Add an Euler operation to remove degree 2 vertices

BGL/include/CGAL/boost/graph/Euler_operations.h

@@ -12,10 +12,6 @@
 #ifndef CGAL_EULER_OPERATIONS_H
 #define CGAL_EULER_OPERATIONS_H
 
-#include <stdexcept>
-#include <algorithm>
-#include <vector>
-
 #include <boost/graph/graph_traits.hpp>
 #include <CGAL/boost/graph/properties.h>
 
@@ -27,6 +23,10 @@
 
 #include <boost/container/small_vector.hpp>
 
+#include <algorithm>
+#include <stdexcept>
+#include <vector>
+
 namespace CGAL {
 
 /// \cond SKIP_IN_MANUAL
@@ -1866,10 +1866,72 @@ bool satisfies_link_condition(typename boost::graph_traits<Graph>::edge_descript
 }
 /// \endcond
 #endif
+
+/// removes the target vertex of `h`, merging its incident edges into a single edge.
+/// \pre `degree(target(h, g), g) == 2`.
+/// \pre there is no pre-existing edge between source(h, g) and target(next(h, g), g)
+template <typename Graph>
+typename boost::graph_traits<Graph>::halfedge_descriptor
+remove_degree_2_vertex(const typename boost::graph_traits<Graph>::halfedge_descriptor h,
+                       Graph& g)
+{
+  typedef boost::graph_traits<Graph> Traits;
+  typedef typename Traits::vertex_descriptor   vertex_descriptor;
+  typedef typename Traits::halfedge_descriptor halfedge_descriptor;
+  typedef typename Traits::face_descriptor face_descriptor;
+
+  CGAL_precondition(degree(target(h, g), g) == 2);
+
+  vertex_descriptor v = target(h, g);
+  halfedge_descriptor h1 = h;
+  halfedge_descriptor h2 = opposite(next(h1, g), g);
+
+  if(is_border(h1, g))
+    std::swap(h1, h2);
+
+  vertex_descriptor v1 = source(h1, g);
+  vertex_descriptor v2 = source(h2, g);
+
+  bool exists;
+  halfedge_descriptor huv;
+  std::tie(huv, exists) = halfedge(v1, v2, g);
+  if(exists)
+    return boost::graph_traits<Graph>::null_halfedge();
+
+  if(is_border(h2, g))
+  {
+    CGAL_assertion(!is_border(h1, g));
+
+    halfedge_descriptor oh1 = opposite(h1, g);
+    halfedge_descriptor nnh1 = next(next(h1, g), g);
+    halfedge_descriptor ph2 = prev(h2, g);
+    face_descriptor f1 = face(h1, g);
+
+    set_target(h1, v2, g);
+    set_halfedge(v2, ph2, g);
+    set_next(h1, nnh1, g);
+    set_next(ph2, oh1, g);
+    set_halfedge(f1, h1, g); // in case it was nh1
+
+    remove_edge(edge(h2, g), g);
+    remove_vertex(v, g);
+
+    return h1;
+  }
+  else
+  {
+    CGAL_assertion(!is_border(h1, g) && !is_border(h2, g));
+
+    halfedge_descriptor ph1 = prev(h1, g);
+    halfedge_descriptor ph2 = prev(h2, g);
+    Euler::remove_center_vertex(h, g);
+    return Euler::split_face(ph1, ph2, g);
+  }
+}
+
 /// @}
 
 } // namespace Euler
-
 } // namespace CGAL
 
 #endif /* CGAL_EULER_OPERATIONS_H */

Lab/demo/Lab/Plugins/PMP/Orient_soup_plugin.cpp

@@ -109,28 +109,28 @@ QList<QAction*> CGAL_Lab_orient_soup_plugin::actions() const {
       << actionClean;
 }
 
