Handedness issues

[keijokapp]

The README says that the output exterior paths are supposed to be CCW and holes CW. But that doesn't seem to be the case.

Here's an example:

Intersecter#calculate outputs the segments ordered by their end events. That would be [AB, AC, BC] in this case. SegmentChainer then looks at myFill.above of the first segment (AB) and determines that the polygon is not filled so it erroneously outputs it clockwise. Note that if B were to the right of C then the first segment would be AC and SegmentChainer would treat the polygon as filled.

I'm trying to understand the intentions here: is Intersecter#calculate supposed to output the segments in a different order so that AC would be processed first?; or is SegmentChainer supposed to look at the direction of segments and use the correct fill flag?

[velipso]

I haven't looked at the code in a while, but looks like this part is responsible for getting the winding correct:

https://github.com/velipso/polybool/blob/main/src/SegmentChainer.ts#L265

[keijokapp]

Thanks for the quick response.

Yes, but it uses the wrong fill flag. It takes the "above" fill flag of the first segment it encounters (AB which would be false). The question is, is it the problem with SegmentChainer (not taking the rest of the chain into account) or Intersecter#calculate (outputting segments in wrong order)?

Seems like if the segments were ordered by their start events (and CCW if start events are the same) then using the first segment fill flag would be appropriate.
EDIT: That doesn't really work. I think I've found a real solution and I'm preparing a PR.