Message #1898

From: Roice Nelson <>
Subject: Re: [MC4D] Re: yet more new puzzles and a prize
Date: Sun, 06 Nov 2011 18:42:58 -0600

No worries at all - I had just wanted to let you know rotation was

It looks like Don has hardcoded the motion model (which he did
independently of the hyperbolic geometry model), and not provided a key
toggle to switch it. My apologies for not mentioning that earlier. To see
the other models, you’d need to recompile his applet after altering the
code. In the version I have downloaded, the code is around line 1374 of
the file HyperbolicApplet.prejava file, and looks like this:

//int motionModel = TRACKBALL;<br>
//int motionModel = DRAG&#95;GEODESIC;<br>
//int motionModel = DRAG&#95;NONPRECESSING;<br>
int motionModel = DRAG&#95;PURETRANSLATE&#95;CLAMPED;

You could change what is commented to try the other models. Getting a
setup to recompile would probably take some effort though.

With regards to hyperbolic geometry models, I’ve played with a few of these
in MagicTile, but I haven’t yet made the controls work for them. I just
uploaded a couple pictures… some puzzles in the Klein model, and one
pasted on the pseudosphere <>.
The Klein model may become my favorite view when solving puzzles. It has
a very spherical feel to it, due to circles getting squashed towards the
edges, and magnifies pieces near the center. I don’t think the
pseudosphere ends up being a very workable view, since you can’t show a
large percentage of the hyperbolic plane on it at once.


On Sat, Nov 5, 2011 at 4:38 PM, schuma <> wrote:

> Sorry for not noticing the middle mouse drag function.
> In Don’s applet I don’t know how to change to another motion model.
> Poincare model/Klein model behave in the same way. I’m not surprised by
> anti-procession because rolling a ball is anti-procession. Since sphere and
> hyperbolic plane are opposite, it’s natural to see procession in the
> hyperbolic plane. But I don’t know how to see anti-procession in hyperbolic.
> Nan
> — In, Roice Nelson <roice3@…> wrote:
> >
> > Middle-mouse drag will do a rotation for you (or on a laptop, left+right
> > drag at the same time).
> >
> > I find the noncommutative panning in spherical/hyperbolic spaces really
> > neat too (doesn’t happen for Euclidean space, so middle-mouse control is
> > required there). The code for Don’s hyperbolic tesselations
> > applet<>was super helpful
> > in understanding and implementing this. Internally, you
> > can see he played with a few different motion models, some of which
> > anti-precess rather than precess! That is, dragging clockwise results
> in a
> > counterclockwise rotation of the space. I found that I liked the one he
> > settled on for his applet the best too, though it’d be nice to add in
> some
> > of the others as an option.
> >
> > seeya,
> > Roice