[vtk-developers] Transparent LookupTables

[Biddiscombe, John A.]

vtkLookupTable does not directly support the handling of tables with transparency which changes on a per item level.

I recently added some tweaks to it to allow some pictures to be generated (from paraview) which used an overlay of a dataset which had transparent regions on top of a textured image. It looked very nice, but I was very surprised that there is no native support for generating a lookuptable with a luminance scaled opacity or other similar simple opacity function.

I used to do this quite a bit and found it very useful  (GIS stuff in particular).

Is there some other support for creating semi-transparent datasets/images etc that I have not seen. Has anyone else worked on this. When creating the original point sprite mapper, I had to make a few changes to how the mappers decide if an actor has transparency or not. Normaly they query the actor's opacity, but when it is 1.0 and the lookup table has some, things broke. I know that Francois (or someone else) recently added a native handling for this kind of check within the rendering pipeline, so does support for transparent lookuptables now exist too - and am I looking in the wrong place? 
Either way - is anyone else interested in this capability?

JB

-- 
John Biddiscombe,                            email:biddisco @ cscs.ch
http://www.cscs.ch/
CSCS, Swiss National Supercomputing Centre  | Tel:  +41 (91) 610.82.07
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