From Luc Frauciel, "osgUtil Tessellator : beginTessellation() made virtual to allow configuration of tessellation:

The initialisation of glu low level tessellator is done in  osgUtil::Tessellator::beginTessellation()
This function is not virtual, preventing any customization of the tesselation.
In particular, there in an option in glu tesselator that force the generated primitives to be triangles and that I'd like to use (GLU_TESS_EDGE_FLAG).
"

include/osgUtil/Tessellator

@@ -96,7 +96,7 @@ class OSGUTIL_EXPORT Tessellator : public osg::Referenced
             VecList _vertices;
         };
         
-        void beginTessellation();
+        virtual void beginTessellation();
         
         void beginContour();