Re: [Gnuplot-info] how to draw a sphere that looks like a round sphere

[Thomas S. <t.s...@fz...>]

i uploaded this patch to sourceforge:

http://www.nabble.com/file/p23737622/graph3d.patch graph3d.patch 


Thomas Sefzick wrote:
> 
> oh, what's that?
> seems that there is an offset somehow reciprocal to the axis length.
> 
> this simple example shows the problem:
> 
> set view equal xyz
> set xrange [-0.2:0.2]
> set yrange [-1:1]
> set zrange [-1:1]
> splot sin(x**2+y**2)
> 
> has to do something with the calculation of 'xcenter3d', 'ycenter3d'
> and 'zcenter3d' in 'graph3d.c'.
> i'll try to find out how it works...
> 
> 
> renzresearch wrote:
>> 
>> Thank you Thomas,
>> 
>> It works well for me.  One additional question: how does
>> gnuplot decide the rotation center of a 3D object?  For
>> example, if I do 'splot 0.2*cos(u)*cos(v), cos(u)*sin(v),
>> sin(u)', the 3D oval swings from one side of my window to the
>> other when I rotate it.  If I do 'splot 0.1*cos(u)*cos(v),
>> cos(u)*sin(v), sin(u)', the object swings in and out of the
>> window.  Can I specify a rotation center?
>> 
>> Zhong
>> 
>> 
>> ---- Original message ----
>>>Date: Fri, 22 May 2009 12:55:49 -0700 (PDT)
>>>From: Thomas Sefzick <t.s...@fz...>  
>>>Subject: Re: [Gnuplot-info] how to draw a sphere that looks
>> like a round sphere  
>>>To: gnu...@li...
>>>
>>>
>>>start with a graphics window which is a square:
>>>set term <terminal_type> size <XX>, <YY>
>>>with XX = YY
>>>
>>>set view equal xyz
>>>
>>>set xyplane relative 0.0
>>>
>>>
>>>renzresearch wrote:
>>>> 
>>>> The sphere I draw in parametric mode looks flattened in z
>>>> direction, even I use 'set view equal xyz'.
>>>> 
>>>> I managed to use 'set view equal xy' and 'set view' to change
>>>> scale and scale_z.  My sphere is now close to round.  The
>>>> problem is that its vertical size keeps changing when I spin
>>>> the sphere or resize the window.
>>>> 
>>>> Could someone give a hint?  There must be a simple option to
>>>> make a sphere a perfect sphere no matter how you look at it.
>>>> 
>>>> Zhong
>>>> 
>>>>
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>>>
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> 
> 

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