[vtk-developers] How to get data from a vtk pipeline ?

[houssen]

How to get data (node coords, node values, cell values for instance) 
from a vtk pipeline (that renders a vtkStructuredGrid for instance) ?

I have a vtkRenderer. From there, I get a list of vtkActor (for me an 
actor identify one pipeline - several actors means several pipelines 
managed by the same renderer : correct ?). From there, for each actor, I 
get a vtkMapper. How to get data "behind" the mapper (the ones created 
by the initial source or reader) as, for instance, a vtkStructuredGrid ? 
I tried vtkMapper::GetInput but I get a crash in several different cases 
I tried. What is the correct way to get the data ? Is there an example 
somewhere ?

Franck