From: Marco Feder <marco.feder@sissa.it>
Date: Mon, 9 May 2022 22:04:34 +0000 (+0200)
Subject: Convert CGAL::Surface_mesh to coarse mesh
X-Git-Tag: v9.4.0-rc1~219^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F13705%2Fhead;p=dealii.git

Convert CGAL::Surface_mesh to coarse mesh
---

diff --git a/cmake/config/template-arguments.in b/cmake/config/template-arguments.in
index 4a9cc4aab1..a4231884ba 100644
--- a/cmake/config/template-arguments.in
+++ b/cmake/config/template-arguments.in
@@ -279,6 +279,5 @@ OUTPUT_FLAG_TYPES := { DXFlags; UcdFlags; GnuplotFlags; PovrayFlags; EpsFlags;
                        Deal_II_IntermediateFlags }
 
 // CGAL Kernels
-CGAL_KERNELS := {CGAL::Simple_cartesian<double>; CGAL::Exact_predicates_exact_constructions_kernel;
-                CGAL::Exact_predicates_exact_constructions_kernel_with_sqrt; 
+CGAL_KERNELS := {CGAL::Simple_cartesian<double>; CGAL::Exact_predicates_exact_constructions_kernel; 
                 CGAL::Exact_predicates_inexact_constructions_kernel }
diff --git a/include/deal.II/cgal/utilities.h b/include/deal.II/cgal/utilities.h
index 930ed2247a..b26cb32454 100644
--- a/include/deal.II/cgal/utilities.h
+++ b/include/deal.II/cgal/utilities.h
@@ -20,10 +20,23 @@
 
 #ifdef DEAL_II_WITH_CGAL
 #  include <CGAL/Cartesian.h>
+#  include <CGAL/Complex_2_in_triangulation_3.h>
 #  include <CGAL/Exact_predicates_exact_constructions_kernel.h>
-#  include <CGAL/Exact_predicates_exact_constructions_kernel_with_sqrt.h>
 #  include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
+#  include <CGAL/Kernel_traits.h>
+#  include <CGAL/Mesh_complex_3_in_triangulation_3.h>
+#  include <CGAL/Mesh_criteria_3.h>
+#  include <CGAL/Mesh_triangulation_3.h>
+#  include <CGAL/Polygon_mesh_processing/triangulate_faces.h>
+#  include <CGAL/Polyhedral_mesh_domain_with_features_3.h>
 #  include <CGAL/Simple_cartesian.h>
+#  include <CGAL/Surface_mesh.h>
+#  include <CGAL/Triangulation_3.h>
+#  include <CGAL/make_mesh_3.h>
+#  include <CGAL/make_surface_mesh.h>
+
+#  include <type_traits>
+
 
 
 DEAL_II_NAMESPACE_OPEN
@@ -41,6 +54,12 @@ DEAL_II_NAMESPACE_OPEN
  */
 namespace CGALWrappers
 {
+#  ifdef CGAL_CONCURRENT_MESH_3
+  using ConcurrencyTag = CGAL::Parallel_tag;
+#  else
+  using ConcurrencyTag = CGAL::Sequential_tag;
+#  endif
+
   /**
    * Convert from deal.II Point to any compatible CGAL point.
    *
@@ -64,6 +83,26 @@ namespace CGALWrappers
   template <int dim, typename CGALPointType>
   inline dealii::Point<dim>
   cgal_point_to_dealii_point(const CGALPointType &p);
+
+  /**
+   * Given a closed CGAL::Surface_mesh, this function fills the
+   * region bounded by the surface with tets, keeping them as coarse as
+   * possible.
+   *
+   * The number of the generated tetrahedrons depends on the refinement level of
+   * surface mesh. This function does not attempt to construct a fine
+   * triangulation, nor to smooth the final result. If you need finer control on
+   * the resulting triangulation, you should consider using directly
+   * CGAL::make_mesh_3().
+   *
+   * @param [in] surface_mesh The (closed) surface mesh bounding the volume that has to be filled.
+   * @param [out] triangulation The output triangulation filled with tetrahedra.
+   */
+  template <typename C3t3>
+  void
+  cgal_surface_mesh_to_cgal_coarse_triangulation(
+    CGAL::Surface_mesh<typename C3t3::Point::Point> &surface_mesh,
+    C3t3 &                                           triangulation);
 } // namespace CGALWrappers
 
