Zbuffer disabled when rendering actor with opacity != 1
This issue was created automatically from an original Mantis Issue. Further discussion may take place here.
The vtkOpenGLActor::Render method disables writing to the zbuffer when the opacity is not 1.0 and it is not picking. This is fine most of the time, except when the render operation has been executed for the specific purpose of getting the zbuffer. For example, we render translucent geometry to the OpenGL backbuffer to get the zbuffer for generating a 2-D mask.
It would be very helpful if a flag was added to vtkOpenGLActor to override this behavior.