Hi Rouben,
thanks for the illustration... you are right; that is certainly unexpected.
It looks like one of the axes (perhaps y?) has a different scale... which
would mean that the axis equal feature does not what it is supposed to do.
I fear this is a bug a pgfplots (in the axis equal feature). I will look
into it.
Unfortunately, this means that you have to wait for results. The only
remaining option would be to customize the scale of the axes manually.
Pgfplots allows to provide custom (2d projected) axis vectors using
'x=...,y=...,z=...' or to scale the default ones (using the post axis scale
stuff).
Best regards
Christian
2012/4/26 Rouben Rostamian <rostam...@umbc.edu>
> Hi Christian, adding 'axis equal' helps somewhat
> but the image remains an ellipsoid.
>
> An orthogonal projection of a sphere in any direction should
> look like a circle, shouldn't it? What I am getting in pgfplots
> is not a circle. I have attached a sample image produced by
> the following code:
>
> \documentclass{article}
> \usepackage{pgfplots}
> %\usepgfplotslibrary{external}
> %\tikzexternalize
> \begin{document}
> \begin{tikzpicture}
> \begin{axis}[view={60}{30}, axis equal=true]
> \addplot3[surf, z buffer=sort, domain=0:180, y domain=0:360]
> ({sin(x)*cos(y)},
> {sin(x)*sin(y)},
> {cos(x)}
> );
> \end{axis}
> \draw (3.45,2.85) circle(1.8); % for comparison
> \end{tikzpicture}
> \end{document}
>
> Rouben
>
> PS: Changing the view option to `view={45}{0}' produces even
> a more drastic illustration of the flattening of the sphere.
>
> ---- original message -------------------------------------------
> From: Christian Feuersaenger <cfeuersaen...@googlemail.com>
> Date: Wed, 25 Apr 2012 20:37:41 +0200
> To: Rouben Rostamian <rostam...@umbc.edu>, 'PGFplots mailing list'
> <pgfplots-features@lists.sourceforge.net>
> Subject: Re: Plotting a sphere in pgfplots
>
> Hi Rouben,
>
> the result actually *is* a sphere - but the coordinate system is
> skewed because the axes do not have the same units.
>
> The option 'axis equal' for \begin{axis} will fix it.
>
> Best regards
>
> Christian
>
> Am 24.04.2012 03:58, schrieb Rouben Rostamian:
> >Hello Christian,
> >
> >I have a rather basic question about pgfplots.
> >I am trying to plot a sphere, like this:
> >
> >\documentclass{article}
> >\usepackage{pgfplots}
> >\begin{document}
> >\begin{tikzpicture}
> > \begin{axis}[view={60}{30}]
> > \addplot3[surf, z buffer=sort, domain=0:180, y domain=0:360]
> > ({sin(x)*cos(y)},
> > {sin(x)*sin(y)},
> > {cos(x)}
> > );
> > \end{axis}
> >\end{tikzpicture}
> >\end{document}
> >
> >The result appears to be an ellipsoid rather than a sphere.
> >(I am using pgfplots 1.4.1.) I suspect that I have failed
> >to specify an essential parameter. I searched the manual
> >but didn't find the necessary information. Would you please
> >tell me how to make a sphere that looks like a sphere?
> >
> >Rouben
> >
> >
>
>
>
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