From ed0c55df89c92364f30a4b53b2e9a95c782eb5a4 Mon Sep 17 00:00:00 2001
From: Guillaume Damiand <guillaume.damiand@liris.cnrs.fr>
Date: Thu, 5 Apr 2018 10:16:43 +0200
Subject: [PATCH] Bugfix in function that test if a face is convex.

---
 GraphicsView/include/CGAL/Buffer_for_vao.h | 24 +++++++++-------------
 1 file changed, 10 insertions(+), 14 deletions(-)

diff --git a/GraphicsView/include/CGAL/Buffer_for_vao.h b/GraphicsView/include/CGAL/Buffer_for_vao.h
index c7fe936dd90..607be5d58a8 100644
--- a/GraphicsView/include/CGAL/Buffer_for_vao.h
+++ b/GraphicsView/include/CGAL/Buffer_for_vao.h
@@ -372,15 +372,13 @@ public:
 
     if (m_points_of_face.size()==3)
     { triangular_face_end_internal(normal); } // Triangle: no need to triangulate
-    /*
-      // TODO BUG FIX HERE
-      else if (is_current_face_convex(normal))
+    else if (is_current_face_convex(normal))
     {
       if (m_points_of_face.size()==4)
       { convex_quadrangular_face_end_internal(normal); } // Convex quad
       else 
       { convex_face_end_internal(normal); } // Convex face with > 4 vertices
-      } */
+    }
     else
     { // Non convex and more than 3 points: we triangulate
       nonconvex_face_end_internal(normal);
@@ -421,15 +419,15 @@ public:
   static bool is_facet_convex(const std::vector<Local_point>& facet,
                               const Local_vector& normal)
   {
-    Local_kernel::Orientation orientation;
+    Local_kernel::Orientation orientation, local_orientation;
     std::size_t id=0;
     do
     {
       const Local_point& S=facet[id];
-      const Local_point& T=facet[id+1];
+      const Local_point& T=facet[(id+1==facet.size())?0:id+1];
       Local_vector V1=Local_vector((T-S).x(), (T-S).y(), (T-S).z());
 
-      const Local_point& U=facet[id+2];
+      const Local_point& U=facet[(id+2==facet.size())?0:id+2];
       Local_vector V2=Local_vector((U-T).x(), (U-T).y(), (U-T).z());
 
       orientation = Local_kernel::Orientation_3()(V1, V2, normal);
@@ -440,24 +438,22 @@ public:
 
     //Here, all orientations were COPLANAR. Not sure this case is possible,
     // but we stop here.
-    if (orientation==CGAL::COPLANAR)
+    if (orientation==CGAL::COPLANAR || orientation==CGAL::ZERO)
     { return false; }
 
     // Now we compute convexness
     for(id=0; id<facet.size(); ++id)
     {
       const Local_point& S=facet[id];
-      const Local_point& T=facet[id+1];
+      const Local_point& T=facet[(id+1==facet.size())?0:id+1];
       Local_vector V1=Local_vector((T-S).x(), (T-S).y(), (T-S).z());
       
-      const Local_point& U=facet[id+2];
+      const Local_point& U=facet[(id+2==facet.size())?0:id+2];
       Local_vector V2=Local_vector((U-T).x(), (U-T).y(), (U-T).z());
       
-      orientation = Local_kernel::Orientation_3()(V1, V2, normal);
+      local_orientation=Local_kernel::Orientation_3()(V1, V2, normal) ;
 
-      Local_kernel::Orientation res=Local_kernel::Orientation_3()(V1, V2, normal) ;
-
-      if(res!=CGAL::ZERO && res!=CGAL::COPLANAR && res!=orientation)
+      if(local_orientation!=CGAL::ZERO && local_orientation!=orientation)
       { return false; }
     }
     return true;