I'm working with OpenSceneGraph 3.0.1 (the latest stable) and Qt. OSG has a module named osgQt to create a widget for OSG rendering. I have noticed a strange frame rate drop switching from Qt 4.7 to 4.8. With 4.7.3, the frame rate was maximum 60fps on every computer. With 4.8 the frame is maximum 38-40fps on every computer. Definitely too much to accept. I cannot understand why! Is it a bug or what?
With Qt 4.8.1 now I'm back to 60fps!