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From: David Park on 16 Jun 2010 05:36
The "More Information" for the GeometricTransformation function states:



"Normal[expr] if possible replaces all GeometricTransformation[Subscript[g,
i],\[Ellipsis]] constructs by versions of the Subscript[g, i] in which the
coordinates have explicitly been transformed."



I just wonder if "if possible" means "never" because here is about as simple
a case as one can get.



gr = Line[{{0, 0}, {1, 0}, {1, 1}, {0, 1}, {0, 0}}];



Graphics[{gr, Red,

GeometricTransformation[gr, TranslationTransform[{.5, .5}]]},

Frame -> True]



Now try to make the translation explicit by using Normal.



GeometricTransformation[gr, TranslationTransform[{.5, .5}]] // Normal



It does nothing. There are cases where it would be useful to have the actual
transformed points. Any ideas on how to make this work?





David Park

djmpark(a)comcast.net

<http://home.comcast.net/~djmpark> http://home.comcast.net/~djmpark/

From: Peter Breitfeld on 17 Jun 2010 02:03

That's strange, but you could use a TranformationFunktion to get the
explicit coordinates:

tf=TranslationTransform[{0.5, 0.5}]
tf/@gr
Out= Line[{{0.5, 0.5}, {1.5, 0.5}, {1.5, 1.5}, {0.5, 1.5}, {0.5, 0.5}}]

//Peter

"David Park" wrote:

> The "More Information" for the GeometricTransformation function states:
>
>
>
> "Normal[expr] if possible replaces all GeometricTransformation[Subscript[g,
> i],\[Ellipsis]] constructs by versions of the Subscript[g, i] in which the
> coordinates have explicitly been transformed."
>
>
>
> I just wonder if "if possible" means "never" because here is about as simple
> a case as one can get.
>
>
>
> gr = Line[{{0, 0}, {1, 0}, {1, 1}, {0, 1}, {0, 0}}];
>
>
>
> Graphics[{gr, Red,
>
> GeometricTransformation[gr, TranslationTransform[{.5, .5}]]},
>
> Frame -> True]
>
>
>
> Now try to make the translation explicit by using Normal.
>
>
>
> GeometricTransformation[gr, TranslationTransform[{.5, .5}]] // Normal
>
>
>
> It does nothing. There are cases where it would be useful to have the actual
> transformed points. Any ideas on how to make this work?
>
>
>
>
>
> David Park
>
> djmpark(a)comcast.net
>
> <http://home.comcast.net/~djmpark> http://home.comcast.net/~djmpark/
>

--
_________________________________________________________________
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de

From: Mark McClure on 21 Jun 2010 02:12
On Wed, Jun 16, 2010 at 5:36 AM, David Park <djmpark(a)comcast.net> wrote:
> The "More Information" for the GeometricTransformation function states:
>
> "Normal[expr] if possible replaces all GeometricTransformation[Subscript[g,
> i],\[Ellipsis]] constructs by versions of the Subscript[g, i] in which the
> coordinates have explicitly been transformed."
>
> I just wonder if "if possible" means "never" ...

I complained about this very issue to Wolfram technical support back
in version 6.0. As far as I can tell, nothing has been done about it.
Of course, it's fairly easy to implement on your own but, then, it
should be very easy for Wolfram to get it to work as advertised. It
would also be quite convenient, particularly with the proliferation of
Graphics primitives.

Mark McClure

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