Added CullCallbacks to osg::Node, and osgUtil::CullVisitor.

include/osg/Node

@@ -112,6 +112,15 @@ class SG_EXPORT Node : public Object
         inline const int getNumChildrenRequiringAppTraversal() const { return _numChildrenRequiringAppTraversal; }
 
 
+        /** Set cull node callback, called during cull traversal. */
+        void setCullCallback(NodeCallback* nc) { _cullCallback = nc; }
+
+        /** Get app node callback, called during app traversal. */
+        inline NodeCallback* getCullCallback() { return _cullCallback.get(); }
+
+        /** Get const app node callback, called during app traversal. */
+        inline const NodeCallback* getCullCallback() const { return _cullCallback.get(); }
+
         /** Set the view frustum/small feature culling of this node to be active or inactive.
           * The default value to true for _cullingActive. Used a guide
           * to the cull traversal.*/
@@ -220,6 +229,8 @@ class SG_EXPORT Node : public Object
         int _numChildrenRequiringAppTraversal;
         void setNumChildrenRequiringAppTraversal(const int num);
 
+        ref_ptr<NodeCallback> _cullCallback;
+
         bool _cullingActive;
         int _numChildrenWithCullingDisabled;        
         void setNumChildrenWithCullingDisabled(const int num);

include/osg/NodeCallback

@@ -22,7 +22,13 @@ class SG_EXPORT NodeCallback : public Referenced {
         
         
         /** Callback method call by the NodeVisitor when visiting a node.*/
-        virtual void operator()(Node*, NodeVisitor*) {}
+        virtual void operator()(Node* node, NodeVisitor* nv)
+        { 
+            // note, callback is repsonsible for scenegraph traversal so
+            // should always include call the traverse(node,nv) to ensure 
+            // that the rest of cullbacks and the scene graph are traversed.
+            traverse(node,nv);
+        }
         
         /** Call any nested callbacks and then traverse the scene graph. */
         void traverse(Node* node,NodeVisitor* nv);