[vtkusers] How to access sequentially pointers of vtkPoints data (coordinates) ?

[pof]

Hello,

I need to access (for further use outside of vtk frame) the pointers 
that hold the points data of of vtkPoints set.
So I try using vtkPoints::GetPoint(int id) that is supposed to return 
the pointer I am looking for.

The problem is that I got something wrong at execution :
- if I call GetPoint(Id0) only once for a given Id, this is ok
- but then if I call GetPoint(Id1) a second time (or more) for another Id, 
  all the stored pointers are the same and point to coord vector of the 
last accessed point.
Here below is a small code that reproduce the problem.

I'm obviously missing something but can't figure out what!
Does anybody has got an idea on the mistake I'm doing?

Thanks
JD