title: How to detect border vertices of an open mesh 3d model?
body: <p>There are two kinds of surface mesh models, closed mesh like a sphere or a cube and the second one is the open mesh model which means the surface of the model is not in a closed loop. It is open from somewhere like a hollow pipe.
  Sp what I want is I want to detect the border vertices of the open mesh model. there is no border in closed loop mesh but in open mesh we have to detect border vertices for some smoothing, subdivision, etc. operations. 
  Kindly, suggest me how can I select/detect border vertices ?  what is the optimal way to do this ? 
  by comparing edges of the triangles ? Give me some idea ?</p>
  
  <p>Thanks.</p>