Actually, it's a macro in my old cartogrphy toolkit. It and the other projections use warping of positions along the lines that Randall suggests. The first input has to be the field. Take a look at the tutorial for these tools, which outline both 2d and 3d examples.
http://www.research.ibm.com/dx/proceedings/cart/tutorint.htm
and a sample application at:
http://www.research.ibm.com/dx/proceedings/cart/ozone.htm
Although these tools and applications date back almost a decade, they should still work.
I'm not sure what version you have. There is one at http://www.research.ibm.com/dx/bonuspak/html/bonuspak222.html
It plus a whole bunch of applications and data are available at:
http://opendx.npaci.edu/bin/dx_examples.tar.gz
You might want to use GeoCamera and the Sequencer to rotate your sphere like http://www.research.ibm.com/people/l/lloydt/atwt.gif or http://www.research.ibm.com/people/l/lloydt/atwt.mpg
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Subject: [opendx-users] Re: sphere module
Marissa Forbes:
|I am now looking to have it done in an actual spherical shape that
|rotates)
I can't speak to the Carto package and Sphere, but if mapping to a perfect
sphere is all you need:
- Mark("positions")
-> Compute( "[a.x*3.14159/180, a.y*3.14159/180]" )
-> Compute(
- "radius * [ cos(a.x)*cos(a.y), sin(a.x)*cos(a.y), sin(a.y) ]" )
->
probably want to mix them into "radius".
If you need something more accurate, there's the ChangeProjection module
which is built on the USGS projlib.
To rotate the sphere, you can rotate the sphere with a similar technique,
or just rotate the camera about the sphere. Basically the same but the
latter is cheaper and simpler to tweak (feed a custom "from" point into
Camera, derived from a Compute off a ForEachN or Sequencer module).
There's also the Rotate module which is a faster variation on the former.
Randy
--
Randall Hopper (mailto:[EMAIL PROTECTED])
Lockheed Martin Operation Support
EPA Scientific Visualization Center
US EPA N127-01; RTP, NC 27711
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Subject: [opendx-users] sphere module
Hi everyone-
I am working with three dimensional data that measures a certain gas at
different latitudes, longitudes, and heights (in the atmosphere). I have
successfully visualized the data using the "slab" module, which shows the
gas at one specific height and all lats and lons. I recently downloaded
the cartographic dx bonuspak, and am now interested in showing the
same data on or over the globe. (In my existing visualization, I have the
map projected onto the slab, but I am now looking to have it done in an
actual spherical shape that rotates) When I replace the "slab" module
with "sphere" I get the message:
"ERROR: Sphere: Compute: Bad parameter: Input 0 used in _expression_ and
supplied as NULL"
and the same message appears if I try to put the "World Map Projections"
onto a sphere as well. I am clearly going about this the wrong way. Any
help in turning my flat visualization into a rotating sphere would be
greatly appreciated!
Thanks,
Marissa Forbes
