[Edu-sig] turtle coordinates: Y increase downards - as in most graphics API?

[kirby urner]

Hi Sergio --

Thanks for taking a look at the Q-ray coordinates!

You're right about many bridges to crystallography in this neighborhood.

​I'm part of a tiny subculture that came up with Q-rays in a listserv long
ago.

http://mathforum.org/library/view/6236.html

It's not that I'm the only one familiar with the ideas or that I'm the only
contributor, just I know of no one else bringing it to the attention of a
pre-college class, and I do that only rarely.

The connection with Python is a Quadray class is implemented therein.  My
friend Tom has them in C++ (see Wikipedia).

https://github.com/4dsolutions/Python5/blob/master/QuadraysJN.ipynb

I've also dabbled in a Clojure version.

https://github.com/4dsolutions/synmods/blob/master/qrays.clj

I worked with Quaternions a long time ago, to do a rotating cube applet,
but then applets became a deprecated technology, much to everyone's
surprise and consternation.

http://4dsolutions.net/ocn/oopalgebra.html

Kirby
​

On Tue, Jun 19, 2018 at 12:14 PM, Sergio Rojas <sergio_r at mail.com> wrote:


> Kirby,
>
> Looking way far in the back of my head,
> the closest thing (to the inspirational drawings of
> your notebook) I could recover
> is what is called fundamental lattice structures of
> solid state physics. Not sure, but in there
> they might use your coordinate system to better describe
> structures of crystals.
> The book by Kittel, pg 27 of the 8th Edition, has some stuff on it.
>
> Other object in that sense is the Quaternion thing
>   https://en.wikipedia.org/wiki/Quaternion
>
> Better stop here, I am getting hurt ...
>
> Sergio
>
>
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