Minor documentation update

git-svn-id: http://www.openmesh.org/svnrepo/OpenMesh/trunk@367 fdac6126-5c0c-442c-9429-916003d36597

src/OpenMesh/Core/Mesh/PolyMeshT.hh

@@ -229,8 +229,10 @@ public:
   void update_normal(VertexHandle _vh)
   { set_normal(_vh, calc_vertex_normal(_vh)); }
 
-  /** Update normal vectors for all vertices. \attention Needs the
-      Attributes::Normal attribute for faces and vertices. */
+  /** \brief Update normal vectors for all vertices. 
+
+      Uses existing face normals to calculate new vertex normals.
+      \attention Needs the Attributes::Normal attribute for faces and vertices. */
   void update_vertex_normals();
 
   /** Calculate normal vector for vertex _vh by averaging normals