[vtkusers] Volume rendering with multiple scalars in one vtkImageData

[Charles Boivin]

Greetings,

I have been doing some volume rendering using a vtkImageData as input
for a while now... but I've always only had a single scalar in the
vtkImageData until now. I have now the need to have multiple scalars
in a single vtkImageData structure, and this seems to make my code
crash (i.e. if I pass a vtkImageData with 2 scalars to the volume
rendering classes, it crashes; if there is only one scalar, it works
perfectly).

1) Is this supposed to work, i.e. is this an indication of a problem
elsewhere in my code?

2) If it is possible, is there a way to choose which scalar will be
used by the volume rendering classes?

I've even tried to 'extract' a single array and put that into its own
vtkImageData and feed that to the volume rendering classes -- even
tough it seems that this should work properly, it does not.

Thank you in advance for your answers,

Charles Boivin