What is a border vertex?

[stla]

That's surely explained in the doc but I didn't find. CGAL finds one border vertex in the curved cylinder at left of the figure below. I thought a border vertex is a vertex on a border edge but there's no border edge here, unless there's an issue in this mesh.

[MaelRL]

Are you sure there is no border edge or is it visually that it does not look like there is a border edge? Can you please provide the mesh & code?

[stla]

Here are the code and the mesh.

    std::set<Mesh3::Vertex_index> constrained_vertices;
    for(Mesh3::Vertex_index v : smesh.vertices()) {
      if(smesh.is_border(v)) {
        constrained_vertices.insert(v);
      }
    }
    {
      const size_t nbv = constrained_vertices.size();
      std::string tail;
      if(nbv > 1) {
        tail = std::to_string(nbv) + " border vertices.\n";
      } else {
        tail = " one border vertex.\n";
      }
      Message("Constraining: " + tail);
    }

Then "one border vertex" is printed.

curvedCylinder.off.txt

[stla]

Ahah stupid! Just seen the mistake, sorry!