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The Hat and the Spectre (momath.org)
11 points by Tomte 10 months ago | hide | past | favorite | 9 comments



This is just the beginning I hope. Next is 3D. Or shapes that are dynamic in time like lava lamps and the digits of pi.

Has anyone here read Neal Steve's Anathem?

It's a utopian book that I think a lot of idealists can relate to. Math being a sacred institution, a kind of royal society. It's a great explanation of these kinds of patterns but in the most hardcore way.


A note on these shapes for people who want to draw them from scratch...

I found it quite difficult to draw a nice looking tiling using the basic monotile. It's quite hard to draw it entirely from the angles directly on the paper - not for a single tile, but extending any patch to a much larger one.

Tracing and transferring the tile, on the other hand is easier to keep track of, but slight inaccuracies quickly propagate across the diagram. Since there is (by definition!) no larger-scale structure, there can be no guidelines to help correct this - unlike for repeated patterns.

The way I found was best was just to print out a patch of tiles, and then trace that. I suppose that using a metatile approach might also work, although doing that by hand is a little daunting.


I came up with some L systems for drawing hats and spectres based on the metatiles eg

https://trinket.io/python/274cc18bd5

https://trinket.io/python/108e28ab75

(the second program has a bunch of variant versions)

this cheats a little: it turns out you always want to draw the H8 metatile (which will overlap) instead of keeping track of the zoo of metatiles. And the flipped hat is never drawn; it appears as a hole in the plot. Similar things happen with the spectre.

This was all done so I could make a program small enough to fit in a toot to generate patches using the bbc microbot:

https://mastodon.me.uk/@bbcmicrobot/110295593252210445

(also for hand drawing hats, use a hexagonal grid under your tracing paper, since it's just an assembly of kites)


Very nice! Have you seen Simon Tatham’s articles on Penrose tiles, Hats, and Spectres? https://www.chiark.greenend.org.uk/~sgtatham/quasiblog/aperi... https://www.chiark.greenend.org.uk/~sgtatham/quasiblog/aperi...


Thanks, I'll try the L-system. I did try drawing on triangulated grid paper (dual to hex grid), which helped a little.


The Hat lives on a hexagonal grid which ought to help you correct inaccuracies.


Well the metatiles are hexagonal - does that literally mean using an underlying hex grid would work? I'll certainly try that, thanks!


You can see the underlying grid in this image https://cs.uwaterloo.ca/~csk/hat/examples/hats.png from this page https://cs.uwaterloo.ca/~csk/hat/


Would be nice to have these shapes as actual tiles. For paving ones' terrace, or a square in city center etc.




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