Unstable union result

The expected result is this

but every now and then artifacts appear like this

The artifacts seem to depend on the order of the unified polygons. Spade's r-tree is used to union polygons in parallel.

For some reason applying union on these polygons sequentially:

causes this result:

Gathering more data, the union of red with blue causes these results:

[untoldwind]

Have you checked with the javascript version (https://github.com/w8r/martinez)?

I.e. to figure out if it is a problem with the algorithm itself or the rust-port.

[bluenote10]

@michaort Very interesting test cases. It has been a while, but do you happen to still have the raw data of these polygons? I'd be curious if we can make them work now.

Sorry I've just spotted this in my emails. I looked through my backups but couldn't find any dumps of the raw data. Though you could probably generate similar data. If you generate a maze made out of square polygons, increase their size to overlap each other, and then union them sequentially, you should get similar problems. One might have to sprinkle in randomly placed rectangles of various sizes and rotations if that doesn't do the trick.