[vtkusers] Refreshing a filter

[Benjamin Schindler]

Hi

I've searched through the archives and found several people with the 
same problem, but the solution didn't seem to work for me. I'm using a 
qvtk widget to display my data. My data-pipeline is quite simple:

vtkRectilinearGrid->vtkRectilinearGridGeometryFilter->vtkHedgehog->mapper

Now, when I use a slider in my gui, the following gets called:

void TiltVertexScene::valueChanged(int value)
{

   filter->SetExtent(0,grid->GetXCoordinates()->GetSize(), 0,
              grid->GetYCoordinates()->GetSize(), value,value);
   //filter->Modified(); // Already called by SetExtent
   filter->Update();
   container->getRenderer()->Render();
}

However, no update to the screen is visible until I use the mouse to 
drag stuff around. Why is this the case? Which function do I need to 
call so the filter is refreshed? This is on vtk 5.0.4 on linux amd64

Thanks!
Benjamin