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<title>Rendering scalar data with NaNs</title>
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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>What would happen if the following occurs (real problem I worked
on a few weeks ago) – a user wants to model a exhaust plume from a power
plant. The model does not go down to the ground. The user then
wanted to plot with line from OUTSIDE of this space , through this space, and
out the other side (which ended up partially filled with nans – I am not
sure if by ParaView, or his simulation code). Would all of this data have
color now, or would it stay transparent?<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Alan<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
vtk-developers-bounces@vtk.org [mailto:vtk-developers-bounces@vtk.org] <b>On
Behalf Of </b>Moreland, Kenneth<br>
<b>Sent:</b> Monday, August 23, 2010 4:30 PM<br>
<b>To:</b> VTK Developers<br>
<b>Subject:</b> [vtk-developers] Rendering scalar data with NaNs<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif"'>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.<br>
<br>
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.<br>
<br>
Does anyone object to these changes, or do they seem reasonable to put into
VTK?<br>
<br>
-Ken<br>
</span><span style='font-size:10.0pt;font-family:Consolas'><br>
**** Kenneth Moreland<br>
*** Sandia National
Laboratories<br>
*********** <br>
*** *** *** email: <a href="kmorel@sandia.gov">kmorel@sandia.gov</a><br>
** *** ** phone: (505) 844-8919<br>
*** web: <a
href="http://www.cs.unm.edu/~kmorel">http://www.cs.unm.edu/~kmorel</a></span><o:p></o:p></p>
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