From dd653cd3960c2db50239aea70c33466f2e006b35 Mon Sep 17 00:00:00 2001
From: Guillaume Damiand <guillaume.damiand@liris.cnrs.fr>
Date: Mon, 7 Mar 2022 17:32:26 +0100
Subject: [PATCH 1/3] Update nef_3 draw to deal with faces with holes.

---
 Nef_3/include/CGAL/draw_nef_3.h | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/Nef_3/include/CGAL/draw_nef_3.h b/Nef_3/include/CGAL/draw_nef_3.h
index 2931c43f407..14f8332262a 100644
--- a/Nef_3/include/CGAL/draw_nef_3.h
+++ b/Nef_3/include/CGAL/draw_nef_3.h
@@ -103,9 +103,10 @@ protected:
         return;
       }
 
+
+      
       SHalfedge_const_handle se;
-      Halffacet_cycle_const_iterator fc;
-      fc = f->facet_cycles_begin();
+      Halffacet_cycle_const_iterator fc=f->facet_cycles_begin();
 
       se = SHalfedge_const_handle(fc); // non-zero if shalfedge is returned
       if(se == 0)
@@ -118,13 +119,35 @@ protected:
 
       SHalfedge_around_facet_const_circulator hc_start(se);
       SHalfedge_around_facet_const_circulator hc_end(hc_start);
+      Vertex_const_handle lastvh;
       CGAL_For_all(hc_start, hc_end) {
-        Vertex_const_handle vh = hc_start->source()->center_vertex();
+        Vertex_const_handle vh=hc_start->source()->center_vertex();
+        lastvh=vh;
         viewer.add_point_in_face(vh->point(),
                                  viewer.get_vertex_normal(vh));
       }
+
+      // Now iterate through holes of the face
+      ++fc;
+      while(fc!=f->facet_cycles_end())
+      {
+        se = SHalfedge_const_handle(fc);
+        hc_start=se;
+        hc_end=hc_start;
+        CGAL_For_all(hc_start, hc_end) {
+          Vertex_const_handle vh=hc_start->source()->center_vertex();
+          viewer.add_point_in_face(vh->point(),
+                                   viewer.get_vertex_normal(vh));
+        }
+        viewer.add_point_in_face(hc_start->source()->center_vertex()->point(),
+                                 viewer.get_vertex_normal(hc_start->source()->center_vertex()));
+        viewer.add_point_in_face(lastvh->point(),
+                                 viewer.get_vertex_normal(lastvh));
+        ++fc;
+      }
+      
       viewer.face_end();
-      facets_done[f] = true;
+      facets_done[f]=true;
       n_faces++;
     }
 

From 182389ed44328d7f2fe6b183ee0a2a9c4b32e431 Mon Sep 17 00:00:00 2001
From: Guillaume Damiand <guillaume.damiand@liris.cnrs.fr>
Date: Mon, 7 Mar 2022 17:33:07 +0100
Subject: [PATCH 2/3] Update draw nef3 example to observe faces with holes

---
 Data/data/meshes/beam.off           | 16 ++++++++++++++++
 Nef_3/examples/Nef_3/draw_nef_3.cpp | 13 ++++++++-----
 2 files changed, 24 insertions(+), 5 deletions(-)
 create mode 100644 Data/data/meshes/beam.off

diff --git a/Data/data/meshes/beam.off b/Data/data/meshes/beam.off
new file mode 100644
index 00000000000..8d0908dc812
--- /dev/null
+++ b/Data/data/meshes/beam.off
@@ -0,0 +1,16 @@
+OFF
+8 6 0
+2.7 2.7 2.3
+2.7 2.3 2.3
+2.3 2.7 2.3
+2.3 2.3 2.3
+2.7 2.7 -1.3
+2.7 2.3 -1.3
+2.3 2.7 -1.3
+2.3 2.3 -1.3
+4 0 1 3 2 
+4 5 4 6 7 
+4 0 2 6 4 
+4 3 1 5 7 
+4 0 4 5 1 
+4 6 2 3 7 
diff --git a/Nef_3/examples/Nef_3/draw_nef_3.cpp b/Nef_3/examples/Nef_3/draw_nef_3.cpp
index f5923ffe451..0ccd07ba6f9 100644
--- a/Nef_3/examples/Nef_3/draw_nef_3.cpp
+++ b/Nef_3/examples/Nef_3/draw_nef_3.cpp
@@ -13,15 +13,18 @@ typedef CGAL::Nef_polyhedron_3<Kernel>                      Nef_polyhedron;
 int main(int argc, char *argv[])
 {
   // read OFF file into a polyhedron
-  Polyhedron P;
-  std::ifstream ifs((argc > 1) ? argv[1] : CGAL::data_file_path("meshes/cross_quad.off"));
-  ifs >> P;
+  Polyhedron P1, P2;
+  std::ifstream ifs1((argc > 1) ? argv[1] : CGAL::data_file_path("meshes/cross_quad.off"));
+  ifs1 >> P1;
+  std::ifstream ifs2((argc > 1) ? argv[1] : CGAL::data_file_path("meshes/beam.off"));
+  ifs2 >> P2;
 
   // initialize nef from polyhedron
-  Nef_polyhedron N(P);
+  Nef_polyhedron N1(P1);
+  Nef_polyhedron N2(P2);
 
   // draw Nef Polyhedron
-  CGAL::draw(N);
+  CGAL::draw(N1-N2);
 
   return EXIT_SUCCESS;
 }

From 2df2398108427a7b101f6d9f57ee482100413064 Mon Sep 17 00:00:00 2001
From: Guillaume Damiand <guillaume.damiand@liris.cnrs.fr>
Date: Mon, 7 Mar 2022 17:37:54 +0100
Subject: [PATCH 3/3] trailing...

---
 Nef_3/include/CGAL/draw_nef_3.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Nef_3/include/CGAL/draw_nef_3.h b/Nef_3/include/CGAL/draw_nef_3.h
index 14f8332262a..e654ea9aae7 100644
--- a/Nef_3/include/CGAL/draw_nef_3.h
+++ b/Nef_3/include/CGAL/draw_nef_3.h
@@ -104,7 +104,7 @@ protected:
       }
 
 
-      
+
       SHalfedge_const_handle se;
       Halffacet_cycle_const_iterator fc=f->facet_cycles_begin();
 
@@ -145,7 +145,7 @@ protected:
                                  viewer.get_vertex_normal(lastvh));
         ++fc;
       }
-      
+
       viewer.face_end();
       facets_done[f]=true;
       n_faces++;