Somewhere, I don't remember where, I saw a beautiful 3D figure of part a CAT(0) simplicial complex. I am thinking and hoping that this was some finite piece of an affine building of type A2, presumably in characteristic 2. But I'm very frustrated now that I just can't remember exactly what I saw or where I saw it. It was something like part of the neighborhood of radius 1 or radius 2 of a vertex, with enough simplices removed so that the rest fits in $\mathbb{R}^3$. It looked like Mathematica graphics, since (in my recollection) it had good colors to help show the 3-dimensional structure. I'm thinking that I saw it in the AMS Notices, but it could also have been in an AMS calendar or elsewhere. Does anyone remember seeing an image like this, and if so, where?


I'm asking because I'd like to have such an image in a paper that I'm working on, not necessarily the one that I saw but something similar.




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I got some good answers to my question, both here and in private e-mail to Bill Casselman. But in the end I decided to make my own diagram (with the aid of TikZ and ~~Python~~ SAGE). Here it is.


[alt text http://www.freeimagehosting.net/uploads/e38638d43e.png](http://www.freeimagehosting.net/uploads/e38638d43e.png)




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For those who are interested in the TikZ and SAGE code, I combined them into one TeX document. I posted both [the TeX source](http://www.math.ucdavis.edu/~greg/a2building.tex) and [its PDF output](http://www.math.ucdavis.edu/~greg/a2building.pdf) (from pdflatex) on my web page.



Looking for figure of part of an A2 affine building
Check out <http://dean.clas.uconn.edu/teitelbaum/colorout.gif>


I made this image long ago for the cover of the AMS Notices.


See <http://www.ams.org/notices/199510/teitelbaum.pdf>


