s2geometry

Or this https://github.com/google/s2geometry

Howdy, I work on S2 [1] so I have questions! How do you deal with polygons that cross the antimeridian? The indexing structure you've come up with seems very interesting. In spherical coordinates line sweep algorithms like that are a little less intuitive because there's not really a min and max y value to work with. Does your index support multiple polygons indexed together? The lack of exact predicates worries me a little bit. It's tricky because it will work right until it doesn't for mysterious reasons, and it's very hard to test for if you haven't built it on a foundation of exact predicates. You'll periodically fall into the fractal foam around edges when testing if you cross them or not ([2] has some good pictures). We do this in S2 by relying on a set of predicates [3] that fall all the way back to symbolic perturbation if t

I've been looking for good examples for my next book, but everything I've read about has turned out to be not used, including everything in Michael Bader's book [1], except for S2Geometry [2], but I feel like I need to talk to someone who has more expertise in the benefits/drawbacks of using that in an actual product. [1]: https://www.google.com/books/edition/Space_Filling_Curves/zm... [2]: https://github.com/google/s2geometry

> It was quite hard for me to find open-source implementations of linear quadtrees. You probably know this, but the S2 library has one: https://github.com/google/s2geometry

For an example of safe geometric calculation in floating point, see Google's S2 library: https://github.com/google/s2geometry

A geometry library https://s2geometry.io/ (https://github.com/google/s2geometry)

> store and index it by tiles Options include the https://sqlite.org/rtree.html module, and building an application-specific mapping from geometric indexes to an integer keyspace (https://github.com/google/s2geometry or similar). We're using SQLite archives of many GB successfully without issue. As long as the primary keyspace is well-designed (see also https://sqlite.org/withoutrowid.html), ranged queries are extremely fast. > I'm never sure how to properly copy raw struct binary data from sql, directly in ram. BLOB columns and an application-specific serialization/deserialization step work well. memcpy to a struct works if you are absolutely certain that you know what the layout will be. All of the standard perils apply - alignment, internal padding, platform-specific layout, endianness, etc. We're using Protobuf with success. I ima

The Github link was a bit hidden on the page, here it is: https://github.com/google/s2geometry/

"Complicated S2?" That's surprising, the S2 library (https://github.com/google/s2geometry) seems really clean and fairly intuitive to me.