[cairo] Spirolaterals

[Bryce Harrington]

On Wed, Oct 05, 2016 at 07:35:16PM +1300, Lawrence D'Oliveiro wrote:
> I’ve been enhancing my curve script
> <https://lists.cairographics.org/archives/cairo/2016-May/027422.html>
> to draw spirolaterals
> <http://www.mi.sanu.ac.rs/vismath/krawczyk/spdesc00.htm>. Has anyone
> else looked at these?

No, but I have seen a lot of folks in Inkscape working on a lot of
similar kinds of things.  The description of spirolaterals reminded me a
lot of Inkscape's Tiled Clones functionality, which are basically
rule-based methods of replicating a base shape with different rotations,
transformations, etc.  However, I wasn't able to replicate a
spirolateral with tile clones (admittedly maybe more due to my limited
skills than limitation of the software).

Most likely if anyone's done anything with spirolaterals for Inkscape
it'd be as an extension, which are basically command line scripts that
take an SVG snippet and morph it according to parameters specified as
command line arguments.  In poking around the closest I found was the
Spirograph extension; have you played with that at all?  The code for
the extension is at /usr/share/inkscape/extensions/spirograph.py if it
looks at all interesting.

> All the examples I have tried work fine--except for those with
> reversing turns. My conclusion is that many of the examples shown here
> <http://www.mi.sanu.ac.rs/vismath/krawczyk/spdesc03.htm> are mixed up
> or just plain mislabelled. For example, in figure 6, the one labelled
> (substituting slashes for subscripts) “9/90/1,2,3,4” should actually be
> “9/90/1,2,3,9”, “9/90/2,3,4” should be “9/90/1,2,9” and “9/90/2,3,4,5”
> should actually be “9/90/1,2,3,4”.
> 
> If there were a bug in my code, then for example I wouldn’t get
> “9/90/1,2,3” correct--the errors would be more systematic.

Bryce