Beginning of crease angle support for SmoothingVisitor to all it duplicate vertices are creases

thus enabling separate normals for triangles adjacent to the creases.

include/osgUtil/SmoothingVisitor

@@ -34,11 +34,20 @@ class OSGUTIL_EXPORT SmoothingVisitor : public osg::NodeVisitor
         virtual ~SmoothingVisitor();
         
         /// smooth geoset by creating per vertex normals.
-        static void smooth(osg::Geometry& geoset);
+        static void smooth(osg::Geometry& geoset, double creaseAngle=osg::PI);
 
         /// apply smoothing method to all geode geosets.
         virtual void apply(osg::Geode& geode);
 
+        /// set the maximum angle, in radians, at which angle between adjacent triangles that normals are smoothed
+        /// for edges that greater the shared vertices are duplicated
+        void setCreaseAngle(double angle) { _creaseAngle = angle; }
+        double getCreaseAngle() const { return _creaseAngle; }
+
+    protected:
+
+        double _creaseAngle;
+
 };
 
 }