Added osg::CollectOccludersVisitor which is a helper class for finding active

occluder in the view frustum, to be used as pre cull traversal.

src/osg/CollectOccludersVisitor.cpp

@@ -0,0 +1,42 @@
+#include <osg/CollectOccludersVisitor>
+
+using namespace osg;
+
+CollectOccludersVisitor::CollectOccludersVisitor()
+{
+}
+
+CollectOccludersVisitor::~CollectOccludersVisitor()
+{
+}
+
+void CollectOccludersVisitor::reset()
+{
+    CullStack::reset();
+}
+
+void CollectOccludersVisitor::apply(osg::Node&)
+{
+}
+
+void CollectOccludersVisitor::apply(osg::Transform& node)
+{
+}
+
+void CollectOccludersVisitor::apply(osg::Projection& node)
+{
+}
+
+void CollectOccludersVisitor::apply(osg::Switch& node)
+{
+}
+
+void CollectOccludersVisitor::apply(osg::LOD& node)
+{
+}
+
+void CollectOccludersVisitor::apply(osg::OccluderNode& node)
+{
+}
+
+

src/osg/Group.cpp

@@ -3,6 +3,7 @@
 #include <osg/Group>
 #include <osg/BoundingBox>
 #include <osg/Transform>
+#include <osg/OccluderNode>
 
 #include <algorithm>
 
@@ -80,6 +81,14 @@ bool Group::addChild( Node *child )
                 );
         }
 
+        if (child->getNumChildrenWithOccluderNodes()>0 ||
+            dynamic_cast<osg::OccluderNode*>(child))
+        {
+            setNumChildrenWithOccluderNodes(
+                getNumChildrenWithOccluderNodes()+1
+                );
+        }
+
         return true;
     }
     else return false;
@@ -114,6 +123,14 @@ bool Group::removeChild( Node *child )
                 );
         }
 
+        if (child->getNumChildrenWithOccluderNodes()>0 ||
+            dynamic_cast<osg::OccluderNode*>(child))
+        {
+            setNumChildrenWithOccluderNodes(
+                getNumChildrenWithOccluderNodes()-1
+                );
+        }
+
         // note ref_ptr<> automatically handles decrementing child's reference count.
         _children.erase(itr);
         dirtyBound();

src/osg/Makefile

@@ -12,6 +12,7 @@ CXXFILES =\
 	ClipPlane.cpp\
 	ColorMask.cpp\
 	ColorMatrix.cpp\
+	CollectOccludersVisitor.cpp\
 	ConvexPlanerPolygon.cpp\
 	ConvexPlanerOccluder.cpp\
 	CopyOp.cpp\

src/osg/Node.cpp

@@ -2,6 +2,7 @@
 #include <osg/Group>
 #include <osg/NodeVisitor>
 #include <osg/Notify>
+#include <osg/OccluderNode>
 
 #include <algorithm>
 
@@ -17,6 +18,7 @@ Node::Node()
     _cullingActive = true;
     _numChildrenWithCullingDisabled = 0;
 
+    _numChildrenWithOccluderNodes = 0;
 }
 
 Node::Node(const Node& node,const CopyOp& copyop):
@@ -30,6 +32,7 @@ Node::Node(const Node& node,const CopyOp& copyop):
         _cullCallback(node._cullCallback),
         _cullingActive(node._cullingActive),
         _numChildrenWithCullingDisabled(0), // assume no children yet.
+        _numChildrenWithOccluderNodes(0),
         _userData(copyop(node._userData.get())),
         _nodeMask(node._nodeMask), 
         _descriptions(node._descriptions),
@@ -227,6 +230,48 @@ void Node::setNumChildrenWithCullingDisabled(const int num)
 }
 
 
+void Node::setNumChildrenWithOccluderNodes(const int num)
+{
+    // if no changes just return.
+    if (_numChildrenWithOccluderNodes==num) return;
+
+    // note, if this node is a OccluderNode then the
+    // parents won't be affected by any changes to
+    // _numChildrenWithOccluderNodes so no need to inform them.
+    if (!dynamic_cast<OccluderNode*>(this) && !_parents.empty())
+    {
+    
+        // need to pass on changes to parents.        
+        int delta = 0;
+        if (_numChildrenWithOccluderNodes>0) --delta;
+        if (num>0) ++delta;
+        if (delta!=0)
+        {
+            // the number of callbacks has changed, need to pass this
+            // on to parents so they know whether app traversal is
+            // reqired on this subgraph.
+            for(ParentList::iterator itr =_parents.begin();
+                itr != _parents.end();
+                ++itr)
+            {    
+                (*itr)->setNumChildrenWithOccluderNodes(
+                    (*itr)->getNumChildrenWithOccluderNodes()+delta
+                    );
+            }
+
+        }
+    }
+    
+    // finally update this objects value.
+    _numChildrenWithOccluderNodes=num;
+    
+}
+
+const bool Node::containsOccluderNodes() const
+{
+    return _numChildrenWithOccluderNodes>0 || dynamic_cast<const OccluderNode*>(this);
+}
+
 const bool Node::computeBound() const
 {
     _bsphere.init();

src/osgUtil/SceneView.cpp

@@ -8,6 +8,7 @@
 #include <osg/TexEnv>
 #include <osg/ColorMatrix>
 #include <osg/LightModel>
+#include <osg/CollectOccludersVisitor>
 
 #include <osg/GLU>
 
@@ -306,6 +307,34 @@ void SceneView::cullStage(osg::Matrix* projection,osg::Matrix* modelview,osgUtil
     if (!_initCalled) init();
 
 
+    // collect any occluder in the view frustum.
+    if (_sceneData->containsOccluderNodes())
+    {
+        std::cout << "Scene graph contains occluder nodes, searching for them"<<std::endl;
+        osg::CollectOccludersVisitor cov;
+        
+        cov.setFrameStamp(_frameStamp.get());
+
+        // use the frame number for the traversal number.
+        if (_frameStamp.valid())
+        {
+             cov.setTraversalNumber(_frameStamp->getFrameNumber());
+        }
+
+        cov.pushViewport(_viewport.get());
+        cov.pushProjectionMatrix(projection);
+        cov.pushModelViewMatrix(modelview);
+
+        // traverse the scene graph to search for occluder in there new positions.
+        _sceneData->accept(cov);
+
+        cov.popModelViewMatrix();
+        cov.popProjectionMatrix();
+        cov.popViewport();
+
+        std::cout << "finished searching for occluder"<<std::endl;
+    }
+    
 
 
     cullVisitor->reset();