Request: concave hull support about geoswift

[macdrevx]

Might https://github.com/GEOSwift/GEOSwift/blob/main/Sources/GEOSwift/GEOS/Boundable.swift be what you're looking for?

[alessdiimperio]

Aha ill chwck it out, perhaps misunderstoor the image as it shows just lines and not filled in polygon. If it works itll make my day

[alessdiimperio]

Hmm im not sure i understand the usage of boundary.

What im trying to resolve is when users intersect lines in a polygon. instead of throwing an error, i want to ignore the internal intersection and create a polygon without the internal holes.

the concave hull algorithm is supposed to do just that. How can boundary be used for the same outcome?

Link to concave hull example
https://github.com/SanyM/ConcaveHull

now while there are packages like the above that support concave hull it would be nice to be able to solve the problem with less dependencies if possible.

[macdrevx]

Apologies for my confusion. It looks like concave hull is new in geos 3.11. GEOSwift is currently on 3.10. We'll add concave hull after we update. (hopefully soon!)

[alessdiimperio]

🤞 here's hoping :)
great work with the framework

[macdrevx]

@alessdiimperio @vladislavitsi concave hull is now available on the main branch. Please give it a try and let me know if it looks okay!

[alessdiimperio]

any example of how the implementation works?

to get these changes should i add => mainbranch url in pods?

[macdrevx]

I released the changes in v10: https://github.com/GEOSwift/GEOSwift/releases/tag/10.0.0

I don't have any examples, but the release notes at that link show the method name. You just invoke it on any geometry.

[alessdiimperio]

Tested it finally, and while it works, it unfortunately doesn't give the desired effect in many cases even.
Is there some other way to ignore "holes" in LinearRings ? or ignore the internal coordinates when a linearRing intersects itself?
With the images i provided as some sort of example.

[macdrevx]

@dr-jts could you please advise here?

[dr-jts]

Perhaps the GEOSMakeValid function could help here? Note that this probably needs the GEOS_MAKE_VALID_STRUCTURE method (use GEOSMakeValidWithParams to specify this).

For a full explanation see https://lin-ear-th-inking.blogspot.com/2021/05/fixing-invalid-geometry-with-jts.html

[macdrevx]

Thank you! @alessdiimperio, we expose only GEOSMakeValid (makeValid() on any GeometryConvertible) right now, but we'd be happy to expose GEOSMakeValidWithParams as well. Would you mind opening a new issue to track that?