[vtkusers] Overlays and Opacity

[John Biddiscombe]

I'm using two renderers with layer numbers 0 and 1. in the layer 0 renderer,
I'm handling all 2D actors, whereas in layer 1 I'm using normal 3D props.

When I give one of the 3D actors some opacity in it's colour property, it
causes one of the 2D actors to "Disappear". Strictly speaking only some of
the polygons rendered into the overlay plane disappear. It appears to be
position dependent.(only the "first" 2D actor appears to be affected AFAICT)

Could there be something left behind on the opengl stack that's causing
trouble or should I look elsewhere? I'm a bit puzzled. Could even be a
hardware problem.

Anyone got an idea?

JB