| Re: 3D plot with correct aspect ratio [message #32289 is a reply to message #32288] |
Thu, 26 September 2002 18:55   |
rmw092001
Messages: 17
Registered: January 2002
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Junior Member |
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David Fanning <david@dfanning.com> wrote in message news:<MPG.17fcda6be56e20b99899c6@news.frii.com>...
> Kristian =?iso-8859-1?Q?Kj=E6r?= (Kristian.Kjaer@Risoe.DK) writes:
>
>> I set up a 3D coordinate system and a projection with
>>
>>
>> range=3D[-7.,7] & az=3D40 & ax=3D35 ;, say
>> surface,dist(4),/nodata,/save,xran=3Drange,yran=3Drange,zran =3Drange,$
>> ax=3Dax, az=3Daz, $
>> xstyle=3D1+4,ystyle=3D1+4,zstyle=3D1+4
>>
>>
>> and then I plot in it with plotS.
>> The x, y and z axes are equivalent and in the same units, =
>>
>> (say, meters) so I want the resulting postscript to be a =
>>
>> true projection (with a known scale factor) of this 3D field.
>> How do I achieve that?
>
> I don't know the answer to this, exactly, without doing
> some research, but I *do* know the answer is NOT to
> pursue this any further with direct graphics. Direct
> graphics uses as 2.5D graphic representation (you notice
> the Z axis is always vertical no matter what rotations you
> do). I think the only way to make this happen is to use
> a true 3D graphics system, which in IDL exists only in
> the object graphics system.
>
> Cheers,
>
> David
3D postscript plots aren't really quantitative - you can't measure
stuff at some "depth" in the plot, like you can measure stuff on a 2D
plot. I'd just use trial and error, adjusting POSITION, RANGE values
to stretch axes until the 3D postscript looks "in proportion". IDL
takes care of plotting correctly in whatever 3D axis system you
choose.
Object graphics is great for true 3D, interactive, animated visuals
(see the examples in IDL demos), and it usually gets recommended by
the best programmers in the group :-) It's also a selling point of IDL
over PV-WAVE.
However, for making good 3D postscript plots on paper - no animations,
widgets, interactivity wanted - direct graphics will do almost
everything...
RW
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