Algorithms implemented in `graph.py`

[arbenede]

I am debugging a problem with the union of several non convex spherical polygons related the wrong calculation of the inside point of the union SP. Are the algorithms implemented in graph.py from some paper or textbook?

[mcara]

@mdboom might know.

[nden]

I think the history is a bit lost. It was based on closed source software, developed at an astronomy department, which was shared with us. Can you provide a simple example that illustrates the problem?