MaelRL · Feb 17, 2026 · Feb 17, 2026 · Feb 17, 2026 · Feb 17, 2026 · Feb 17, 2026
diff --git a/Constrained_triangulation_3/include/CGAL/Conforming_constrained_Delaunay_triangulation_3.h b/Constrained_triangulation_3/include/CGAL/Conforming_constrained_Delaunay_triangulation_3.h
diff --git a/..._triangulation_3/include/CGAL/Conforming_constrained_Delaunay_triangulation_cell_base_3.h b/..._triangulation_3/include/CGAL/Conforming_constrained_Delaunay_triangulation_cell_base_3.h
@@ -70,9 +70,9 @@ class Conforming_constrained_Delaunay_triangulation_cell_base_3
   }
 
   static std::string io_signature() {
-    static_assert(
-        std::is_same_v<
-            decltype(std::declval<Conforming_constrained_Delaunay_triangulation_cell_data_3>().face_constraint_index(0)), int>);
+//    static_assert(
+//        std::is_same_v<
+//            decltype(std::declval<Conforming_constrained_Delaunay_triangulation_cell_data_3>().face_constraint_index(0)), int>);
 
     return Get_io_signature<Base>()() + "+(" + Get_io_signature<int>()() + ")[4]";
   }
@@ -82,13 +82,13 @@ class Conforming_constrained_Delaunay_triangulation_cell_base_3
              const Conforming_constrained_Delaunay_triangulation_cell_base_3& c)
   {
     os << static_cast<const Base&>(c);
-    for( unsigned li = 0; li < 4; ++li ) {
-      if(IO::is_ascii(os)) {
-        os << " " << c.ccdt_3_data().face_constraint_index(li);
-      } else {
-        CGAL::write(os, c.ccdt_3_data().face_constraint_index(li));
-      }
-    }
+    //for( unsigned li = 0; li < 4; ++li ) {
+    //  if(IO::is_ascii(os)) {
+    //    os << " " << face_constraint_index(c, li);
+    //  } else {
+    //    CGAL::write(os, face_constraint_index(c, li));
+    //  }
+    //}
     return os;
   }
   friend std::istream&
@@ -97,16 +97,16 @@ class Conforming_constrained_Delaunay_triangulation_cell_base_3
   {
     is >> static_cast<Base&>(c);
     if(!is) return is;
-    for( int li = 0; li < 4; ++li ) {
-      int i;
-      if(IO::is_ascii(is)) {
-        is >> i;
-      } else {
-        CGAL::read(is, i);
-      }
-      if(!is) return is;
-      c->ccdt_3_data().set_face_constraint_index(li, i);
-    }
+//    for( int li = 0; li < 4; ++li ) {
+//      int i;
+//      if(IO::is_ascii(is)) {
+//        is >> i;
+//      } else {
+//        CGAL::read(is, i);
+//      }
+//      if(!is) return is;
+//      set_face_constraint_index(c, li, i);
+//    }
     return is;
   }
 };

diff --git a/..._triangulation_3/include/CGAL/Conforming_constrained_Delaunay_triangulation_cell_data_3.h b/..._triangulation_3/include/CGAL/Conforming_constrained_Delaunay_triangulation_cell_data_3.h
@@ -42,8 +42,6 @@ class Conforming_constrained_Delaunay_triangulation_cell_data_3 {
   template <typename Tr> friend class Conforming_constrained_Delaunay_triangulation_3_impl;
   /// @endcond
 
-  std::array<CDT_3_signed_index, 4> face_id = { -1, -1, -1, -1 };
-  std::array<void*, 4> facet_2d = {nullptr, nullptr, nullptr, nullptr};
   std::bitset<static_cast<unsigned>(CDT_3_cell_marker::nb_of_markers)> markers;
 
   bool is_marked() const { return markers.any(); }
@@ -52,35 +50,6 @@ class Conforming_constrained_Delaunay_triangulation_cell_data_3 {
   void clear_mark(CDT_3_cell_marker m) { markers.reset(static_cast<unsigned>(m)); }
   void clear_marks() { markers.reset(); }
 
