[vtkusers] update pipeline

[David Froger]

Hi Shash,

Thanks for the reply.

> Try calling win.Render() in the callback function... The pipeline is
> updated, but it renders only when you explicitly say "Render".

I didn't konw this function, I was trying win.Update()... 

I've added win.Render() in the callback function but the vtkTkRenderWindowInteractor
is still not updated. Something is still wrong or missing...

Isn't the pipeline broken beetween the reader and the mapper?

I also try to add mapper.Update() and renderer.Render()

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