        reader = vtkXMLpoly_dataReader()
        reader.SetFileName(file_name)
        reader.Update()
        poly_data = reader.GetOutput()
    elif extension == '.obj':
        reader = vtkOBJReader()
--
        reader = vtkXMLpoly_dataReader()
        reader.SetFileName(file_name)
        reader.Update()
        poly_data = reader.GetOutput()
    elif extension == '.obj':
        reader = vtkOBJReader()
--
        reader = vtkXMLpoly_dataReader()
        reader.SetFileName(file_name)
        reader.Update()
        poly_data = reader.GetOutput()
    elif extension == '.obj':
        reader = vtkOBJReader()
--
        reader = vtkXMLpoly_dataReader()
        reader.SetFileName(file_name)
        reader.Update()
        poly_data = reader.GetOutput()
    elif extension == '.obj':
        reader = vtkOBJReader()
