Does multipoint,multiPolyline,multiPolygon support？

[LemonLiTree]

I did not find support for multipoint, multiPolyline, multiPolygon, does the community have any considerations?

[jmr]

An S2Polygon is essentially a MultiPolygon. For the others, you can maybe use S2RegionUnion, depending on what you're trying to do. What is the problem you're trying to solve?

[LemonLiTree]

Can I understand that when there is only one loop in Polygon, it is Polygon, and when there are multiple loops, it is multiPolygon？

[jmr]

Loops can be nested with the opposite orientation to create holes. I think geojson plain polygons can do this. I'm not really sure what "MultiPolygon" you're asking about.

If loops don't contain each other, then it's the union of separate polygons. See s2polygon.h and s2loop.h.

[LemonLiTree]

MultiPolygon in GEOS

[smcallis]

S2Shape can be all of those because it can contain multiple chains of a particular dimension, that gives you multipoint and multipolyline, and then S2Shape can represent both simple and complex (disjoint interior area) polygons. Whether you consider a 2D S2hape to be one polygon or a group of multiple polygons is a matter of interpretation.

[eengle]

A Polygon has one shell, or outermost ring. A MultiPolygon has multiple shells. But on the sphere, there isn't really a good sense of "outermost". Consider a polygon formed by a ring at 10 degrees north and a ring at 10 degrees south, oriented so that the polygon contains the 20 degree tall band of latitude centered on the equator. Unlike 2D geometry where you need to know which ring is the outermost, it doesn't matter on the sphere -- the +10 ring can be the shell with a hole at -10 latitude, or vice-versa. Similarly, S2 operations aren't specialized on the dimension of the geometries, so there are no specific types for MultiLine and MultiPoint. But you can create collections, either as a simple vector of S2Shape*, or as an S2ShapeIndex if you want to operate on the collection as a whole. This indexed collection type is another great strength of S2 over libraries like GEOS, which only provide much simpler indexes of envelopes. This makes a large difference in performance when you have to work with complex lines or polygons, especially. Kind regards, Eric

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On Thu, Apr 27, 2023 at 7:33 AM smcallis ***@***.***> wrote: S2Shape can be all of those because it can contain multiple chains of a particular dimension, that gives you multipoint and multipolyline, and then S2Shape can represent both simple and complex (disjoint interior area) polygons. Whether you consider a 2D S2hape to be one polygon or a group of multiple polygons is a matter of interpretation. — Reply to this email directly, view it on GitHub <#314 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AA4DAANW4G3MFHTLAY43BNDXDJ7T7ANCNFSM6AAAAAAXNOQHLA> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>