Add linear_subdivision

Subdivision_method_3/doc/Subdivision_method_3/PackageDescription.txt

@@ -46,6 +46,7 @@ The page \ref bgl_namedparameters describes their usage.
 - `CGAL::Subdivision_method_3::Sqrt3()`
 - `CGAL::Subdivision_method_3::CatmullClark_subdivision()`
 - `CGAL::Subdivision_method_3::Loop_subdivision()`
+- `CGAL::Subdivision_method_3::linear_subdivision()`
 - `CGAL::Subdivision_method_3::DooSabin_subdivision()`
 - `CGAL::Subdivision_method_3::Sqrt3_subdivision()`
 

Subdivision_method_3/doc/Subdivision_method_3/Subdivision_method_3.txt

@@ -25,7 +25,7 @@ subdivision methods.
 `Polyhedron_3` and `Surface_mesh`, as they are models of the concept
 `MutableFaceGraph`, and it aims to be easy to use and to extend.
 `Subdivision_method_3` is not a class, but a namespace
-which contains four popular subdivision methods and their refinement
+which contains popular subdivision methods and their refinement
 functions. These include Catmull-Clark, Loop, Doo-Sabin and
 \f$ \sqrt{3}\f$ subdivisions. Variations of these methods can be easily
 extended by substituting the geometry computation of the refinement
@@ -512,11 +512,13 @@ The source codes of `CatmullClark_mask_3`, `Loop_mask_3`,
 `DooSabin_mask_3`, and `Sqrt3_mask_3` are
 the best sources of learning these stencil interfaces.
 
-\section Subdivision_method_3The The Four Subdivision Methods
+\section Subdivision_method_3The Subdivision Methods
 
 `Subdivision_method_3` supports Catmull-Clark, Loop,
 Doo-Sabin and \f$ \sqrt{3}\f$ subdivisions by specializing
 their respective refinement hosts.
+In addition, a linear subdivision host is provided which
+enable the user to perform an upsampling of a triangle mesh.
 They are designed to work on any model of a `MutableFaceGraph`
 such as `Polyhedron_3` and `Surface_mesh`. If your application
 uses a polygon mesh with a specialized geometry kernel, you need to
@@ -536,6 +538,11 @@ namespace Subdivision_method_3 {
     PTQ(pmesh, Loop_mask_3<PolygonMesh>(pmesh) , np);
   }
 
+  template <class PolygonMesh, class NamedParameters>
+  void linear_subdivision(PolygonMesh& pmesh, NamedParameters np) {
+    PTQ(pmesh, Linear_mask_3<PolygonMesh>(pmesh), np);
+  }
+
   template <class PolygonMesh, class NamedParameters>
   void DooSabin_subdivision(PolygonMesh& pmesh, NamedParameters np) {
     DQQ(pmesh, DooSabin_mask_3<PolygonMesh>(pmesh), np);
@@ -552,8 +559,8 @@ namespace Subdivision_method_3 {
 
 \section Subdivision_method_3Other Example: Customizing a Subdivision Method
 
-`Subdivision_method_3` supports four practical subdivision methods on a
-`Polyhedron_3` with points with %Cartesian coordinates. More subdivision methods can be supported
+`Subdivision_method_3` supports four practical subdivision methods on a polyhedral mesh
+with points with %Cartesian coordinates. More subdivision methods can be supported
 through the specialization of refinement hosts with custom geometry masks.
 The following example develops a subdivision method
 generating an improved Loop subdivision surface.

Subdivision_method_3/include/CGAL/Subdivision_method_3/subdivision_methods_3.h

@@ -201,10 +201,10 @@ void Loop_subdivision(PolygonMesh& pmesh, const NamedParameters& np = parameters
 
 /*!
  *
- * applies Upsample subdivision several times on the control mesh `pmesh`.
- * The geometry of the refined mesh is computed by the geometry policy mask `Upsample_mask_3`.
- * Which is similar to Loop subdivision but does not change the shape of the mesh (only the connectivity).
- * The new vertices are trivially computed as the average of the incident vertices (midpoint of edge).
+ * applies an  subdivision several times on the control mesh `pmesh`.
+ * The geometry of the refined mesh is computed by the geometry policy mask `Linear_mask_3`,
+ * which is similar to Loop subdivision but does not change the shape of the mesh (only the connectivity).
+ * The new vertices are trivially computed as the average of the incident vertices (e.g., midpoint of an edge).
  * This function overwrites the control mesh `pmesh` with the subdivided mesh.
 
  * @tparam PolygonMesh a model of `MutableFaceGraph`
@@ -233,7 +233,7 @@ void Loop_subdivision(PolygonMesh& pmesh, const NamedParameters& np = parameters
  * \pre `pmesh` must be a triangle mesh.
  **/
 template <class PolygonMesh, class NamedParameters = parameters::Default_named_parameters>
-void Upsample_subdivision(PolygonMesh& pmesh, const NamedParameters& np = parameters::default_values()) {
+void linear_subdivision(PolygonMesh& pmesh, const NamedParameters& np = parameters::default_values()) {
   using parameters::choose_parameter;
   using parameters::get_parameter;
 
@@ -242,11 +242,12 @@ void Upsample_subdivision(PolygonMesh& pmesh, const NamedParameters& np = parame
                          get_property_map(CGAL::vertex_point, pmesh));
 
   unsigned int step = choose_parameter(get_parameter(np, internal_np::number_of_iterations), 1);
-  Upsample_mask_3<PolygonMesh,Vpm> mask(&pmesh, vpm);
+  Linear_mask_3<PolygonMesh,Vpm> mask(&pmesh, vpm);
 
   for(unsigned int i = 0; i < step; i++)
     internal::PTQ_1step(pmesh, vpm, mask);
 }
+
 // -----------------------------------------------------------------------------
 
 #ifndef DOXYGEN_RUNNING

Subdivision_method_3/test/Subdivision_method_3/test_Subdivision_method_3.cpp

@@ -265,6 +265,30 @@ void test_Subdivision_surface_3_SM_NP() {
     assert(CGAL::is_valid_polygon_mesh(P));
   }
 
+  // test linear subdivision on tri mesh
+  {
+    ifstream mesh(TESTMESH_TRI);
+
+    Polyhedron P;
+    mesh >> P;
+
+    Subdivision_method_3::linear_subdivision(P,Subdivision_method_3::parameters::vertex_point_map(get(vertex_point, P))
+                                                                                .number_of_iterations(TEST_DEPTH));
+    assert(CGAL::is_valid_polygon_mesh(P));
+  }
+
+  // test linear subdivision on 'opened' tri mesh
+  {
+    ifstream mesh(TESTMESH_TRI_OPEN);
+
+    Polyhedron P;
+    mesh >> P;
+
+    Subdivision_method_3::linear_subdivision(P,Subdivision_method_3::parameters::vertex_point_map(get(vertex_point, P))
+                                                                                .number_of_iterations(TEST_DEPTH));
+    assert(CGAL::is_valid_polygon_mesh(P));
+  }
+
   // test Doo-Sabin subdivision on 'opened' tri mesh
   {
     ifstream mesh(TESTMESH_TRI_OPEN);