[vtkusers] isosurface rendering extremely slow, is that normal?

[kdsfinger at gmail.com]

hi, all
I use the vtkStripper to display the isosurface of the brain material
of the image size of 256*256*256. My cpu is AMD xp 1.8G with nVidia
graphic card (64M) in a linux box with 1.5G memory. The calculation
time of the isosurface is ok but the rendering time is extremely slow
when I try to interact with the isosurface (moving camera arround). Is
this normal? I understand that the surface of the brain material is
quite irregular. How  can I speed up? Thanks for comments.
zl2k