Added ClipNode::set/getReferenceFrame();

include/osg/ClipNode

@@ -34,10 +34,31 @@ class OSG_EXPORT ClipNode : public Group
 
         META_Node(osg, ClipNode);
     
+        enum ReferenceFrame
+        {
+            RELATIVE_RF,
+            ABSOLUTE_RF
+        };
+        
+        /** Set the light sources's ReferenceFrame, either to be relative to its
+          * parent reference frame, or relative to an absolute coordinate
+          * frame. RELATIVE_RF is the default.
+          * Note: setting the ReferenceFrame to be ABSOLUTE_RF will
+          * also set the CullingActive flag on the light source, and hence all
+          * of its parents, to false, thereby disabling culling of it and
+          * all its parents.  This is necessary to prevent inappropriate
+          * culling, but may impact cull times if the absolute light source is
+          * deep in the scene graph.  It is therefore recommended to only use
+          * absolute light source at the top of the scene.
+        */
+        void setReferenceFrame(ReferenceFrame rf);
+        
+        ReferenceFrame getReferenceFrame() const { return _referenceFrame; }
+
+
         /** Creates six clip planes corresponding to the given BoundingBox. */
         void createClipBox(const BoundingBox& bb,unsigned int clipPlaneNumberBase=0);
 
-
         /** Adds the clipplane. Returns true on success, and false if the plane
           * has already been added, or if clipplane is NULL. */
         bool addClipPlane(ClipPlane* clipplane);
@@ -81,8 +102,10 @@ class OSG_EXPORT ClipNode : public Group
 
         virtual ~ClipNode();
 
-        StateAttribute::GLModeValue _value;
-        ClipPlaneList _planes;
+        StateAttribute::GLModeValue     _value;
+        ClipPlaneList                   _planes;
+        
+        ReferenceFrame                  _referenceFrame;
 };
 
 }