[vtkusers] question about rendering

[Niccolo' Camarlinghi]

Dear vtk users,

I'm trying to write an application that shows a 3d surface rendering
using vtkMarchingContourFilter() and a slider (vtkKWScale()) to manage
the isovalue .
For some reason change in the slider has no effect until i click on the
screen.
Is there any way to directly update the window without need to interact
with (e.g. only moving the slider)? 

I allegated the class i'm using, the problematic method is Render()

Best Regards

Niccolo'
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