Valgrind wasn't happy without the initialization
if (isi) {
double x = isi->GetInteractor()->GetEventPosition()[0];
double y = isi->GetInteractor()->GetEventPosition()[1];
if (isi) {
double x = isi->GetInteractor()->GetEventPosition()[0];
double y = isi->GetInteractor()->GetEventPosition()[1];
int VisibleInWindow = this->FindSlicerNumber(isi->GetInteractor()->GetRenderWindow());
vtkRenderer* renderer=NULL;
int VisibleInWindow = this->FindSlicerNumber(isi->GetInteractor()->GetRenderWindow());
vtkRenderer* renderer=NULL;