Implement a ray-casting function approach

[bjlange]

A la this: http://ncase.me/sight-and-light/

We could build polygons by doing this:

1. pick a point
2. do the raycasty funtimes
3. pick a new point inside the raycast polygon (perhaps with a min/max side size)
4. goto 2 (unless the first point chosen is reachable?)

Not sure how to do step 3 other than brute force.

Another idea: rather than sample after the fact, make a nicely spaced set of random points using Best-Candidate or Bridson's algorithm ahead of time. Then step 3 is just filtering all candidate points to ones inside the polygon/radius and picking from there.