Thank you David for your help. the problem that I m meeting now is that the numbers of the normals and vertices are not the same. do you have any idea about this issue. Thank you -- View this message in context: http://vtk.1045678.n5.nabble.com/Vertex-normal-tp3363838p3364550.html Sent from the VTK - Users mailing list archive at Nabble.com.