Edge Routing

[stargazing-dino]

[I'll update this as I learn more]

On the (graphviz website)[https://www.graphviz.org/theory/] I found this paper that looks interesting:

Implementing a General-Purpose Edge Router - edge routing in Graphviz

They pointed out two methods to draw edges. Polylines with card edges (or curved based on a border radius) or splines.

Splines

A directed graph they looked at had this algorithm to draw splines:

The method used in dot [6] incorporates a more general heuristic with two
phases. For a given edge to be drawn, the 1st phase computes the \white space"
or constraint polygon where the edge may be drawn so as not to touch any
other nodes or create unwanted edge crossings. The second phase ts a smooth
spline connecting the edge's endpoints and staying within the constraint polygon.
The endpoints can have optional slope constraints. The spline tting heuristic
computes a trial spline between the endpoints. If the spline goes outside the
constraint polygon, and it cannot easily be repaired by slight re-aiming, then
the spline tter subdivides the polygon near the broken constraint and draws
the top and bottom halves recursively.

Polylines

https://cs.brown.edu/people/rtamassi/gdhandbook/chapters/orthogonal.pdf