[trebcon]

The implicit grid data structure from there is a personal favorite of mine. I used it in a game once and it performed incredibly well for our use case.

It's a bit too complicated to totally summarize here, but it uses a bit per object in the scene. Then bit-wise operations are used to perform quick set operations on objects.

This data structure got me generally interested in algorithms that use bits for set operations. I found the Roaring Bitmap github page has a lot of useful information and references wrt this topic: https://github.com/RoaringBitmap/RoaringBitmap

[phkahler]

I spent a lot of time optimizing an octree for ray tracing. It is my favorite "spatial index" because it's the only one I know that can be dynamically updated and always results in the same structure for given object placement.