How should pgr_planarFaces handle the outer face during traversal?

pgRouting pgrouting-users
1

While studying planar face traversal and experimenting with small Graphviz examples, I used the following planar graph:

graph {
    layout=neato;

    1 -- 2;
    2 -- 3;
    3 -- 4;
    4 -- 1;
}

graphviz
graphviz156×134 1.87 KB

My understanding is that this graph should contain:

  • one bounded inner face {1,2,3,4}
  • one unbounded outer face

From reading the Boost documentation for planar_face_traversal:

it seems that boost::planar_face_traversal also traverses the unbounded outer face during traversal.

For pgr_planarFaces, would it make more sense to:

  • return the outer face by default, or
  • expose it through an optional parameter like include_outer_face => true?