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RE: ParametricPlot3D is buggy


Will,

This does look like a bug in the Mathematica graphics. For some reason
Mathematica's algorithim for automatically picking the PlotRange has
misfired.

plot2 = ParametricPlot3D[{Cos[t]Cos[u], Sin[t]Cos[u], Sin[u]},
{t, 0, 2Pi}, {u, -Pi/2, Pi/2}, PlotPoints -> {7, 3}, PlotRange ->
Automatic];

(a plot but no polyhedron)

FullOptions[plot2, PlotRange]
{{-1.05, 1.05}, {-3.141996211819542*^-15,
   2.131357156737179*^-15}, {-1.05, 1.05}}

You will get a proper plot if your choose PlotRange -> All.

Of course, you are using ParametricPlot3D to render polyhedrons by using a
low number of plot points. ParametricPlot3D probably wasn't designed with
that in mind. But PlotRange -> All or a specific PlotRange should solve the
problem.

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/

> -----Original Message-----
> From: Will Self [mailto:wself at msubillings.edu]
To: mathgroup at smc.vnet.net
> Can anyone explain this bug that appears in ParametricPlot3D
> in my version of Mathematica 4.0.2 on Windows 2000?
>
> -----------------------------------------------------------
>
> This works fine:
>
> ParametricPlot3D[{Cos[t]Cos[u], Sin[t]Cos[u], Sin[u]},
> {t, 0, 2Pi}, {u, -Pi/2, Pi/2}, PlotPoints -> {8, 3}]
>
> But this doesn't give a picture:
>
> ParametricPlot3D[{Cos[t]Cos[u], Sin[t]Cos[u], Sin[u]},
> {t, 0, 2Pi}, {u, -Pi/2, Pi/2}, PlotPoints -> {7, 3}]
>
>




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