[vtkusers] vtkRenderWindow()->EraseOff() produces blank window! Why?

[Aroosha Laghaee]

Hello all,

I am transforming and rendering a set of shapes using vtk and would 
like to see the transition of shapes as they are transformed by turning 
the erase option of my render window to off. But this results in the 
render window going blank while the transformations are happening and 
the shapes rendered. I'd be grateful if anyone could tell me what I am 
doing wrong.

         ...
	m_RenWin = vtkRenderWindow::New();
	m_RenWin->SetSize(800,300);
	m_RenWin->EraseOff();

	m_Iren = vtkRenderWindowInteractor::New();
         m_Iren->SetRenderWindow(m_RenWin);
         etc.

Thank you!
       Aroosha