| Re: Surface plots in spherical coordinates [message #48619] |
Wed, 03 May 2006 17:45 |
Matthias Vigelius
Messages: 2
Registered: May 2006
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Junior Member |
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Hi Rick!
> I can point you to orb__define.pro in your IDL install directory to give
> you an idea of how to do this with a sphere. You may even be able to
thanks for your quick answer! This looks really interesting, so I'll
have to get familiar with object graphics, it seems :-)
cheers,
Matthias
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| Re: Surface plots in spherical coordinates [message #48620 is a reply to message #48619] |
Wed, 03 May 2006 16:53  |
Rick Towler
Messages: 821
Registered: August 1998
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Senior Member |
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You'll get the best results using object graphics. I'm not really a
direct graphics user so I can't really comment on your current approach
but your current code could be modified a bit for OG:
Steps 1-3 would be the same.
The magic would be in step 4. You will create a connectivity array
which connects the vertices you calculated in step 3. I don't have the
IDL docs in front of me but you'll want to search for terms like
"polygon connectivity" and "triangle strips" and "quad strips" and look
for the pages outlining how to construct connectivity arrays. You'll
also want to look at the documentation for IDLgrPolygon.
Step 5 would entail creating a IDLgrPolygon object using the vertices
and connectivity data you created in steps 3 and 4. Then adding that to
an instance of IDLgrModel
Step 6 would be viewing it using xobjview.
I can point you to orb__define.pro in your IDL install directory to give
you an idea of how to do this with a sphere. You may even be able to
modify this for your needs. Note that it's location has moved in the
latest version of IDL:
C:\Program Files\RSI\IDL61\examples\visual <- Pre 6.3
C:\Program Files\RSI\IDL63\examples\doc\objects <- 6.3
-Rick
Matthias Vigelius wrote:
> Hi newsgroup!
>
> Is there a possibility to plot surfaces in spherical coordinates?
>
> I have a function R(theta, phi), describing some kind of elongated
> sphere or an ellipsoid, and I'dlike to plot the surface. What I'm doing
> now is:
>
> 1) create two big vectors theta and phi which sample the sphere, that is
> phi is something like (0, ..., 2*pi, 0, ..., 2*pi, ...) and theta
> (0,...,0,..., pi, ..., pi)
>
> 2) compute R(theta, phi)
>
> 3) convert these coordinates to cartesian
>
> 4) triangulate: triangulate, x, y, tr, b
>
> 5) regrid: grid=trigrid(x, y, z, tr)
>
> 6) draw surface: surface, grid, xc, yc
>
> Besides being quite cumbersome, the problem is that I can't draw closed
> surfaces, say the whole sphere (and even so the results are at best
> moderate).
>
> Is there an easier and working way to do that? I would imagine that this
> is a common task, so I wonder why it does not seem to be supported in
> IDL (or is it?)
>
> Thanks heaps!
>
> Matthias
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