In fast k-nearest-neighbor search, do you use approximate methods?

[nimajam41]

Hello!
The term "fast" made me confused a little. Does it mean that the nearest neighbors are searched using approximate methods? It will be nice if you can provide some information about this function.

[dancergraham]

Hello. the documentation says that the KNN search is 'based on' nanoflann, which says that it does not use approximate methods but is fast because it uses KD trees https://github.com/jlblancoc/nanoflann

[fwilliams]

@dancergraham is correct. Point-Cloud-Utils uses nanoflann under the hood which does not implement approximate knn. Nanoflann's implementation is considered fast relative to other knn implementations. If you are looking for a library which implements approximate knn methods, then FAISS is a pretty good (though it can be a bit of a pain to install).

[nimajam41]

@fwilliams and @dancergraham , thanks for your guidance!