use face normals map as input of compute_vertex_normal

in the named parameters

Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/compute_normal.h

@@ -32,6 +32,8 @@
 #include <CGAL/Polygon_mesh_processing/internal/named_function_params.h>
 #include <CGAL/Polygon_mesh_processing/internal/named_params_helper.h>
 
+#include <boost/type_traits.hpp>
+
 namespace CGAL{
 
 namespace Polygon_mesh_processing{
@@ -187,6 +189,14 @@ compute_vertex_normal(typename boost::graph_traits<PolygonMesh>::vertex_descript
   typedef typename GetGeomTraits<PolygonMesh, NamedParameters>::type Kernel;
   typedef typename Kernel::FT FT;
 
+  typedef typename GetFaceNormalMap<PolygonMesh, NamedParameters>::type FaceNormalMap;
+  FaceNormalMap fnmap
+    = boost::choose_param(get_param(np, face_normal), FaceNormalMap());
+  bool fnmap_valid
+    = !boost::is_same<FaceNormalMap,
+                      typename GetFaceNormalMap<PolygonMesh, NamedParameters>::NoMap
+                     >::value;
+
   typedef typename Kernel::Vector_3 Vector;
   typedef typename boost::graph_traits<PolygonMesh>::halfedge_descriptor halfedge_descriptor;
 
@@ -197,7 +207,8 @@ compute_vertex_normal(typename boost::graph_traits<PolygonMesh>::vertex_descript
     {
     if (!is_border(he, pmesh))
     {
-      Vector n = compute_face_normal(face(he, pmesh), pmesh, np);
+      Vector n = fnmap_valid ? get(fnmap, face(he, pmesh))
+                             : compute_face_normal(face(he, pmesh), pmesh, np);
       normal = normal + n;
     }
     he = opposite(next(he, pmesh), pmesh);
@@ -279,8 +290,8 @@ compute_normals(const PolygonMesh& pmesh
                 , const NamedParameters& np
                 )
 {
-  compute_vertex_normals(pmesh, vnm, np);
   compute_face_normals(pmesh, fnm, np);
+  compute_vertex_normals(pmesh, vnm, np.face_normal_map(fnm));
 }
 
 ///\cond SKIP_IN_MANUAL

Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/named_function_params.h

@@ -38,6 +38,7 @@ namespace CGAL{
 
   //to be documented
   enum smooth_along_features_t      { smooth_along_features };
+  enum face_normal_t                { face_normal };
 
   //internal
   enum weight_calculator_t          { weight_calculator };
@@ -100,6 +101,14 @@ namespace CGAL{
       return Params(w, *this);
     }
 
+    template <typename FaceNormalMap>
+    pmp_bgl_named_params<FaceNormalMap, face_normal_t, self>
+    face_normal_map(const FaceNormalMap& m) const
+    {
+      typedef pmp_bgl_named_params<FaceNormalMap, face_normal_t, self> Params;
+      return Params(m, *this);
+    }
+
     //overload
     template <typename PointMap>
     pmp_bgl_named_params<PointMap, boost::vertex_point_t, self>
@@ -230,6 +239,14 @@ namespace parameters{
     return Params(w);
   }
 
+  template <typename FaceNormalMap>
+  pmp_bgl_named_params<FaceNormalMap, face_normal_t>
+  face_normal_map(const FaceNormalMap& m)
+  {
+    typedef pmp_bgl_named_params<FaceNormalMap, face_normal_t> Params;
+    return Params(p);
+  }
+
   //overload
   template <typename PointMap>
   pmp_bgl_named_params<PointMap, boost::vertex_point_t>

Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/named_params_helper.h

@@ -100,6 +100,32 @@ public:
   > ::type  type;
 };
 
+template<typename PolygonMesh, typename NamedParameters>
+class GetFaceNormalMap
+{
+  struct DummyNormalPmap
+  {
+    typedef typename boost::graph_traits<PolygonMesh>::face_descriptor key_type;
+    typedef typename GetGeomTraits<PolygonMesh, NamedParameters>::type::Vector_3 value_type;
+    typedef value_type& reference;
+    typedef boost::lvalue_property_map_tag category;
+
+    reference operator[](key_type&) const { return CGAL::NULL_VECTOR; }
+    typedef DummyNormalPmap Self;
+    friend const value_type& get(const Self&, const key_type&) { return CGAL::NULL_VECTOR; }
+    friend         reference get(const Self&, key_type&)       { return CGAL::NULL_VECTOR; }
+    friend void put(const Self&, key_type&, const value_type&) {}
+  };
+
+public:
+  typedef DummyNormalPmap NoMap;
+  typedef typename boost::lookup_named_param_def <
+    CGAL::face_normal_t,
+    NamedParameters,
+    DummyNormalPmap//default
+  > ::type  type;
+};
+
 template<typename NamedParameters, typename DefaultSolver>
 class GetSolver
 {