On Fri, Sep 9, 2011 at 11:54 AM, Luigi Laneve <luigi_laneve at hotmail.com> wrote: > Thank you for your reply! > Nothing happens; SS is NULL yet! What is vtkSource? Don't you just want to get your data? vtkMapper* map = actor_sphere->GetMapper(); vtkDataSet* SS = map->GetInput(); this SS pointer is now non-null. David