add an option to not refine one of the two meshes

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

@@ -101,6 +101,7 @@ CGAL_add_named_parameter(area_threshold_t, area_threshold, area_threshold)
 CGAL_add_named_parameter(halfedges_keeper_t, halfedges_keeper, halfedges_keeper)
 CGAL_add_named_parameter(volume_threshold_t, volume_threshold, volume_threshold)
 CGAL_add_named_parameter(dry_run_t, dry_run, dry_run)
+CGAL_add_named_parameter(do_not_modify_t, do_not_modify, do_not_modify)
 
 // List of named parameters that we use in the package 'Surface Mesh Simplification'
 CGAL_add_named_parameter(get_cost_policy_t, get_cost_policy, get_cost)

BGL/test/BGL/test_cgal_bgl_named_params.cpp

@@ -97,6 +97,7 @@ void test(const NamedParameters& np)
   assert(get_parameter(np, CGAL::internal_np::do_lock_mesh).v == 61);
   assert(get_parameter(np, CGAL::internal_np::halfedges_keeper).v == 62);
   assert(get_parameter(np, CGAL::internal_np::do_simplify_border).v == 64);
+  assert(get_parameter(np, CGAL::internal_np::do_not_modify).v == 65);
   assert(get_parameter(np, CGAL::internal_np::maximum_number_of_faces).v == 78910);
 
     // Named parameters that we use in the package 'Surface Mesh Simplification'
@@ -184,6 +185,7 @@ void test(const NamedParameters& np)
   check_same_type<54>(get_parameter(np, CGAL::internal_np::use_area_smoothing));
   check_same_type<55>(get_parameter(np, CGAL::internal_np::use_Delaunay_flips));
   check_same_type<56>(get_parameter(np, CGAL::internal_np::use_safety_constraints));
+  check_same_type<65>(get_parameter(np, CGAL::internal_np::do_not_modify));
 
   check_same_type<12340>(get_parameter(np, CGAL::internal_np::do_self_intersection_tests));
   check_same_type<12341>(get_parameter(np, CGAL::internal_np::do_orientation_tests));
@@ -353,6 +355,7 @@ int main()
                          .halfedges_keeper(A<62>(62))
                          .use_convex_hull(A<63>(63))
                          .do_simplify_border(A<64>(64))
+			 .do_not_modify(A<65>(65))
                          .point_map(A<9000>(9000))
                          .query_point_map(A<9001>(9001))
                          .normal_map(A<9002>(9002))

Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/corefinement.h

@@ -626,6 +626,9 @@ corefine_and_compute_difference(      TriangleMesh& tm1,
  *      checked for self-intersection and `CGAL::Polygon_mesh_processing::Corefinement::Self_intersection_exception`
  *      will be thrown if at least one is found (`np1` only).
  *   \cgalParamEnd
+ *   \cgalParamBegin{do_not_modify} if `true`, the corresponding mesh will not be updated. The default value is `false`.
+ *                                  Obviously if this parameter is set to `true` for both meshes nothing will be done.
+ *   \cgalParamEnd
  * \cgalNamedParamsEnd
  *
  */
@@ -641,9 +644,19 @@ corefine(      TriangleMesh& tm1,
   using parameters::choose_parameter;
   using parameters::get_parameter;
 
+  if (choose_parameter(get_parameter(np1, internal_np::do_not_modify), false))
+  {
+    if (choose_parameter(get_parameter(np2, internal_np::do_not_modify), false))
+      return;
+    return corefine(tm2,tm1, np2, np1);
+  }
+
   const bool throw_on_self_intersection =
     choose_parameter(get_parameter(np1, internal_np::throw_on_self_intersection), false);
 
+  const bool modify_tm2 =
+    !choose_parameter(get_parameter(np2, internal_np::do_not_modify), false);
+
 // Vertex point maps
   typedef typename GetVertexPointMap<TriangleMesh,
                                      NamedParameters1>::type Vpm;
@@ -700,7 +713,7 @@ corefine(      TriangleMesh& tm1,
   Ob ob;
   Ecm ecm(tm1,tm2,ecm1,ecm2);
   Corefinement::Intersection_of_triangle_meshes<TriangleMesh, Vpm, Algo_visitor>
-    functor(tm1, tm2, vpm1, vpm2, Algo_visitor(uv,ob,ecm));
+    functor(tm1, tm2, vpm1, vpm2, Algo_visitor(uv,ob,ecm,modify_tm2));
   functor(CGAL::Emptyset_iterator(), throw_on_self_intersection, true);
 }
 

Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Corefinement/Visitor.h

@@ -170,6 +170,7 @@ private:
   OutputBuilder& output_builder;
   EdgeMarkMapBind marks_on_edges;
   bool input_with_coplanar_faces;
+  bool refine_tm2;
 
   template <class Ecm1, class Ecm2>
   void call_put(Ecm_bind<TriangleMesh, Ecm1, Ecm2>& ecm,
@@ -200,12 +201,13 @@ private:
 // visitor public functions
 public:
   Surface_intersection_visitor_for_corefinement(
-    UserVisitor& uv, OutputBuilder& o, const EdgeMarkMapBind& emm)
+    UserVisitor& uv, OutputBuilder& o, const EdgeMarkMapBind& emm, bool refine_tm2=true)
     : number_coplanar_vertices(0)
     , user_visitor(uv)
     , output_builder(o)
     , marks_on_edges(emm)
     , input_with_coplanar_faces(false)
+    , refine_tm2(refine_tm2)
   {}
 
   template<class Graph_node>
@@ -624,6 +626,7 @@ public:
           ++it)
     {
       TriangleMesh& tm=*it->first;
+      if (!refine_tm2 && tm2_ptr==&tm) continue;
     //   Face_boundaries& face_boundaries=mesh_to_face_boundaries[&tm];
 
       Node_to_target_of_hedge_map& nodes_to_hedge=it->second;
@@ -693,6 +696,7 @@ public:
       it=on_edge.begin(); it!=on_edge.end(); ++it)
     {
       TriangleMesh& tm=*it->first;
+      if (!refine_tm2 && tm2_ptr==&tm) continue;
       const VertexPointMap& vpm=vpms[&tm];
       On_edge_map& on_edge_map=it->second;
       On_face_map& on_face_map=on_face[&tm];
@@ -788,6 +792,7 @@ public:
       it=on_face.begin(); it!=on_face.end(); ++it)
     {
       TriangleMesh& tm=*it->first;
+      if (!refine_tm2 && tm2_ptr==&tm) continue;
       const VertexPointMap& vpm=vpms[&tm];
       On_face_map& on_face_map=it->second;
       Face_boundaries& face_boundaries=mesh_to_face_boundaries[&tm];