[vtkusers] Worked around volume issues but is this a bug?

[Alex Lear]

I was previously having volume rendering problems because vtkScalars are no 
longer supported in VTK 4.0.  I switched to vtkFloatArray but the volumes 
flickered or did not show up at all.  I have since switched to 
vtkUnsignedCharArray because my old scalars where unsigned chars.  This type 
of data works :)  However, it would have been nice to use a float type this 
time around. 

Are float types not allowed for volume values, might there be something else 
I am doing wrong, or maybe a bug?

For reference, I (basically) start with a 3d structured points and apply the 
scalar values to them, then input those to the volume mapper.

Thanks,
Alex Lear