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Re: Bug associated with Graphics3D???

  • To: mathgroup at smc.vnet.net
  • Subject: [mg105237] Re: [mg105210] Bug associated with Graphics3D???
  • From: Syd Geraghty <sydgeraghty at me.com>
  • Date: Wed, 25 Nov 2009 02:32:57 -0500 (EST)
  • References: <200911241050.FAA00829@smc.vnet.net>

Wow Lou,

That was a very interesting artifact of Show[].

The key is to be found in the Possible Issues documentation for Show[].

Show uses the options from the first graphic:

So you first have to reverse the order of the shown functions!!!!

Show[Pla[x], Bloid], x]     ......    that fixes the 5.1 issue !!



Do[Print[Show[Pla[x], Bloid], x], {x, 5.05, 5.15, 0.025}];                works fine! 



Cheers .... Syd

Syd Geraghty B.Sc, M.Sc.

sydgeraghty at mac.com

Mathematica 7.0.1.0 for Mac OS X x86 (64 - bit) (12th September 2009)
MacOS X V 10.6.1 Snow Leopard 
MacBook Pro 2.33 GHz Intel Core 2 Duo  2GB RAM




















On Nov 24, 2009, at 5:50 AM, Louis Talman wrote:

> Can anyone explain why the disk that corresponds to x = 5.1 (see the  
> last line of the code below) isn't red---like the others?
> 
> -------------------------
> 
> Rho[Psi_] = 2/(1 - Cos[Psi]);
> 
> Para = ParametricPlot3D[
>    Rho[Psi] {Cos[Psi], Sin[Psi] Cos[Theta], Sin[Psi] Sin[Theta]},
>    {Psi, Pi/3, Pi}, {Theta, 0, 2 Pi},
>     PlotStyle -> {Specularity[0.9], Opacity[0.3]}, Mesh -> None,
>     Axes -> None, PlotRange -> {{-1.3, 6.7}, {-3.5, 3.5}, {-3.5,  
> 3.5}}];
> 
> Focus = Graphics3D[{PointSize[0.015], Point[{0, 0, 0}]}];
> 
> Bloid = Show[Para, Focus];
> 
> Pla[x_] := ParametricPlot3D[
>    x Sec[Psi] { Cos[Psi], Sin[Psi] Cos[Theta], Sin[Psi] Sin[Theta]},
>    {Theta, 0, 2 Pi}, {Psi, 0, ArcTan[(2 Sqrt[3])/x]}, Mesh -> None,
>    Axes -> None, PlotStyle -> {Red, Opacity[0.6]}];
> 
> Do[Print[Show[Bloid, Pla[x]]], {x, 4.8, 5.4, 0.1}];
> 
> ---------------------------
> 
> It also happens when x = 3.5, but for no other values of x generated  
> by {x, 3.0, 6.5, 0.1}.
> 
> 
> --Lou Talman
>   Department of Mathematical and Computer Sciences
>   Metropolitan State College of Denver
> 
>  <http://clem.mscd.edu/%7Etalmanl>
> 
> 
> 


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