[vtkusers] InfoVis: Setting vertex color LUT range?

[Eric E. Monson]

Hey Jeff,

Thanks for all the help recently. I'll get around to filing some  
things on Mantis soon...

In the meantime I finally figured out how to get at the vertex lookup  
table in the graph mapper inside the view, and then copy values from a  
color transfer function into the LUT to generate my desired diverging  
color map. I'm still having a problem, though, forcing the scalar  
range of the color mapping. (I want it to be symmetric positive and  
negative, so the middle of my color map sits at zero).

Do you know of any way to force a scalar range on the vertex color map  
(or the VertexMapper within the GraphMapper, whichever is really the  
right way to do it) when using a GraphLayoutView?

Thanks,
-Eric


On Jan 12, 2009, at 9:47 AM, Jeff Baumes wrote:

> Looks like a feature request for vtkViewTheme. We should have made it
> store a general color map, rather than restricting it to HSV ranges.
> It should be a fairly simple fix. The theme would need to store a
> lookup table, and the ApplyViewTheme() function in each view would
> need to use this directly. The old range methods on vtkViewTheme would
> modify its lookup table.
>
> Jeff
>
> On Fri, Jan 9, 2009 at 9:47 PM, Eric E. Monson <emonson at cs.duke.edu>  
> wrote:
>> Hey folks,
>>
>> To color vertices according to an array that contains both positive  
>> and
>> negative values, I need to build a diverging color map (lookup  
>> table) and
>> force the scalar range that's mapped over these colors to be  
>> centered on
>> zero:
>>
>> 1.  If I'm using a vtkGraphLayoutView, is there any way to force  
>> the lookup
>> table to cover a certain range of values (rather than the real  
>> range of the
>> vertex scalar array)?
>>
>> 2.  Is there a way with a theme to set a lookup table that's been  
>> built
>> separately (rather than using ranges for hue, saturation, etc.) for  
>> extra
>> control over the color map?
>>
>> It would be very cool if within a theme, or someplace handy like  
>> that, you
>> could set the scalar range and the "Color Space" like when you use  
>> the Color
>> Scale Editor in ParaView...
>>
>> Thanks,
>> -Eric
>>
>> ------------------------------------------------------
>> Eric E Monson
>> Duke Visualization Technology Group
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>
>
>
> -- 
> Jeff Baumes, Ph.D.
> R&D Engineer, Kitware Inc.
> (518) 371-3971 x132
> jeff.baumes at kitware.com