Hi David Smiley,
I have been working on a prefix tree based on goggle S2 geometry (https://s2geometry.io/) to be used mainly with Geo3d shapes with very promising results, in particular for complex shapes (e.g polygons). Using this pixelization scheme reduces the size of the index, improves the performance of the queries and reduces the loading time for non-point shapes.
If you are ok with this contribution and before providing any code I would like to understand what is the correct/prefered approach:
1) Add new depency to the S2 library (https://mvnrepository.com/artifact/io.sgr/s2-geometry-library-java). It has Apache 2.0 license so it should be ok.
2) Create a utility class with all methods necessary to navigate the S2 tree and create shapes from S2 cells (basically port what we need from the library into Lucene).
What do you think?