[vtkusers] get vtkPolyData from VRML files?

[ChenHao]

i am new user in VTK,here is my question.
How can I get vtkPolyData or vtkActor or something else from a VRML file?
I know vtkActor can be get from vtkRenderer after import a VRML file,but is there any other way to get vtkActor or something else when NOT using vtkRenderer?

Thanks!