-  static unsigned int uint(int i) { return static_cast<unsigned int>(i); }
-
-  template <typename Facet_handle>
-  void set_facet_constraint(int i, CDT_3_signed_index face_id,
-                            Facet_handle facet_2d)
-  {
-    this->face_id[uint(i)] = face_id;
-    this->facet_2d[uint(i)] = static_cast<void*>(facet_2d == Facet_handle{} ?  nullptr : std::addressof(*facet_2d));
-  }
-
-  template <typename CDT_2>
-  auto face_2 (const CDT_2& cdt, int i) const {
-    using Face = typename CDT_2::Face;
-    auto ptr = static_cast<Face*>(facet_2d[uint(i)]);
-    return cdt.tds().faces().iterator_to(*ptr);
-  }
-public:
-  /// @{
-  // @cond SKIP_IN_MANUAL
-  bool is_facet_constrained(int i) const { return face_id[uint(i)] >= 0; }
-
-  CDT_3_signed_index face_constraint_index(int i) const {
-    return face_id[uint(i)];
-  }
-
-  void set_face_constraint_index(int i, CDT_3_signed_index index) {
-    face_id[uint(i)] = index;
-  }
-  /// @endcond
 };
 
 } // namespace CGAL

diff --git a/Constrained_triangulation_3/include/CGAL/IO/write_MEDIT.h b/Constrained_triangulation_3/include/CGAL/IO/write_MEDIT.h
@@ -95,8 +95,10 @@ void write_MEDIT(std::ostream& os,
   const bool has_plc_face_id
     = choose_parameter(get_parameter(np, internal_np::with_plc_face_id), false);
 
-  auto plc_patch_map = boost::make_function_property_map<Facet>([&](const Facet& f)
-    { return has_plc_face_id ? f.first->ccdt_3_data().face_constraint_index(f.second) + 1 : 1; });
+  auto plc_patch_map = boost::make_function_property_map<Facet>([&](const Facet& f) {
+    return has_plc_face_id
+         ? ccdt.face_constraint_index(f.first, f.second) + 1
+         : 1; });
 
   std::vector<typename Tr_::Edge> edges;
   return SMDS_3::output_to_medit(os,

diff --git a/Constrained_triangulation_3/include/CGAL/draw_constrained_triangulation_3.h b/Constrained_triangulation_3/include/CGAL/draw_constrained_triangulation_3.h
@@ -15,6 +15,7 @@
 #include <CGAL/license/Constrained_triangulation_3.h>
 #include <CGAL/draw_triangulation_3.h>
 #include <CGAL/Conforming_constrained_Delaunay_triangulation_3_fwd.h>
+#include <CGAL/Constrained_triangulation_3_types.h>
 #include <CGAL/type_traits.h>
 #include <algorithm>
 
@@ -34,35 +35,33 @@ void draw(const Conforming_constrained_Delaunay_triangulation_3<Traits, Tr>& ccd
 {
   using Tr_ = CGAL::cpp20::remove_cvref_t<decltype(ccdt.triangulation())>;
   using Vertex_handle = typename Tr_::Vertex_handle;
-  using Cell_handle = typename Tr_::Cell_handle;
   using Edge_descriptor = typename Tr_::Finite_edges_iterator;
   using Facet_descriptor = typename Tr_::Finite_facets_iterator;
 
-  using Face_index = CGAL::cpp20::remove_cvref_t<
-      decltype(std::declval<Cell_handle>()->ccdt_3_data().face_constraint_index(0))>;
+  using Face_index = CDT_3_signed_index;
 
   Face_index nb_colors = 0;
   std::for_each(
       ccdt.constrained_facets_begin(), ccdt.constrained_facets_end(),
       [&](const auto& f) {
         auto [c, index] = f;
-        nb_colors = (std::max)(nb_colors, c->ccdt_3_data().face_constraint_index(index) + 1);
+        nb_colors = (std::max)(nb_colors, ccdt.face_constraint_index(c, index) + 1);
       });
   std::vector<CGAL::IO::Color> colors(nb_colors);
   std::generate(colors.begin(), colors.end(), []() {
     return CGAL::get_random_color(CGAL::get_default_random());
   });
   CGAL::Graphics_scene_options<Tr_, Vertex_handle, Edge_descriptor, Facet_descriptor> options;
-  options.draw_face = [](const Tr_&, Facet_descriptor f) {
+  options.draw_face = [&](const Tr_&, Facet_descriptor f) {
     auto [c, index] = *f;
-    return c->ccdt_3_data().is_facet_constrained(index);
+    return ccdt.is_facet_constrained(c, index);
   };
   options.colored_face = [](const Tr_&, Facet_descriptor) {
     return true;
   };
   options.face_color = [&](const Tr_&, Facet_descriptor f) {
     auto [c, index] = *f;
-    return colors[c->ccdt_3_data().face_constraint_index(index)];
+    return colors[ccdt.face_constraint_index(c, index)];
   };
   draw(ccdt.triangulation(), options, title);
 }

