From e3478fed9857fcffe1618f71c5b0019ef89a10e0 Mon Sep 17 00:00:00 2001
From: Laurent Rineau <laurent.rineau@cgal.org>
Date: Thu, 24 Apr 2025 17:39:24 +0200
Subject: [PATCH] add an example polygon soup with face patch map

---
 .../CMakeLists.txt                            |  4 +-
 ...elaunay_triangulation_3_from_soup_fmap.cpp | 63 +++++++++++++++++++
 2 files changed, 66 insertions(+), 1 deletion(-)
 create mode 100644 Constrained_triangulation_3/examples/Constrained_triangulation_3/conforming_constrained_Delaunay_triangulation_3_from_soup_fmap.cpp

diff --git a/Constrained_triangulation_3/examples/Constrained_triangulation_3/CMakeLists.txt b/Constrained_triangulation_3/examples/Constrained_triangulation_3/CMakeLists.txt
index 6407c040b81..4623aa28260 100644
--- a/Constrained_triangulation_3/examples/Constrained_triangulation_3/CMakeLists.txt
+++ b/Constrained_triangulation_3/examples/Constrained_triangulation_3/CMakeLists.txt
@@ -6,12 +6,14 @@ find_package(CGAL REQUIRED COMPONENTS Qt6)
 create_single_source_cgal_program(conforming_constrained_Delaunay_triangulation_3.cpp)
 create_single_source_cgal_program(conforming_constrained_Delaunay_triangulation_3_fpmap.cpp)
 create_single_source_cgal_program(conforming_constrained_Delaunay_triangulation_3_from_soup.cpp)
+create_single_source_cgal_program(conforming_constrained_Delaunay_triangulation_3_from_soup_fmap.cpp)
 create_single_source_cgal_program(remesh_constrained_Delaunay_triangulation_3.cpp)
 
 if(CGAL_Qt6_FOUND)
   target_link_libraries(conforming_constrained_Delaunay_triangulation_3 PUBLIC CGAL::CGAL_Basic_viewer)
   target_link_libraries(conforming_constrained_Delaunay_triangulation_3_from_soup PUBLIC CGAL::CGAL_Basic_viewer)
+  target_link_libraries(conforming_constrained_Delaunay_triangulation_3_from_soup_fmap PUBLIC CGAL::CGAL_Basic_viewer)
   target_link_libraries(remesh_constrained_Delaunay_triangulation_3 PUBLIC CGAL::CGAL_Basic_viewer)
 else()
-  message(STATUS "NOTICE: The example 'conforming_constrained_Delaunay_triangulation_3' requires Qt6, and will not be compiled.")
+  message(STATUS "NOTICE: The example 'conforming_constrained_Delaunay_triangulation_3' cannot draw the result without Qt6.")
 endif()
diff --git a/Constrained_triangulation_3/examples/Constrained_triangulation_3/conforming_constrained_Delaunay_triangulation_3_from_soup_fmap.cpp b/Constrained_triangulation_3/examples/Constrained_triangulation_3/conforming_constrained_Delaunay_triangulation_3_from_soup_fmap.cpp
new file mode 100644
index 00000000000..a09c2a90fc9
--- /dev/null
+++ b/Constrained_triangulation_3/examples/Constrained_triangulation_3/conforming_constrained_Delaunay_triangulation_3_from_soup_fmap.cpp
@@ -0,0 +1,63 @@
+#include <CGAL/draw_triangulation_3.h>
+#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
+#include <CGAL/make_conforming_constrained_Delaunay_triangulation_3.h>
+#include <CGAL/Polygon_mesh_processing/connected_components.h>
+#include <CGAL/Polygon_mesh_processing/polygon_mesh_to_polygon_soup.h>
+#include <CGAL/Surface_mesh/Surface_mesh.h>
+
+#include <algorithm>
+#include <vector>
+
+using K = CGAL::Exact_predicates_inexact_constructions_kernel;
+using Point = K::Point_3;
+using Surface_mesh = CGAL::Surface_mesh<Point>;
+using face_descriptor = Surface_mesh::Face_index;
+
+namespace PMP = CGAL::Polygon_mesh_processing;
+
+int main(int argc, char* argv[])
+{
+  CGAL::Surface_mesh<K::Point_3> mesh;
+  std::vector<K::Point_3> points;
+  std::vector<std::vector<std::size_t>> polygons;
+
+  auto filename = (argc > 1) ? argv[1] : CGAL::data_file_path("meshes/cubes_one_patch_id_per_cc.off");
+  std::ifstream in(filename);
+  if(!in || !(in >> mesh)) {
+    std::cerr << "Error: cannot read file " << filename << std::endl;
+    return EXIT_FAILURE;
+  }
+
+  auto fpmap = mesh.add_property_map<face_descriptor, std::size_t>("f:cc_id").first;
+
+  std::cout << "Read " << mesh.number_of_vertices() << " vertices and "
+            << mesh.number_of_faces() << " polygons" << std::endl;
+
+  PMP::connected_components(mesh, fpmap);
+
+  std::cout << "Number of connected components: "
+            << fpmap[*std::max_element(mesh.faces_begin(), mesh.faces_end(),
+                                [&](face_descriptor f1, face_descriptor f2) {
+                                  return fpmap[f1] < fpmap[f2];
+                                })] + 1
+            << std::endl;
+  PMP::polygon_mesh_to_polygon_soup(mesh, points, polygons);
+
+  auto polygon_to_patch_id = [&](std::size_t i) {
+    return fpmap[*std::next(mesh.faces_begin(), i)];
+  };
+
+  auto soup_fpmap = boost::make_function_property_map<std::size_t>(polygon_to_patch_id);
+
+  auto ccdt = CGAL::make_conforming_constrained_Delaunay_triangulation_3(
+      points, polygons, CGAL::parameters::face_patch_map(soup_fpmap));
+
+  std::cout << "Number of vertices in the CDT: "
+            << ccdt.triangulation().number_of_vertices() << '\n'
+            << "Number of constrained facets in the CDT: "
+            << ccdt.number_of_constrained_facets() << '\n';
+
+  CGAL::draw(ccdt.triangulation());
+
+  return EXIT_SUCCESS;
+}