From 46e771534d64574a347aaf321c23f0fcbda1d991 Mon Sep 17 00:00:00 2001
From: Jane Tournois <janetournois@users.noreply.github.com>
Date: Tue, 21 Nov 2023 16:53:46 +0100
Subject: [PATCH] add example

---
 .../mesh_and_remesh_with_adaptive_sizing.cpp  | 94 +++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 Tetrahedral_remeshing/examples/Tetrahedral_remeshing/mesh_and_remesh_with_adaptive_sizing.cpp

diff --git a/Tetrahedral_remeshing/examples/Tetrahedral_remeshing/mesh_and_remesh_with_adaptive_sizing.cpp b/Tetrahedral_remeshing/examples/Tetrahedral_remeshing/mesh_and_remesh_with_adaptive_sizing.cpp
new file mode 100644
index 000000000000..125c088b1473
--- /dev/null
+++ b/Tetrahedral_remeshing/examples/Tetrahedral_remeshing/mesh_and_remesh_with_adaptive_sizing.cpp
@@ -0,0 +1,94 @@
+#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
+
+#include <CGAL/Polyhedron_3.h>
+#include <CGAL/Polyhedral_mesh_domain_3.h>
+
+#include <CGAL/Mesh_triangulation_3.h>
+#include <CGAL/Mesh_complex_3_in_triangulation_3.h>
+#include <CGAL/Mesh_criteria_3.h>
+#include <CGAL/make_mesh_3.h>
+
+#include <CGAL/tetrahedral_remeshing.h>
+#include <CGAL/Tetrahedral_remeshing/Adaptive_remeshing_sizing_field.h>
+
+#include <CGAL/IO/File_medit.h>
+
+// Domain
+using K = CGAL::Exact_predicates_inexact_constructions_kernel;
+using Point = K::Point_3;
+using FT = K::FT;
+using Polyhedron = CGAL::Polyhedron_3<K>;
+using Mesh_domain = CGAL::Polyhedral_mesh_domain_3<Polyhedron, K>;
+
+// Triangulation for Meshing
+using Tr = CGAL::Mesh_triangulation_3<Mesh_domain>::type;
+using C3t3 = CGAL::Mesh_complex_3_in_triangulation_3<Tr>;
+
+// Criteria
+using Mesh_criteria = CGAL::Mesh_criteria_3<Tr>;
+
+// Triangulation for Remeshing
+using T3 = CGAL::Triangulation_3<Tr::Geom_traits,
+                                 Tr::Triangulation_data_structure>;
+
+// To avoid verbose function and named parameters call
+using namespace CGAL::parameters;
+
+int main(int argc, char* argv[])
+{
+  const std::string fname = (argc > 1) ? argv[1] : CGAL::data_file_path("meshes/elk.off");
+  std::ifstream input(fname);
+  Polyhedron polyhedron;
+  input >> polyhedron;
+  if (input.fail()) {
+    std::cerr << "Error: Cannot read file " << fname << std::endl;
+    return EXIT_FAILURE;
+  }
+
+  if (!CGAL::is_triangle_mesh(polyhedron)) {
+    std::cerr << "Input geometry is not triangulated." << std::endl;
+    return EXIT_FAILURE;
+  }
+
+  // Create domain
+  Mesh_domain domain(polyhedron);
+
+  std::cout << "Meshing...";
+  std::cout.flush();
+
+  // Mesh criteria
+  Mesh_criteria criteria(facet_angle = 25,
+                         facet_distance = 0.2,
+                         cell_radius_edge_ratio = 3);
+
+  // Mesh generation
+  C3t3 c3t3 = CGAL::make_mesh_3<C3t3>(domain, criteria, no_perturb().no_exude());
+
+  std::cout << "\rMeshing done." << std::endl;
+
+  T3 tr = CGAL::convert_to_triangulation_3(std::move(c3t3));
+  //note we use the move semantic, with std::move(c3t3),
+  //  to avoid a copy of the triangulation by the function
+  //  `CGAL::convert_to_triangulation_3()`
+  //  After the call to this function, c3t3 is an empty and valid C3t3.
+  //It is possible to use :  CGAL::convert_to_triangulation_3(c3t3),
+  //  Then the triangulation is copied and duplicated, and c3t3 remains as is.
+
+  std::cout << "Remeshing...";
+  std::cout.flush();
+
+  CGAL::Tetrahedral_remeshing::Adaptive_remeshing_sizing_field<T3>
+    adaptive_field(tr);
+
+  CGAL::tetrahedral_isotropic_remeshing(tr,
+    adaptive_field,
+    CGAL::parameters::number_of_iterations(5));
+
+  std::cout << "\rRemeshing done." << std::endl;
+
+  std::ofstream osr("out_remeshing.mesh");
+  CGAL::IO::write_MEDIT(osr, tr);
+  osr.close();
+
+  return EXIT_SUCCESS;
+}