[vtkusers] Variable transparancy on vtkImageData

[Mark Gooding]

I'm trying to render an image with transpanency proportional to the
intensity the ImageActor input is being produced via
vtkImageMapToWindowLevelColors, and I'm setting a vtkLookupTable for
that. The alpha range of the vtkLookupTable (if set using
SetAlphaRange) seems to make no difference to the transparency of the
final ImageActor.

Is there a limitation in one of these classes which prevents this from
working as I expected?

Once again my searching on the web/this mailing list hasn't helped me
answer this question.

Cheers,

Mark