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MathGroup Archive 2007

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Re: Problems updating Graphics3D Polygons

  • To: mathgroup at smc.vnet.net
  • Subject: [mg77643] Re: [mg77570] Problems updating Graphics3D Polygons
  • From: DrMajorBob <drmajorbob at bigfoot.com>
  • Date: Thu, 14 Jun 2007 05:28:56 -0400 (EDT)
  • References: <30397362.1181736708391.JavaMail.root@m35>
  • Reply-to: drmajorbob at bigfoot.com

"In[473]:ExpandZ[g_,ratio_]:     
g/.Polygon[pts_]:>Polygon[{#[[1]],#[[2]],#[[3]]*ratio}& /@pts];"

There are a couple of "=" signs missing; not sure what you're seeing at  
your machine.

This works at mine:

Clear[expandZ]
expandZ[g_, ratio_] :=
   g /. Polygon[pts_] :>
     Polygon[{#[[1]], #[[2]], #[[3]]*ratio} & /@ pts];

But I prefer

Clear[expandZ]
expandZ[g_, ratio_] :=
   g /. Polygon[pts_] :>
     Polygon[pts.{{1, 0, 0}, {0, 1, 0}, {0, 0, ratio}}];

Bobby

On Wed, 13 Jun 2007 06:28:25 -0500, chuck009 <dmilioto at comcast.com> wrote:

> Hello guys.  Can you help me write a function which takes a Graphics3D  
> object and multiplies the z-coordinate of each point of all the polygons  
> by a ratio.  This is what I have so far but it's not working:
>
> In[473]:ExpandZ[g_,ratio_]:     
> g/.Polygon[pts_]:>Polygon[{#[[1]],#[[2]],#[[3]]*ratio}& /@pts];
>
> When I test it with this simple Graphics3D object:
>
> gobject=Graphics3D[{Polygon[{{0.,0.5,1.28},{0.,0.,1.},{0.5,0.,1.28},{0.5,
>             0.5,1.64}}],Polygon[{{
> 0.5,0.5,1.64},{0.5,0.,1.28},{1.,0.,2.71},{1.,0.5,3.49}}]}];
>
> It doesn't do anything:
>
> g2=Expand[gobject,2]
> InputForm[g2]
>
> Out[475]â�Æ?Graphics3Dâ�Æ?
>
> Out[476]//InputFormGraphics3D[{Polygon[{{0., 0.5, 1.28}, {0., 0., 1.},
>     {0.5, 0., 1.28}, {0.5, 0.5, 1.64}}],
>   Polygon[{{0.5, 0.5, 1.64}, {0.5, 0., 1.28},
>     {1., 0., 2.71}, {1., 0.5, 3.49}}]}]
>
> I'll keep working on it.  Thanks!
>
>



-- 
DrMajorBob at bigfoot.com


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