[vtkusers] updating vtkImageData ?

[David Doria]

>
>
> It turns out there is some subtle difference between
> vtkRenderer.Render() and vtkRenderWindow.Render()
>
> This example shows the behavior:
> http://pastebin.com/KPFpkCKU
> On my machine I see an unmodified image with "renWin.Render()" and a
> modified image with "ren.Render()"
> I had previously used renWin.Render() in all my vtk code, but I have
> always worked with polydata only.


Quoting David Gobbi from an old mailing list post that I've used ever since:

"You should never, ever call renderer->Render().  That method is only
meant to be called by the vtkRenderWindow.  The documentation says
so quite clearly.  By calling it you are probably causing some timestamps
to be set (indicating that all actors in the renderer have rendered), but
you
aren't actually doing any rendering.  Then, when you call
renderWindow->Render() it sees that those timestamps have been updated
and thinks that there is nothing to be done."

I'm not sure why renderWindow->Render() is not working for you in this
case. Any Python VTK experts out there?
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