VTK issue record -- update of vtkImageData, rendering result unchanged

question:

        Every time you update the content of vtkImageData in the rendering pipeline, you need to regenerate a vtkImageData to replace the original vtkImageData; if not, the rendered image will not change;

reason:

        When the content of vtkImageData being used in the vtk rendering pipeline changes, if the timestamp is not updated using the Modifed method, the rendering result will not change;