Old school D3 from simpler times
K-D Tree Nearest Neighbor
k-d tree nearest neighbor search
(1-NN). The red dot is the nearest neighbor.
Orange dots are scanned and not selected.
Compare to nearest neighbor search using quadtrees from
this block. The k-d tree technique
seems to scan more points, although the process of limiting the search set is
different so this isn't really a direct measure of which is more efficient.
a more up-to-date version of this block that works for k nearest neighbors.