Further work on Occlusion Culling. Most of work is complete, just debugging

required now.

src/osg/CullingSet.cpp

@@ -12,3 +12,21 @@ CullingSet::CullingSet()
 CullingSet::~CullingSet()
 {
 }
+
+void CullingSet::disableOccluder(NodePath& nodePath)
+{
+    //std::cout<<"  trying to disable occluder"<<std::endl;
+    for(OccluderList::iterator itr=_occluderList.begin();
+        itr!=_occluderList.end();
+        ++itr)
+    {
+        if (itr->getNodePath()==nodePath)
+        {
+            //std::cout<<"  ++ disabling occluder"<<std::endl;
+            // we have trapped for the case an occlude potentially occluding itself,
+            // to prevent this we disable the results mask so that no subsequnt 
+            // when the next pushCurrentMask calls happens this occluder is switched off.
+            itr->disableResultMasks();
+        }
+    }
+}