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Problems updating Graphics3D Polygons

  • To: mathgroup at smc.vnet.net
  • Subject: [mg77570] Problems updating Graphics3D Polygons
  • From: chuck009 <dmilioto at comcast.com>
  • Date: Wed, 13 Jun 2007 07:28:25 -0400 (EDT)

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??Graphics3Dâ??

Out[476]//InputForm=
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}}]}]

I'll keep working on it.  Thanks!


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