diff --git a/Constrained_triangulation_3/test/Constrained_triangulation_3/cdt_3_from_off.cpp b/Constrained_triangulation_3/test/Constrained_triangulation_3/cdt_3_from_off.cpp
@@ -386,7 +386,7 @@ std::function<void()> create_output_finalizer(const CDT& cdt, const CDT_options&
         cells_map[ch] = 0;
         for (int i = 0; i < 4; ++i)
         {
-          if(ch->ccdt_3_data().is_facet_constrained(i))
+          if(cdt.is_facet_constrained(ch, i))
             continue;
           auto n = ch->neighbor(i);
           if (cells_map[n] == 1)

diff --git a/Generator/examples/Generator/random_points_in_tetrahedral_mesh_3.cpp b/Generator/examples/Generator/random_points_in_tetrahedral_mesh_3.cpp
@@ -32,7 +32,7 @@ typedef CGAL::Mesh_triangulation_3<
 typedef CGAL::Mesh_complex_3_in_triangulation_3<Tr>               C3t3;
 
 // Criteria
-typedef CGAL::Mesh_criteria_3<Tr>                                 Mesh_criteria;
+typedef CGAL::Mesh_criteria_3<C3t3>                               Mesh_criteria;
 
 // (Unweighted) point type
 typedef Tr::Bare_point                                            Point;

diff --git a/Generator/examples/Generator/random_points_on_tetrahedral_mesh_3.cpp b/Generator/examples/Generator/random_points_on_tetrahedral_mesh_3.cpp
@@ -31,7 +31,7 @@ typedef CGAL::Mesh_triangulation_3<
 typedef CGAL::Mesh_complex_3_in_triangulation_3<Tr>               C3t3;
 
 // Criteria
-typedef CGAL::Mesh_criteria_3<Tr>                                 Mesh_criteria;
+typedef CGAL::Mesh_criteria_3<C3t3>                               Mesh_criteria;
 
 // (Unweighted) point type
 typedef Tr::Bare_point                                            Point;

diff --git a/Generator/test/Generator/generic_random_test.cpp b/Generator/test/Generator/generic_random_test.cpp
@@ -55,7 +55,7 @@ typedef Mesh_domain::Curve_index                                  Curve_index;
 typedef CGAL::Mesh_triangulation_3<Mesh_domain>::type             Tr;
 typedef CGAL::Mesh_complex_3_in_triangulation_3<
           Tr, Corner_index, Curve_index>                          C3t3;
-typedef CGAL::Mesh_criteria_3<Tr>                                 Mesh_criteria;
+typedef CGAL::Mesh_criteria_3<C3t3>                               Mesh_criteria;
 typedef C3t3::Point                                               Point;
 
 int test_triangles_2(const FT eps)

diff --git a/Installation/CHANGES.md b/Installation/CHANGES.md
@@ -46,6 +46,15 @@ Release date: December 2026
 - Deprecated the existing overload of `snap_rounding_2()`.
 - Added a new overload of `snap_rounding_2()` that automatically dispatch to either `vertical_slab_snap_rounding_2()` or `hot_pixel_snap_rounding_2()`, depending on the provided traits class.
 
