I have vertices and an edge list that describe a planar geometric shape (faces are triangles). For example:
a_______b
/|\ /
/ | \ /
e/__|__\/c
d
Verts: a, b, c, d, e
Edges: (a,b), (a,c), (a,d), (a,e), (b,c), (c,d), (d,e)
So that is all the information I would have about that particular planar geometric shape. In this example, the only internal edges are (a,c) and (a,d). All other edges are border edges. How can I identify those border edges algorithmically (or conversely identify all internal edges)?
Motivation: If it helps, I'm trying to build a navigation mesh, one of the steps of which is to build a visibility graph, the first step of which I think is to identify the border edges.