Scratchings from whiteboard:

Main application loop:

  for( ;; )
  {
      CameraGroup::sync();
      preCull Traversal;
      CameraGroup::frame();
  }

CameraGroup::frame()
{
     Barrier.release();
}

CameraGroup::sync()
{
    Barrier.wait();
}


Two possible Camera implementations:

A) ======

Camera::thread()
{
    for( ;; )
    {
	Barrier.wait();
	cull();
	SVR(); // Sync Vertical Retrace
	draw();
	Barrier.release();
	swapbuffers();
    }
}


B) ==== Threaded Cull 

Camera::thread()
{
    for( ;; )
    {
	Barrier.wait();
	CullDrawBarrier.release();
	CullDrawBarrier.wait();
	swap scene view buffers;
	Barrier.release();
    }
}

Cull::thread()
{
   for( ;; )
   {
       CullDrawBarrier.wait();
       cull();
       CullDrawBarrier.release();
   }
}

Draw::thread()
{
    for( ;; )
    {
	CullDrawBarrier.wait();
	draw();
	CullDrawBarrier.release();
    }
}