[vtkusers] How do I make a renderer transparent ?

[de Boer Ingo]

Hi all,

I have a question about making a renderer transparent:
There are two renderers, like

m_pvtkRendererA->SetViewport(0.0, 0.0, 1.0, 1.0);
m_pvtkRendererB->SetViewport(0.0, 0.8, 0.2, 1.0);

m_pvtkRendererB should be transparent because it cuts the
objects from m_pvtkRendererA ?

Is there a way ?

greets
  Ingo