[Paraview] error with volume rendering

[koala]

hi,all
I got an error when I made the volume rendering.The error message is 

" # Error or warning: There was a VTK Warning in file: /home/myfile/paraview-2.0.1
/GUI/Client/vtkPVDisplayGUI.cxx (1888)
 Sorry.  Unstructured grids with more than 500,000 cells cannot currently be ren
dered with ParaView.  Consider thresholding cells you are not interested in.  "

Why I got this error ? Who can tell me ?
Thank you .
                                  wls
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