitor.cpp
+++ b/src/osgUtil/CullVisitor.cpp
@@ -22,6 +22,8 @@
 #include <osg/TexEnv>
 #include <osg/AlphaFunc>
 #include <osg/LineSegment>
+#include <osg/TriangleFunctor>
+#include <osg/Geometry>
 
 #include <osgUtil/CullVisitor>
 #include <osgUtil/RenderToTextureStage>
@@ -104,6 +106,7 @@ CullVisitor::CullVisitor():
     _currentReuseRenderLeafIndex(0)
 {
     _impostorSpriteManager = new ImpostorSpriteManager;
+    // _nearFarRatio = 0.000005f;     
 }
 
 
@@ -148,6 +151,8 @@ void CullVisitor::reset()
     
     if (_impostorSpriteManager.valid()) _impostorSpriteManager->reset();
     
+
+    _nearPlaneCandidateMap.clear();
 }
 
 float CullVisitor::getDistanceToEyePoint(const Vec3& pos, bool withLODScale) const
@@ -176,9 +181,36 @@ float CullVisitor::getDistanceFromEyePoint(const osg::Vec3& pos, bool withLODSca
 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>0.0f)
     {
 
+        // osg::notify(osg::WARN)<<"   using "<<_computed_znear<<"\t"<<_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();
@@ -225,8 +257,13 @@ bool _clampProjectionMatrix(matrix_type& projection, double znear, double zfar,
             //std::cout << "_computed_znear"<<_computed_znear<<std::endl;
             //std::cout << "_computed_zfar"<<_computed_zfar<<std::endl;
 
-            value_type desired_znear = znear *0.98;
-            value_type desired_zfar = zfar *1.02;
+            value_type zfarPushRatio = 1.02;
+            value_type znearPullRatio = 0.98;
+            
+            znearPullRatio = 0.99999; 
+            
+            value_type desired_znear = znear * znearPullRatio;
+            value_type desired_zfar = zfar * zfarPushRatio;
 
             // near plane clamping.
             double min_near_plane = zfar*nearFarRatio;
@@ -264,10 +301,364 @@ bool CullVisitor::clampProjectionMatrixImplementation(osg::Matrixd& projection,
     return _clampProjectionMatrix( projection, znear, zfar, _nearFarRatio );
 }
 
-void CullVisitor::updateCalculatedNearFar(const osg::Matrix& matrix,const osg::BoundingBox& bb)
+struct ComputeNearestPointFunctor
 {
-#if 0
-    // brute force way, use all corners of the bounding box.
+
+    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_cast<osg::Drawable&>(drawable).dirtyBound();
+
+    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));
@@ -276,31 +667,10 @@ void CullVisitor::updateCalculatedNearFar(const osg::Matrix& matrix,const osg::B
     updateCalculatedNearFar(bb.corner(5));
     updateCalculatedNearFar(bb.corner(6));
     updateCalculatedNearFar(bb.corner(7));
-#else
+*/
 
-    // 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);
+    return true;
 
-    if (d_near<=d_far)
-    {
-        if (d_near<_computed_znear) _computed_znear = d_near;
-        if (d_far>_computed_zfar) _computed_zfar = d_far;
-    }
-    else
-    {
-        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;
-        }
-        // note, need to reverse the d_near/d_far association because they are
-        // the wrong way around...
-        if (d_far<_computed_znear) _computed_znear = d_far;
-        if (d_near>_computed_zfar) _computed_zfar = d_near;
-    }
-#endif
 }
 void CullVisitor::updateCalculatedNearFar(const osg::Vec3& pos)
 {
@@ -315,7 +685,11 @@ void CullVisitor::updateCalculatedNearFar(const osg::Vec3& pos)
         d = -pos.z();
     }
 
-    if (d<_computed_znear) _computed_znear = d;
+    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;
 }   
 
@@ -362,13 +736,17 @@ void CullVisitor::apply(Geode& node)
             if( drawable->getCullCallback()->cull( this, drawable, _state.valid()?_state.get():NULL ) == true )
             continue;
         }
-        else
+        
+        //else
         {
             if (node.isCullingActive() && isCulled(bb)) continue;
         }
 
 
-        if (_computeNearFar && bb.valid()) updateCalculatedNearFar(matrix,*drawable);
+        if (_computeNearFar && bb.valid()) 
+        {
+            if (!updateCalculatedNearFar(matrix,*drawable,false)) continue;
+        }
 
         // push the geoset's state on the geostate stack.    
         StateSet* stateset = drawable->getStateSet();
@@ -414,13 +792,19 @@ void CullVisitor::apply(Billboard& node)
         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) _computed_znear = d;
+            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);
         
@@ -547,9 +931,14 @@ void CullVisitor::apply(Projection& node)
     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());
     
@@ -560,6 +949,8 @@ void CullVisitor::apply(Projection& node)
     _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();
@@ -726,7 +1117,7 @@ void CullVisitor::apply(Impostor& node)
             // update frame number to show that impostor is in action.
             impostorSprite->setLastFrameUsed(getTraversalNumber());
 
-            if (_computeNearFar) updateCalculatedNearFar(matrix,*impostorSprite);
+            if (_computeNearFar) updateCalculatedNearFar(matrix,*impostorSprite, false);
 
             StateSet* stateset = impostorSprite->getStateSet();
             
diff --git a/src/osgUtil/SceneView.cpp b/src/osgUtil/SceneView.cpp
index 392548730..cb516a515 100644
--- a/src/osgUtil/SceneView.cpp
+++ b/src/osgUtil/SceneView.cpp
@@ -37,6 +37,7 @@ SceneView::SceneView(DisplaySettings* ds)
     _clearColor.set(0.2f, 0.2f, 0.4f, 1.0f);
 
     _computeNearFar = CullVisitor::COMPUTE_NEAR_FAR_USING_BOUNDING_VOLUMES;
+    //_computeNearFar = CullVisitor::COMPUTE_NEAR_FAR_USING_PRIMITIVES;
 
     _cullingMode = osg::CullStack::DEFAULT_CULLING;
     _LODScale = 1.0f;