Hi, If the *ID* does not exist in polydata.GetCellPoints(*id*, idList), there is a way to trap it? -- View this message in context: http://vtk.1045678.n5.nabble.com/If-ID-not-exist-by-using-polydata-GetCellPoints-id-idList-tp5735223.html Sent from the VTK - Users mailing list archive at Nabble.com.