[vtkusers] Recalculation of contours into an contour representation

[Sven Olaf Lüttmann]

Dear vtk users,
I have a question gerading contours in a 
vtkContourRepresentation.

What I have is a deformed model as vtkPolyData, 
representing an anatomical structure, and a 
corresponding volume dataset (MR-Images).

Now I'd like to recalculate a contour from the 
model of a specific slice in the dataset and pass 
it back to a vtkContourWidget to readjust it again.

Therefore I iterate through all points in my 
vtkPolyData model and compare the z coordinate of 
the point with that from the slice. That is 
already working.
I saw that I can add Points to a contour 
representation by calling 
AddNodeAtWorldPosition(), for example.

Unfortunately that is not working as expected.

Does someone has an idea how to achieve that, is 
there a better way to extract single contours from 
an vtkPolyData model and add them to a contour widget.

Thanks very much for your help
  Sven