+### [3D Mesh Generation](https://doc.cgal.org/6.3/Manual/packages.html#PkgMesh3)
+
+- **Breaking change**: The template parameter of `CGAL::Mesh_cell_criteria_3`,
+  `CGAL::Mesh_edge_criteria_3`, and `CGAL::Mesh_facet_criteria_3` is now the
+  mesh complex type `C3T3`, rather than its triangulation type. Code that
+  explicitly instantiates these criteria classes must be updated accordingly.
+  `CGAL::Mesh_criteria_3` also uses `C3T3` as its template parameter, but
+  continues to accept the triangulation type for backward compatibility.
+
 ### [3D Triangulations](https://doc.cgal.org/6.3/Manual/packages.html#PkgTriangulation3)
 - **Breaking change** Removed the class template `Regular_triangulation_euclidean_traits_3` which was deprecated  since CGAL-4.10
 - **Breaking change** Removed the member function `vertices_in_conflict()` of the Delaunay and the regular triangulation  which were deprecated  since CGAL-3.8

diff --git a/Installation/include/CGAL/Mesh_3/Mesh_complex_3_in_triangulation_3_fwd.h b/Installation/include/CGAL/Mesh_3/Mesh_complex_3_in_triangulation_3_fwd.h
@@ -24,14 +24,14 @@ template <typename Tr,
           typename CurveIndex = int>
 class Mesh_complex_3_in_triangulation_3;
 
-template<class Tr, bool c3t3_loader_failed>
-bool build_triangulation_from_file(std::istream& is,
-                                   Tr& tr,
-                                   bool replace_domain_0);
-
-template<class Tr, bool c3t3_loader_failed>
-bool build_triangulation_from_file(std::istream& is,
-                                   Tr& tr);
+template <class C3T3, bool c3t3_loader_failed>
+bool build_mesh_complex_from_file(std::istream& is,
+                                  C3T3& c3t3,
+                                  bool replace_domain_0);
+
+template <class C3T3, bool c3t3_loader_failed>
+bool build_mesh_complex_from_file(std::istream& is,
+                                  C3T3& c3t3);
 } // CGAL
 #endif
 

diff --git a/Installation/include/CGAL/SMDS_3/Mesh_complex_3_in_triangulation_3_fwd.h b/Installation/include/CGAL/SMDS_3/Mesh_complex_3_in_triangulation_3_fwd.h
@@ -51,6 +51,16 @@ bool build_triangulation_from_file(std::istream& is,
                                    const bool allow_negative_orientation = false,
                                    CxEdgesOutputIterator cx_edges_oit = CxEdgesOutputIterator());
 
+template <class C3T3,
+          class CxEdgesOutputIterator = CGAL::Emptyset_iterator>
+bool build_mesh_complex_from_file(std::istream& is,
+                                   C3T3& c3t3,
+                                   const bool verbose = false,
+                                   const bool replace_domain_0 = false,
+                                   const bool allow_non_manifold = false,
+                                   const bool allow_negative_orientation = false,
+                                   CxEdgesOutputIterator cx_edges_oit = CxEdgesOutputIterator());
+
 } // namespace SMDS_3
 } // namespace CGAL
 #endif

diff --git a/Lab/demo/Lab/Plugins/IO/VTK_io_plugin.cpp b/Lab/demo/Lab/Plugins/IO/VTK_io_plugin.cpp
@@ -40,6 +40,7 @@
 #include <CGAL/IO/output_to_vtu.h>
 #include <CGAL/boost/graph/IO/VTK.h>
 #include <CGAL/IO/VTK.h>
+#include <CGAL/iterator.h>
 
 #include <vtkSmartPointer.h>
 #include <vtkDataSetReader.h>
@@ -428,7 +429,7 @@ class CGAL_Lab_vtk_plugin :
         subdomains.push_back(si);
       }
       std::map<Facet, int> border_facets;
-      //Preprocessing for build_triangulation
+      //Preprocessing for build_mesh_complex
       //check for orientation and swap in cells if not good.
       for(std::size_t i=0; i<finite_cells.size(); ++i)
       {
@@ -447,12 +448,14 @@ class CGAL_Lab_vtk_plugin :
 
       std::vector<std::array<int, 3>> feature_edges;
       std::vector<std::array<int, 2>> corners;
+      std::vector<Tr::Vertex_handle> vertex_handle_vector;
 
