Hi Rouben,
I can confirm that it is some scaling/projection issue.
In the meantime, you may be interested in the option combination
\begin{axis}[...,
scale mode=none,
scale=0.5,
...
]
(without! axis equal).
This will disable most scaling mechanisms, and will use the initial
orthogonal projection as returned from the 'view' key. I will look into
the root cause of the problem.
Best regards
Christian
Am 27.04.2012 16:52, schrieb Rouben Rostamian:
> Thank you, Christian, for looking into this. For now, I will
> try to achieve a realistic projection by tweaking the individual
> axis scales.
>
> Rouben
>
> ---- original message -------------------------------------------
> From: Christian Feuersänger<cfeuersaen...@googlemail.com>
> Date: Fri, 27 Apr 2012 08:01:51 +0200
> To: Rouben Rostamian<rostam...@umbc.edu>
> Cc: PGFplots mailing list<pgfplots-features@lists.sourceforge.net>
> Subject: Re: Plotting a sphere in pgfplots
>
> 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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