I've only skimmed the article so their solution seems like a totally valid way to do polygon intersections for their purposes, but for people that want to do th

I've only skimmed the article so their solution seems like a totally valid way to do polygon intersections for their purposes, but for people that want to do this in a more rigorous way, there's something called the Vatti clipping algorithm which does boolean operations on arbitrary 2D polygons (in polynomial time). To find polygon intersections, one can do a boolean "intersect" operation to see if the resulting operation has any results. If so, the polygons intersect. If not, then they're disjoint. Angus Johnson has created ClipperLib [1] which implements Vatti's algorithm and is available in a variety of languages, including C++, with ports to Javascript by others [2]. CGAL [3] can do polygon clipping but, from my own experience, ClipperLib is about 400 times faster. [0] https://en.wikipedia.org/wiki/Vatti_clipping_algorithm https://en.wikipedia.org/wiki/Vatti_clipping_algorithm [1] http://www.angusj.com/clipper2/Docs/Overview.htm http://www.angusj.com/clipper2/Docs/Overview.htm [2] https://github.com/junmer/clipper-lib https://github.com/junmer/clipper-lib [3] https://www.cgal.org/ https://www.cgal.org/