Re: [netcdfgroup] Creating a NetCDF file for VisIt with an unstructured grid

  • To: Tim Duly <duly2@xxxxxxxxxxxx>
  • Subject: Re: [netcdfgroup] Creating a NetCDF file for VisIt with an unstructured grid
  • From: Rich Signell <rsignell@xxxxxxxx>
  • Date: Tue, 27 Mar 2012 13:19:02 -0400
Tim,

If you want to use VisIt with NetCDF files, you have to know what
conventions VisIT expects so you can create VisIT-compatible NetCDF
files.   I seem to remember that they implement some of the CF
conventions, but not all.  The VisIt developers or community should be
able to help you with this.

-Rich


On Tue, Mar 27, 2012 at 10:50 AM, Tim Duly <duly2@xxxxxxxxxxxx> wrote:
> Rich,
>
> Thank you for the information.  My data comes from an unformatted Fortran
> file, and Python was the easiest way to read this data.  I'd prefer to use
> VisIt as I'd like to extend this project with a 2D plot with time, and then
> to a 3D plot with time.
>
> Perhaps I wasn't clear enough-- I have all the data read into Python right
> now, but am having trouble writing the coordinate information into the
> NetCDF.  I am able to get the actual data into VisIt, but it's not "applied"
> to the (200 x 100) matrix X and Y coordinate information.
>
> From my research, it doesn't look like NetCDF is able to do this.  Perhaps I
> should be using another data format for VisIt?
>
> Thanks,
> Tim
>
>
>
>
> On Tue, Mar 27, 2012 at 9:20 AM, Rich Signell <rsignell@xxxxxxxx> wrote:
>>
>> Tim,
>>
>> You mention quite a few things here: unstructured grids, Matlab,
>> NetCDF, CF, Python and Visit.
>>
>> If your goal is to truly to visualize unstructured grid data from
>> NetCDF files (or OPeNDAP datasets) using Python, take a look at this
>> screen shot using Mayavi2
>>
>> http://dl.dropbox.com/u/12710282/Screenshot-Mayavi.png
>>
>> and the simple code that produced it:
>>
>> http://dl.dropbox.com/u/12710282/triangular_mesh_demo.py
>>
>> Mayavi2 comes with at least two scientific Python distributions:
>> Python(x,y) (free, works on 32 bit windows) and the Enthought Python
>> Distribution (free for educational use, works on 32/64 bit windows,
>> mac and linux).  You should be able to run the above python script
>> without changes on either distribution.
>>
>> However, it sounds like you actually have structured grid data in a
>> text file that you want to use.   In python, I would use numpy
>> "genfromtxt" to read from the text file, and visualize with Mayavi2's
>> "surf" function.  See:
>> http://github.enthought.com/mayavi/mayavi/auto/examples.html
>>
>> If you want to save your data in a NetCDF file, I'd use the
>> NetCDF4Python package (also included in the above scientific python
>> distributions).   This would allow you to visualize it in other tools
>> as well, like Unidata's IDV.
>>
>> Good Luck,
>> -Rich
>>
>> On Mon, Mar 26, 2012 at 3:31 PM, Tim Duly <duly2@xxxxxxxxxxxx> wrote:
>> > Hello,
>> >
>> > I have a relatively simple task. I have 2D data, of dimension 200x100
>> > that
>> > belong to an unstructured grid that contains X and Y, both of which are
>> > dimension 200x100.  In other words, I have DATA = f(X,Y).
>> >
>> > I'm trying to plot this in VisIt, but am having a tough time applying
>> > the
>> > unstructured grid to the actually data.  In MATLAB, for example, this is
>> > easily accomplished with surf(X,Y,DATA), but I'm having difficulties
>> > finding
>> > the equivalent in NetCDF.  How do I do this?  Is this problem solved in
>> > NetCDF or in VisIt?
>> >
>> > I am using the Python library NetCDF to transform unformatted Fortran
>> > data
>> > into NetCDF format.  I have read this page
>> >
>> > ( http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.4/cf-conventions.html#id2984605 ;)
>> > but I do not understand how to do this with the NetCDF library in
>> > python.
>> >  Should I use another data format besides NetCDF?
>> >
>> > Any help would be greatly appreciated.
>> >
>> > Thanks,
>> > Tim
>> >
>> > _______________________________________________
>> > netcdfgroup mailing list
>> > netcdfgroup@xxxxxxxxxxxxxxxx
>> > For list information or to unsubscribe,  visit:
>> > http://www.unidata.ucar.edu/mailing_lists/
>>
>>
>>
>> --
>> Dr. Richard P. Signell   (508) 457-2229
>> USGS, 384 Woods Hole Rd.
>> Woods Hole, MA 02543-1598
>
>



-- 
Dr. Richard P. Signell   (508) 457-2229
USGS, 384 Woods Hole Rd.
Woods Hole, MA 02543-1598



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