[vtkusers] display a thick shell of volume

[Weiguang Guan]

Hi VTK users,

I want to volume render (using 3D texture mapper) a shell with specified 
thickness. Previously, I used vtkClipVolume twice, one clipped away the 
inner portion of a regular volume data, the other clipped away outer 
portion. The only problem is slow rendering speed because the resultant 
data is no longer a regular volume data.

Can anyone suggest a better solution? Would it be faster if I used 
several spheres with texture mapped on them and alpha-blending? Thanks.

Best,
Weiguang