[vtkusers] reasons of limitations on opacity per component and up to 4 components in label-map volume rendering?

[terminator]

Hi everyone,
Although subject is clear enough, but I want to know what's the reasons of
these limitations?
I found out that vtk supports up to 4 components in label map volume
rendering (with mask). I can set colors for each component, but just first
opacity (index=0) will applied and others will be ignored. Is there
technical issue for controlling each component opacity separately?
My last question, why number of components is restricted to four? seems the
overhead of a few transfer functions is not too much.



--
Sent from: http://vtk.1045678.n5.nabble.com/VTK-Users-f1224199.html