[vtkusers] Help(about )

[hbfyf]

Hi!I have tried http://www.vtk.org/Wiki/VTK/Examples/Cxx/PolyData/PolyDataExtractNormals 
 When I used a  correct ply file and run this program ,it says There are 0 points,There are 0 polys,Normals not found!
  
 Can you explain what's wrong with it?Thanks!
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