 #  ifndef DOXYGEN
@@ -106,6 +145,37 @@ namespace CGALWrappers
     else
       Assert(false, dealii::ExcNotImplemented());
   }
+
+
+
+  template <typename C3t3>
+  void
+  cgal_surface_mesh_to_cgal_coarse_triangulation(
+    CGAL::Surface_mesh<typename C3t3::Point::Point> &surface_mesh,
+    C3t3 &                                           triangulation)
+  {
+    using CGALPointType = typename C3t3::Point::Point;
+    Assert(CGAL::is_closed(surface_mesh),
+           ExcMessage("The surface mesh must be closed."));
+
+    using K           = typename CGAL::Kernel_traits<CGALPointType>::Kernel;
+    using Mesh_domain = CGAL::Polyhedral_mesh_domain_with_features_3<
+      K,
+      CGAL::Surface_mesh<CGALPointType>>;
+    using Tr = typename CGAL::
+      Mesh_triangulation_3<Mesh_domain, CGAL::Default, ConcurrencyTag>::type;
+    using Mesh_criteria = CGAL::Mesh_criteria_3<Tr>;
+
+    CGAL::Polygon_mesh_processing::triangulate_faces(surface_mesh);
+    Mesh_domain domain(surface_mesh);
+    domain.detect_features();
+    Mesh_criteria criteria;
+    // Mesh generation
+    triangulation = CGAL::make_mesh_3<C3t3>(domain,
+                                            criteria,
+                                            CGAL::parameters::no_perturb(),
+                                            CGAL::parameters::no_exude());
+  }
 } // namespace CGALWrappers
 #  endif
 
diff --git a/tests/cgal/cgal_surface_mesh_02.cc b/tests/cgal/cgal_surface_mesh_02.cc
new file mode 100644
index 0000000000..f9a1d228d1
--- /dev/null
+++ b/tests/cgal/cgal_surface_mesh_02.cc
@@ -0,0 +1,74 @@
+// ---------------------------------------------------------------------
+//
+// Copyright (C) 2022 by the deal.II authors
+//
+// This file is part of the deal.II library.
+//
+// The deal.II library is free software; you can use it, redistribute
+// it, and/or modify it under the terms of the GNU Lesser General
+// Public License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+// The full text of the license can be found in the file LICENSE.md at
+// the top level directory of deal.II.
+//
+// ---------------------------------------------------------------------
+
+// Read a Surface_mesh from an .off file, then create a coarse mesh filled with
+// tets
+
+#include <deal.II/base/config.h>
+
+#include <deal.II/grid/grid_generator.h>
+#include <deal.II/grid/tria.h>
+
+#include <CGAL/IO/File_medit.h>
+#include <CGAL/IO/io.h>
+#include <deal.II/cgal/utilities.h>
+
+#include "../tests.h"
+
+// Create a Surface_mesh from an .off file, then fill it with tets and print
+// vertices.
+
+using K         = CGAL::Exact_predicates_inexact_constructions_kernel;
+using CGALPoint = CGAL::Point_3<K>;
+using namespace CGALWrappers;
+using Mesh_domain =
+  CGAL::Polyhedral_mesh_domain_with_features_3<K,
+                                               CGAL::Surface_mesh<CGALPoint>>;
+using Tr = typename CGAL::
+  Mesh_triangulation_3<Mesh_domain, CGAL::Default, ConcurrencyTag>::type;
+using Mesh_criteria = CGAL::Mesh_criteria_3<Tr>;
+using C3t3          = CGAL::Mesh_complex_3_in_triangulation_3<Tr,
+                                                     Mesh_domain::Corner_index,
+                                                     Mesh_domain::Curve_index>;
+
+void
+test()
+{
+  const std::vector<std::string> fnames{"input_grids/cube.off",
+                                        "input_grids/tetrahedron.off"};
+  CGAL::Surface_mesh<CGALPoint>  sm;
+  C3t3                           tria;
+  for (const auto &name : fnames)
+    {
+      std::ifstream input(name);
+      input >> sm;
+      cgal_surface_mesh_to_cgal_coarse_triangulation(sm, tria);
+      {
+        std::ofstream off_file_medit("coarse.mesh");
+        tria.output_to_medit(off_file_medit, false);
+      }
+      cat_file("coarse.mesh");
+      sm.clear(); // reset surface
+      tria.clear();
+      deallog << std::endl << std::endl;
+    }
+}
+
+int
+main()
+{
+  initlog();
+  test();
+}
diff --git a/tests/cgal/cgal_surface_mesh_02.output b/tests/cgal/cgal_surface_mesh_02.output
new file mode 100644
index 0000000000..8330e7b04e
--- /dev/null
+++ b/tests/cgal/cgal_surface_mesh_02.output
@@ -0,0 +1,407 @@
+
+MeshVersionFormatted 1
+Dimension 3
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+End
+
+DEAL::
+DEAL::
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+End
+
+DEAL::
+DEAL::
diff --git a/tests/cgal/input_grids/cube.off b/tests/cgal/input_grids/cube.off
new file mode 100644
index 0000000000..e200aa44bd
--- /dev/null
+++ b/tests/cgal/input_grids/cube.off
@@ -0,0 +1,22 @@
+OFF
+8 12 0
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\ No newline at end of file
diff --git a/tests/cgal/input_grids/tetrahedron.off b/tests/cgal/input_grids/tetrahedron.off
new file mode 100644
index 0000000000..9e02601667
--- /dev/null
+++ b/tests/cgal/input_grids/tetrahedron.off
@@ -0,0 +1,11 @@
+OFF
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+
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