The original description follows; it's greater in scope than the new title:
This is a proposal for the "spatial3d" module to be purely about the shape/geometry implementations it has. In Lucene 5 that's actually all it has. In Lucene 6 at the moment its ~76 files have 2 classes that I think should go elsewhere: Geo3DPoint and PointInGeo3DShapeQuery. Specifically lucene-spatial-extras (which doesn't quite exist yet so lucene-spatial) would be a suitable place due to the dependency. Eventually I see this module migrating elsewhere be it on its own or a part of something else more spatial-ish. Even if that never comes to pass, non-Lucene users who want to use this module for it's geometry annoyingly have to exclude the Lucene dependencies that are there because this module also contains these two classes.
In a comment I'll suggest some specifics.