-void set_vcolors(SMesh* smesh, std::vector<CGAL::IO::Color> colors)
+void set_vcolors(SMesh* smesh, const std::vector<CGAL::IO::Color>& colors)
 {
   typedef SMesh SMesh;
   typedef boost::graph_traits<SMesh>::vertex_descriptor vertex_descriptor;
-  SMesh::Property_map<vertex_descriptor, CGAL::IO::Color> vcolors =
-    smesh->property_map<vertex_descriptor, CGAL::IO::Color >("v:color").value();
+
+  SMesh::Property_map<vertex_descriptor, CGAL::IO::Color> vcolors;
   bool created;
-  boost::tie(vcolors, created) = smesh->add_property_map<SMesh::Vertex_index,CGAL::IO::Color>("v:color",CGAL::IO::Color(0,0,0));
+  std::tie(vcolors, created) = smesh->add_property_map<vertex_descriptor,CGAL::IO::Color>("v:color",CGAL::IO::Color(0,0,0));
   assert(colors.size()==smesh->number_of_vertices());
   int color_id = 0;
   for(vertex_descriptor vd : vertices(*smesh))
       vcolors[vd] = colors[color_id++];
 }
 
-void set_fcolors(SMesh* smesh, std::vector<CGAL::IO::Color> colors)
+void set_fcolors(SMesh* smesh, const std::vector<CGAL::IO::Color>& colors)
 {
   typedef SMesh SMesh;
   typedef boost::graph_traits<SMesh>::face_descriptor face_descriptor;
-  SMesh::Property_map<face_descriptor, CGAL::IO::Color> fcolors =
-    smesh->property_map<face_descriptor, CGAL::IO::Color >("f:color").value();
+
+  SMesh::Property_map<face_descriptor, CGAL::IO::Color> fcolors;
   bool created;
-   boost::tie(fcolors, created) = smesh->add_property_map<SMesh::Face_index,CGAL::IO::Color>("f:color",CGAL::IO::Color(0,0,0));
+  std::tie(fcolors, created) = smesh->add_property_map<face_descriptor,CGAL::IO::Color>("f:color",CGAL::IO::Color(0,0,0));
   assert(colors.size()==smesh->number_of_faces());
   int color_id = 0;
   for(face_descriptor fd : faces(*smesh))

Lab/demo/Lab/Plugins/PMP/Selection_plugin.cpp

@@ -977,13 +977,19 @@ public Q_SLOTS:
     }
     //Add vertex and face to border
     case 9:
+    {
+      QPixmap pm(":/cgal/Lab/resources/euler_deg2.png");
+      ui_widget.docImage_Label->setPixmap(pm);
+      break;
+    }
+    case 10:
     {
       QPixmap pm(":/cgal/Lab/resources/add_facet1.png");
       ui_widget.docImage_Label->setPixmap(pm);
       break;
     }
     //add facet to border
-    case 10:
+    case 11:
     {
       QPixmap pm(":/cgal/Lab/resources/add_facet2.png");
       ui_widget.docImage_Label->setPixmap(pm);

Lab/demo/Lab/Plugins/PMP/Selection_widget.ui

@@ -6,7 +6,7 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>613</width>
+    <width>630</width>
     <height>409</height>
    </rect>
   </property>
@@ -21,7 +21,6 @@
        <widget class="QPushButton" name="Create_selection_item_button">
         <property name="font">
          <font>
-          <weight>75</weight>
           <bold>true</bold>
          </font>
         </property>
@@ -72,7 +71,7 @@
     <item>
      <widget class="QTabWidget" name="selectionOrEuler">
       <property name="currentIndex">
-       <number>0</number>
+       <number>1</number>
       </property>
       <widget class="QWidget" name="tab_3">
        <attribute name="title">
@@ -618,6 +617,11 @@
                  <string>Remove center vertex</string>
                 </property>
                </item>
+               <item>
+                <property name="text">
+                 <string>Remove degree 2 vertex</string>
+                </property>
+               </item>
                <item>
                 <property name="text">
                  <string>Add vertex and face to border (Advanced)</string>
@@ -638,7 +642,7 @@
              <item>
               <widget class="QLabel" name="instructionsLabel">
                <property name="text">
-                <string>Instructions 
+                <string>Instructions
 
