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Re: Strange size changes in Manipulate with GeometricTransformation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg92210] Re: [mg92156] Strange size changes in Manipulate with GeometricTransformation
  • From: John Fultz <jfultz at wolfram.com>
  • Date: Tue, 23 Sep 2008 07:31:36 -0400 (EDT)
  • Reply-to: jfultz at wolfram.com

This bug had already been discovered by our QA department and logged in our
database.  I've added a pointer to your post to that bug report.  In the mean 
time, the way to work around this is to provide an explicit PlotRange. E.g.,

Manipulate[
Graphics[
GeometricTransformation[
{
EdgeForm[Black],
FaceForm[],
Disk[{0, 0}, 1, {\[Pi], 2 \[Pi]}],
Disk[{0, 0}, 1, {0, \[Pi]}]
}, RotationTransform[x]
], PlotRange->{{-1.1,1.1},{-1.1,1.1}}
], {x, -180, 180}
]

Also note that x is in radians, not degrees, which is why your example rotates 
so very quickly.

Sincerely,
 
John Fultz
jfultz at wolfram.com
User Interface Group
Wolfram Research, Inc.

On Mon, 22 Sep 2008 05:24:39 -0400 (EDT), Nazdrovje wrote:
>
>
> Hi group,
>
> I was playing with Manipulate and GeometricTransformation and found a
> strange difference in behaviour when manipulating the orientation of a
> circle containing a line depending on how it was drawn. Below, I
> provide two ways of drawing this configuration. The first one behaves
> as expected, but moving the slider in the second example results in
> unexpected size changes.
>
> I suppose it must have something to do with bounding boxes of the
> building blocks, but I don't quite get it. I also feel the behaviour
> of the second one is actually wrong. What do you folks think?
>
> Cheers -- Nazdrovje
>
> This one rotates as expected:
>
> Manipulate[
> Graphics[
> GeometricTransformation[
> {
> Circle[],
> Line[{{-1, 0}, {1, 0}}]
> }, RotationTransform[x]
> ]
> ], {x, -180, 180}
> ]
>
> This one behaves erratical:
>
> Manipulate[
> Graphics[
> GeometricTransformation[
> {
> EdgeForm[Black],
> FaceForm[],
> Disk[{0, 0}, 1, {\[Pi], 2 \[Pi]}],
> Disk[{0, 0}, 1, {0, \[Pi]}]
> }, RotationTransform[x]
> ]
> ], {x, -180, 180}
> ]




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