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

*To*: mathgroup at smc.vnet.net*Subject*: [mg116365] Re: 3D surface plots - non deletion of data inside*From*: Heike Gramberg <heike.gramberg at gmail.com>*Date*: Sat, 12 Feb 2011 05:18:02 -0500 (EST)*References*: <201102110919.EAA08103@smc.vnet.net>

The anomalies in GL2 are caused by the fact that your function is undefined in the values for ph and th for which Cos[ph+th]==0. Excluding those points from your domain, e.g. by using the option Exclusions -> {Cos[ph+th]==0} in ParametricPlot3D, should get rid of those. Heike. On 11 February 2011 09:19, Narasimham <mathma18 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 >

**References**:**3D surface plots - non deletion of data inside undesirable Range***From:*Narasimham <mathma18@hotmail.com>