voronoi tiling goes a bit crazy when points are duplicated in the input

[blackmad]

update: 100% sure this is due to repeated or near-repeated points in the input. Not sure if this is a bug or something you want to fix or try to help clients of the library not shoot themselves in the foot doing. Happy to close this as a user_error_wont_fix.

tl;dr: I noticed today that having repeated points (or near-repeated points because floating point numbers) causes d3-delaunay to return very strange tilings.

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I built a tool that makes extensive use of d3-delaunay, and today when messing around with it I ended up in this surprising state:

(if you follow the blue, it's the raw output of d3-delaunay, you can see that those middle circles are pulling up in a weird way). My code uses cellPolygons and iterates over the points of each polygon.

I put the parameters I was using into an observable notebook and got a slightly different, but still broken tiling:
https://observablehq.com/@blackmad/voronoi-neighbors

(blue are seed points) - notice how those round-ish tiles in the center don't meet?

I don't know how to debug this further. Is this a bug in d3-delaunay?

[mourner]

This is a numerical robustness issue — Delaunator (the underlying library) fails on certain cases with convoluted floating point data. If I round the coordinates (in this case to 2 decimal points), it works properly:

Closing in favor of mapbox/delaunator#61 — there is a workaround for the library but it would increase the dependency size quite a bit, so I'm thinking of producing multiple builds (robust and lite non-robust).