[vtkusers] glBlendFunction -- vtkOpenGLRenderWindow (fwd)

[Xenios Papademetris]

A (hopefully) quick question for the VTK/Open GL gurus:

For one of the applications we have here it would be nice if we could
change the Blending Function used for volume rendering using texture
mapping. Reading throught some of the Open GL docs (and having no direct
experince of Open GL -- though I have used Open Inventor in the past) I
discovered that for our problem it would make sense to use an alternative
model of blending ( e.g. CONSTANT_ALPHA) to simularte an x-ray view of the
volume.

I looked through the rendering code and I found what I think is the 
default setting in vtkOpenGLRenderWindow (release version 4.0) to be:

glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );

Is there an easy way of changing this at run-time, without having to 
recompile VTK  again? (That would be a terrible idea as for 99% of what we do the 
defaults are good)

Any help much appreciated,

Xenios

-- 
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Xenios Papademetris		     papad at noodle.med.yale.edu
Associate Research Scientist         http://noodle.med.yale.edu/~papad
Image Processing and Analysis Group, Yale University tel: 203-785-7294
______________________________________________________________________