 </string>
                </property>

Lab/demo/Lab/Scene_polyhedron_selection_item.cpp

@@ -779,19 +779,26 @@ void Scene_polyhedron_selection_item::set_operation_mode(int mode)
     //set the selection type to vertex
     set_active_handle_type(static_cast<Active_handle::Type>(0));
     break;
-    //Add vertex and face to border
+    //Remove degree 2 vertex
   case 9:
+    Q_EMIT updateInstructions("Select the vertex you want to remove."
+                              "Warning: This will clear the undo stack.");
+    //set the selection type to vertex
+    set_active_handle_type(static_cast<Active_handle::Type>(0));
+    break;
+    //Add vertex and face to border
+  case 10:
     Q_EMIT updateInstructions("Select a border edge. (1/2)");
     //set the selection type to Edge
     set_active_handle_type(static_cast<Active_handle::Type>(2));
     break;
     //Add face to border
-  case 10:
+  case 11:
     Q_EMIT updateInstructions("Select a border edge. (1/2)");
     //set the selection type to Edge
     set_active_handle_type(static_cast<Active_handle::Type>(2));
     break;
-  case 11:
+  case 12:
     Q_EMIT updateInstructions("Select a vertex. (1/2)");
     //set the selection type to Edge
     set_active_handle_type(static_cast<Active_handle::Type>(0));
@@ -1011,7 +1018,24 @@ bool Scene_polyhedron_selection_item::treat_selection(const std::set<fg_vertex_d
       }
       break;
     }
-    case 11:
+      //Remove degree 2 vertex
+    case 9:
+    {
+      if(degree(vh,*polyhedron()) == 2)
+      {
+        CGAL::Euler::remove_degree_2_vertex(halfedge(vh,*polyhedron()), *polyhedron());
+        polyhedron_item()->invalidateOpenGLBuffers();
+      }
+      else
+      {
+        d->tempInstructions("Vertex not selected: The vertex must have degree 2 (and not be incident to a triangle)",
+                  "Select the vertex you want to remove."
+                  "Warning: This will clear the undo stack.");
+      }
+      break;
+    }
+      //Move point
+    case 12:
       CGAL::QGLViewer* viewer = Three::mainViewer();
       const CGAL::qglviewer::Vec offset = viewer->offset();
       if(viewer->manipulatedFrame() != d->manipulated_frame)
@@ -1056,13 +1080,6 @@ bool Scene_polyhedron_selection_item::treat_selection(const std::set<fg_vertex_d
   return false;
 }
 
-//returns true if halfedge's facet's degree >= degree
-/*
-std::size_t facet_degree(fg_halfedge_descriptor h, const Face_graph& polyhedron)
-{
-  return degree(h,polyhedron);
-}
-*/
 bool Scene_polyhedron_selection_item:: treat_selection(const std::set<fg_edge_descriptor>& selection)
 {
   VPmap vpm = get(CGAL::vertex_point, *polyhedron());
@@ -1203,7 +1220,7 @@ bool Scene_polyhedron_selection_item:: treat_selection(const std::set<fg_edge_de
 
       break;
       //Add vertex and face to border
-    case 9:
+    case 10:
     {
       static fg_halfedge_descriptor t;
       if(!d->first_selected)
@@ -1255,7 +1272,7 @@ bool Scene_polyhedron_selection_item:: treat_selection(const std::set<fg_edge_de
       break;
     }
       //Add face to border
-    case 10:
+    case 11:
     {
       static fg_halfedge_descriptor t;
       if(!d->first_selected)

Lab/demo/Lab/Scene_surface_mesh_item.cpp

@@ -545,15 +545,15 @@ void Scene_surface_mesh_item_priv::compute_elements(Scene_item_rendering_helper:
         }
         if(name.testFlag(Scene_item_rendering_helper::NORMALS))
         {
-          EPICK::Vector_3 n = fnormals[fd];
+          const EPICK::Vector_3& n = fnormals[fd];
           CPF::add_normal_in_buffer(n, flat_normals);
         }
         if(name.testFlag(Scene_item_rendering_helper::COLORS))
         {
           if(has_fpatch_id)
           {
             //The sharp features detection produces patch ids >=1, this
-            //is meant to insure the wanted id is in the range [min,max]
+            //is meant to ensure the wanted id is in the range [min,max]
             QColor c = item->color_vector()[fpatch_id_map[fd] - min_patch_id];
             CGAL::IO::Color color(c.red(),c.green(),c.blue());
             CPF::add_color_in_buffer(color, f_colors);