How to detect "bad" (self-intersecting) polygon in code?

Temponautics

Hi, I wonder whether there is a way in code to detect whether a polygon (stored as PoolVector2Array) self-intersects. The Geometry singleton does not seem to have a function for this. I tried:

    func isSelfIntersecting(polygon: PoolVector2Array) -> bool:
    	#returns true if the polygon intersects itself.This does NOT WORK.
    	var ints = Geometry.intersect_polyline_with_polygon_2d(polygon, polygon).size()
    	return ints > 0

Am I doing something wrong, or is there a method somewhere I missed?

TwistedTwigleg

I do not think there is any built-in method for doing this, but it should be computable using an algorithm, like described in this Stackoverflow post.

Temponautics

Thanks @TwistedTwigleg - I had seen that post, and was wondering whether there already is an algorithm implemented in Godot. There does not seem to be. It would probably be simplest to add this where it makes sense (ie Polygon2D or Geometry), and use the Shamos-Hoey Algorithm as described here: https://www.webcitation.org/6ahkPQIsN or here

A complete effective algorithm in C++ can be found here: http://geomalgorithms.com/a09-_avl_code.html

I'll post a request on github.

Temponautics

Added a proposal here: https://github.com/godotengine/godot-proposals/issues/1389