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Re: Problem with 3D Polygon

  • To: mathgroup at
  • Subject: [mg33456] Re: Problem with 3D Polygon
  • From: "Allan Hayes" <hay at>
  • Date: Fri, 22 Mar 2002 04:06:31 -0500 (EST)
  • References: <a79cit$7ug$>
  • Sender: owner-wri-mathgroup at

When showing a Polygon[{p1,p2,p3,p4,}] in 3D, Mathematica superimposes
the insides of the triangles
    Polygon[{p1,p2,p3}], Polygon[{p1,p3,p4}, ....,Polygon[{p1, p(n-1), pn}]
This accounts for the solid rectangle that you get.
How it decides on the edges, or parts of the edges, to show, I have not yet
worked  out in detail but it looks to be based on parts of the line

Allan Hayes
Mathematica Training and Consulting
Leicester UK
hay at
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565

"Kevin J. McCann" <kmccann at> wrote in message
news:a79cit$7ug$1 at
> When I plot the following
> Graphics3D[{LightBlue,
>         Polygon[{{1,0,0},{1,0,1},{-1,0,1},{-1,0,0},{-1/2,0,0},{-1/2,0,
>               1/2},{1/2,0,1/2},{1/2,0,0},{1,0,0}}]}],Lighting->False,
>     Boxed->False];
> I get just a blue rectangle with some of the boundary drawn, not an
> "U" shape. Can someone explain this please.
> Kevin

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