-      CGAL::SMDS_3::build_triangulation_with_subdomains_range(
-        c3t3_item->c3t3().triangulation(),
+      CGAL::SMDS_3::build_mesh_complex_with_subdomains_range(
+        c3t3_item->c3t3(),
         points, finite_cells, subdomains, border_facets,
         feature_edges, corners,
-        CGAL::Emptyset_iterator(),
+        vertex_handle_vector,
+        CGAL::Emptyset_iterator{},
         false, false, true, true);
 
       for( C3t3::Triangulation::Finite_cells_iterator
@@ -464,9 +467,9 @@ class CGAL_Lab_vtk_plugin :
           c3t3_item->c3t3().add_to_complex(cit, cit->info());
         for(int i=0; i < 4; ++i)
         {
-          if(cit->surface_patch_index(i)>0)
+          if(c3t3_item->c3t3().surface_patch_index(cit, i) > 0)
           {
-            c3t3_item->c3t3().add_to_complex(cit, i, cit->surface_patch_index(i));
+            c3t3_item->c3t3().add_to_complex(cit, i, c3t3_item->c3t3().surface_patch_index(cit, i));
           }
         }
       }
@@ -485,11 +488,11 @@ class CGAL_Lab_vtk_plugin :
           Cell_handle nc = c->neighbor(fit->second);
 
           // By definition, Subdomain_index() is supposed to be the id of the exterior
-          if(c->subdomain_index() != C3t3::Triangulation::Cell::Subdomain_index() &&
-             nc->subdomain_index() == C3t3::Triangulation::Cell::Subdomain_index())
+          if(c3t3_item->c3t3().subdomain_index(c) != C3t3::Subdomain_index() &&
+             c3t3_item->c3t3().subdomain_index(nc) == C3t3::Subdomain_index())
           {
             // Color the border facet with the index of its cell
-            c3t3_item->c3t3().add_to_complex(c, fit->second, c->subdomain_index());
+            c3t3_item->c3t3().add_to_complex(c, fit->second, c3t3_item->c3t3().subdomain_index(c));
           }
         }
       }

diff --git a/Lab/demo/Lab/Plugins/Mesh_3/C3t3_io_plugin.cpp b/Lab/demo/Lab/Plugins/Mesh_3/C3t3_io_plugin.cpp
@@ -167,7 +167,7 @@ CGAL_Lab_c3t3_binary_io_plugin::load(
 
       item->setName(fileinfo.completeBaseName());
 
-      if (CGAL::IO::read_AVIZO_TETRA(in, item->c3t3().triangulation()))
+      if (CGAL::IO::read_AVIZO_TETRA(in, item->c3t3()))
       {
         update_c3t3(item->c3t3());
 
@@ -449,14 +449,14 @@ update_c3t3(C3t3& c3t3)
   c3t3.rescan_after_load_of_triangulation(); //fix counters for facets and cells
   for (Cell_handle cit : c3t3.triangulation().finite_cell_handles())
   {
-    CGAL_assertion(cit->subdomain_index() >= 0);
-    if (cit->subdomain_index() != C3t3::Triangulation::Cell::Subdomain_index())
-      c3t3.add_to_complex(cit, cit->subdomain_index());
+    CGAL_assertion(c3t3.subdomain_index(cit) >= 0);
+    if (c3t3.subdomain_index(cit) != C3t3::Subdomain_index())
+      c3t3.add_to_complex(cit, c3t3.subdomain_index(cit));
 
     for (int i = 0; i < 4; ++i)
     {
-      if (cit->surface_patch_index(i) > 0)
-        c3t3.add_to_complex(cit, i, cit->surface_patch_index(i));
+      if (c3t3.surface_patch_index(cit, i) > 0)
+        c3t3.add_to_complex(cit, i, c3t3.surface_patch_index(cit, i));
     }
   }
 
@@ -469,11 +469,11 @@ update_c3t3(C3t3& c3t3)
       Cell_handle nc = c->neighbor(fit.second);
 
       // By definition, Subdomain_index() is supposed to be the id of the exterior
-      if (c->subdomain_index() != C3t3::Triangulation::Cell::Subdomain_index() &&
-          nc->subdomain_index() == C3t3::Triangulation::Cell::Subdomain_index())
+      if (c3t3.subdomain_index(c) != C3t3::Subdomain_index() &&
+          c3t3.subdomain_index(nc) == C3t3::Subdomain_index())
       {
         // Color the border facet with the index of its cell
-        c3t3.add_to_complex(c, fit.second, c->subdomain_index());
+        c3t3.add_to_complex(c, fit.second, c3t3.subdomain_index(c));
       }
     }
   }