[Paraview] FPS drop in stereo mode

[Stephan Rogge]

Hello,

I observed an unexpected frame rate drop when using one of PV's supported
stereo modes within an empty scene.

Considering 
* OS: Windows
* V-Sync: On
* Application to display FPS (e.g. www.fraps.com)
* Latest ParaView from git-master 

Following steps should emphasizes the frame rate drop:
1. Open ParaView without any stereo mode
2. Rotate or drag the camera in the 3D view for several seconds and watch at
the frame rate (should be around 60 FPS)
3. Close ParaView
4. Open ParaView with "--stereo" flag enabled
5. Rotate or drag the camera in the 3D view for several seconds and watch at
the frame rate (should be around 22 FPS)

Obviously, stereo rendering should take twice the time of a monocular
rendering. But this should only occurs in more complex scenes. Can anyone
reproduce this behavior? Is this a BUG?

Best regards,
Stephan