[vtk-developers] Rendering scalar data with NaNs

[Moreland, Kenneth]

I've recently run into an issue with rendering fields with NaN values in it.  In this case, the data comes from a simulation that intentionally writes out NaN values, which have a significant meaning.  The problem is that the current VTK rendering classes have no control over what color the NaN values map to, and I have noticed that different hardware maps them differently.

Thus, I propose making the changes in the attached patches (created with git-format-patch).  First, a NanColor was added to vtkLookupTable (as a 4-tuple RGBA) and added to vtkColorTransferFunction (as a 3-tuple RGB) so that these respective lookup tables would return a specific color for NaN.  Next, vtkScalarsToColorsPainter was modified to use a 2D texture map that uses the second dimensions to distinguish between real and NaN values.  I also added a test for rendering these NaN values along with the other non-finite -INF and INF values.

Does anyone object to these changes, or do they seem reasonable to put into VTK?

-Ken

   ****      Kenneth Moreland
    ***      Sandia National Laboratories
***********
*** *** ***  email: kmorel at sandia.gov
**  ***  **  phone: (505) 844-8919
    ***      web:   http://www.cs.unm.edu/~kmorel

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