       Re: 3D surface plots - non deletion of data inside undesirable Range

• To: mathgroup at smc.vnet.net
• Subject: [mg116373] Re: 3D surface plots - non deletion of data inside undesirable Range
• From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
• Date: Sat, 12 Feb 2011 05:19:28 -0500 (EST)
• References: <ij2uvf\$7u3\$1@smc.vnet.net>

```Just add an exclusion to the second graph and you're set:

GL2 = ParametricPlot3D[gl, {th, -Pi/3, Pi/3}, {ph, -Pi/3, Pi/3},
PlotRange -> {{-3, 3}, {-3, 3}, {-3, 3}},
Exclusions -> Cos[ph + th] == 0]

The problem here is the division by zero in places where Cos[ph + th]
== 0.

Cheers -- Sjoerd

On Feb 11, 10:19 am, Narasimham <mathm... at hotmail.com> wrote:
> a=2;b=1;c=3;gl={a Cos[ph-th],b Sin[ph-th],c Sin[ph+th]}/Cos[ph+th=
];
> GL1=ParametricPlot3D[gl,{th,-Pi/4,Pi/4},{ph,-Pi/4,Pi/4},PlotRange->{{-3,3},{-3,3},{-3,3}}]
>
> GL2=ParametricPlot3D[gl,{th,-Pi/3,Pi/3},{ph,-Pi/3,Pi/3},PlotRange->{{-3,3},{-3,3},{-3,3}}]
>
> Show[GL1,GL2]
>
> Extended plot limits in GL2 beyond those of GL1 result in 3D plot that
> fail to delete undesired spurious tracing/tracking data between points
> not lying on the required surface.Like 'pen up' data in earlier
> graphing s/w. It is OK may be to plot an enclosed solid, but not for a
> surface. The difficulty also appeared in earlier Mathematica versions.
> Is there then, no work around possible?
>
> Best Regards
> Narasimham

```

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