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RE: Pan Wrap

From: David Dailey <ddailey@zoominternet.net>
Date: Mon, 16 Jul 2012 15:21:59 -0400
To: "'Jasper van de Gronde'" <th.v.d.gronde@hccnet.nl>, <www-svg@w3.org>
Message-ID: <001401cd6388$4551e730$cff5b590$@net>
Agreed on the usefulness of seamless wrapping, reflecting etc. Perhaps for
the time dimension as well, since one often wants an animation to wrap or
reflect seamlessly on either side. To handle the seamlessness, as with
feTile, I've sometimes created a small morphing transition from scene n to
scene 1 to give the illusion of seamlessness; with space, I've used the
feTile strategy of trying to stitch the ends together: 

See these very old DHTML examples of both at 

Time reflection:
http://srufaculty.sru.edu/david.dailey/pictures/dance2/dance.html 
Time wrap (with morph):
http://srufaculty.sru.edu/david.dailey/pictures/etudes/cat/cats.html 
space wrap (with smart edge fuzz):
http://srufaculty.sru.edu/david.dailey/javascript/slip.html 

Jasper and I had a related discussion under "toroidal wraps" a couple of
months ago, as I recall. Non-periodic (as opposed to aperiodic) tilings
might be nice as well using various quasi-random tilings of knot groups, to
allow for interesting applications of Euler diagrams and the like to things
like data-visualization -- some relevant musings on the topic may be seen at
http://srufaculty.sru.edu/david.dailey/weaving.htm .

Animations that wrap time into space and back (with Mobius-like twists in
the middle) could be not only fun, but useful for understanding complex
datasets (like proximities of discrete structures).


Cheers
David


-----Original Message-----
From: Jasper van de Gronde [mailto:jjvdgronde@gmail.com] On Behalf Of Jasper
van de Gronde
Sent: Monday, July 16, 2012 11:30 AM
To: www-svg@w3.org
Subject: Re: Pan Wrap

On 16-07-12 16:56, Doug Schepers wrote:
> Hi, folks-
>
> I was just reminded of a use case I thought of long ago, but never
> articulated: the ability to wrap an SVG image on either (or both) the 
> x or y axis.

This is effectively an example of wanting to construct a pattern with one of
the wallpaper symmetry groups. These are extremely well researched, so when
considering extending SVG with this kind of concept it could be very helpful
to take a closer look at these:

http://en.wikipedia.org/wiki/Wallpaper_group#The_seventeen_groups

In particular, what you're suggesting is effectively group p1 (with some
constraints on the possible translations), and with a little effort you
could easily imagine adding support for at least some of the more closely
related groups, like p2, pm, pg, pmm, pmg and pgg. All of these groups have
real-world examples, although perhaps more for creating patterns than tiling
the viewbox (although in a sense the whole SVG image is then treated as a
pattern).

To continue your map use case, instead of just allowing horizontal wrapping,
it might make sense to also allow vertical wrapping (for certain projections
this makes perfect sense, look for the Peirce quincuncial projection for
example). Now a simple "wrapping" isn't enough, you need something more,
like p2 (which contains 180 degree rotations), or pm (which contains
reflections).
Received on Monday, 16 July 2012 19:22:31 GMT

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