Just so that other people don't have to search: http://lpetrich.org/Science/GeometryDemo/GeometryDemo_GMap.h...

and a very good tutorial: https://chriszetter.com/blog/2014/06/15/building-a-voronoi-m...

on how the UK supermarkets Voronoi map was made: https://chriszetter.com/voronoi-map/examples/uk-supermarkets...

also have a look at (code included): http://bl.ocks.org/shimizu/5610671