Fixed PolyConnectivity is_collapse_ok, missing some configurations (Thanks to...

Fixed PolyConnectivity is_collapse_ok, missing some configurations (Thanks to Simon Flöry for the patch)

src/OpenMesh/Core/Mesh/PolyConnectivity.cc

@@ -364,14 +364,16 @@ bool PolyConnectivity::is_collapse_ok(HalfedgeHandle v0v1)
 
   //the edges v1-vl and vl-v0 must not be both boundary edges
   //this test makes only sense in a polymesh if the side face is a triangle
+  VertexHandle vl;
   if (!is_boundary(v0v1))
   {
     if (v0v1_triangle)
     {
-      //VertexHandle vl = to_vertex_handle(next_halfedge_handle(v0v1));
-
       HalfedgeHandle h1 = next_halfedge_handle(v0v1);
       HalfedgeHandle h2 = next_halfedge_handle(h1);
+      
+      vl = to_vertex_handle(h1);
+      
       if (is_boundary(opposite_halfedge_handle(h1)) && is_boundary(opposite_halfedge_handle(h2)))
         return false;
     }
@@ -379,19 +381,24 @@ bool PolyConnectivity::is_collapse_ok(HalfedgeHandle v0v1)
 
   //the edges v0-vr and vr-v1 must not be both boundary edges
   //this test makes only sense in a polymesh if the side face is a triangle
+  VertexHandle vr;
   if (!is_boundary(v1v0))
   {
     if (v1v0_triangle)
     {
-      //VertexHandle vr = to_vertex_handle(next_halfedge_handle(v1v0));
-
       HalfedgeHandle h1 = next_halfedge_handle(v1v0);
       HalfedgeHandle h2 = next_halfedge_handle(h1);
+      
+      vr = to_vertex_handle(h1);
+      
       if (is_boundary(opposite_halfedge_handle(h1)) && is_boundary(opposite_halfedge_handle(h2)))
         return false;
     }
   }
 
+  // if vl and vr are equal and valid (e.g. triangle case) -> fail
+  if ( vl.is_valid() && (vl == vr)) return false;
+
   // edge between two boundary vertices should be a boundary edge
   if ( is_boundary(v0) && is_boundary(v1) && !is_boundary(v0v1) && !is_boundary(v1v0))
     return false;

src/Unittests/unittests_trimesh_collapse.cc

@@ -741,5 +741,4 @@ TEST_F(OpenMeshCollapse, DeletedStatus) {
   EXPECT_FALSE(mesh_.status(mesh_.opposite_halfedge_handle(bottom_right)).deleted()) << "Halfedge from vertex 5 to vertex 3 is deleted";
 }
 
-
 }