[Paraview] cannot display 3 component volume data

[Lawrence M. Lifshitz]

I have created a 3 component image dataset (.vti format).  I am trying
to read it into paraview so that I can display it as a red/green/blue image.
p. 42 of the ParaView Guide says that this should be possible (for 3 
component
images with unsigned chars for each of the 3 components).

Unfortunately, for some reason I can't even get ParaView to treat this
as a volume data set.  It reads in the data, but when I try to set it to
volume rendering  (Object Inspector->Display tab -> Style -> 
Interpolation -> Volume)
I get the message "cannot volume render since no point (or cell)
data available".   I am getting this message EVEN THOUGH the
"Information" tab of the Object Inspector  says

Type: Image (Uniform Rectilinear Grid)
Number of Cells 10444840
Number of Points 10747904
Memory:  3.15e+01 MB
Data Arrays:
Name: i2idata
Data Type:  unsigned char
Data Ranges:  [0,255], [0,255], [0,255]

This all looks correct to me.
The extents and bounds are also correct.

So, why, if all this info looks correct, is it saying it doesn't
have any point data?

I did create the dataset with my own software, so it is possible
that something in the format is wrong; but it couldn't be very
wrong if all the display info looks fine.  I also use this software to
create 1 component signed short data volumes, and those work
fine (i.e., I can set the display style to "volume").

Alternatively (or maybe better) I would be happy reading in
3 images and using different colormaps on each one.  Can ParaView
handle multiple colormaps with the image volumes superimposed?
Or even in separate windows (I've tried fooling around with that but
it seems like it each colormap which gets presented is not independent
of the others, but not quite identical either; I can't interpret exactly
what it thinks it is doing)?

Thanks for any help.

  Larry

(I am using ParaView 3.4.0 on Fedora 11 64 bit system).


-- 
Lawrence M. Lifshitz, Ph. D., Associate Professor
Biomedical Imaging Group (http://invitro.umassmed.edu)
University of Massachusetts Medical School (http://www.umassmed.edu)
Phone: (508) 856-3392   email: Lawrence.Lifshitz at umassmed.edu
Fax:   (508) 856-1840     web: http://invitro.umassmed.edu/lml