Although the tips in the following link are only concerning DirectX9, it may still be useful in Qt:
https://msdn.microsoft.com/en-us/library/windows/desktop/bb147263(v=vs.85).aspx
Notably:
- Only redraw to the image buffer when you need to
- Use smaller textures
- Draw objects from front to back
- Constantly test your code’s performance
- Use one large array/buffer of vertices
- Draw only what needs to be drawn, so culling and z-ordering can only help more
The ideal is to get a higher framerate which is perceivably better experience for the user. For 2D graphics, 16 frames per second is satisfactory. But for 3D graphics, 30 frames per second seems to be tolerable, but 60 frames per second is the minimal. But if you’re just learning 3D graphics programming, don’t worry about frames per second, just worry about the geometry and math to make sure it is correct. Then you can optimize it when you’re confident you understand how it all works.