[vtkusers] multiple volume rendering

[eugen]

Hello,

at least since 2003 there are questions in this list about how to render  
multiple overlapping volumes.

I realised that vtk does not support such an option, at least it is so  
said in many postings... The main ideas to do such a thing by resample all  
the volumes to one or the like are often suggested but seem more like a  
workaround....

I'm trying to render two volumes that completely overlap each other (CT  
and PET from the same person) and I want to modify their transferfunktions  
independently... resampling is not an option...

So: how can we (I) add "multiple overlapping volume rendering" to vtk? Why  
is that so complicated in vtk (OpenSG and other projects do overlapping  
volume rendering)? Has someone already tried this? Where to start?


Any comments are appreciated!

Eugen