Volume rendering structured grid data...

[Bill Lorensen]

You might be able to "slice" with concentric spheres. Use the combVol script with a sphere for the cut function. I think resulting slices would be spherical.

Bill

At 11:28 AM 10/7/99 -0700, Terry J. Ligocki wrote:
>I need to volume render scalar data lying on a structured grid.  I've
>searched the archived e-mail list and looked at the Vtk documentation
>(book, pamphlet, and man page).  From this I've determined that two
>techniques have been suggested in the past:
>
>    * Resample/splat the data into a structured points form, e.g.
>      "financialField.tcl" and go from there
>    * Slice through the grid, creating planes of polygons, and render
>      these back to front with appropriate colors and opacities, e.g.
>      "combVol.tcl"
>
>In my case, both these techniques are problematic.  I'm looking at
>atmospheric data on the entire globe and, even with an exaggerated scale
>for the atmospheric depth, the structured grid forms a thin shell around
>the Earth.
>
>Thus, in the first technique above the structured points would grossly
>undersampled where the data is or grossly oversampled where the data
>isn't.  The second technique works better in this regard but doesn't
>have a mechanism to recompute the slices as the view moves (at least in
>the example).  Such a mechanism could probably be added but the result
>would be fairly slow (but interesting!).
>
>What I'm looking for is volume rendering for structured grids which is
>interactive (it would be fine if it achieved this via some LOD or model
>switching technique) and produces accurate results (which the user may
>have to wait for once things have stopped moving), i.e. functionality
>like the existing raycasting for structured points.
>
>Is there a way to do this in Vtk?  If not, has anyone written something
>fits in with Vtk and addresses this?  Beyond this, any hints and/or
>comments would be welcome.
>
>Thanks for your time, interest, and help...
>
>                                 Terry J. (Ligocki, tjligocki at lbl.gov)




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