Another quick addition which I discovered yesterday is great for pause screens (and some loading screens).
If you want the 3D level to appear static in the background as the 2D loading screen covers part of it, then use 'grabimage' to take a screenshot of it. Then draw the freshly grabbed image in the background before you draw the loading screen (or menu screen) on top of it.
If you're inbetween levels, you can then kill all of the 3D entities, and update the world while the user still sees a picture of the previous level in the background, if that floats your boat.
If you want the 3D level to appear static in the background as the 2D loading screen covers part of it, then use 'grabimage' to take a screenshot of it. Then draw the freshly grabbed image in the background before you draw the loading screen (or menu screen) on top of it.
If you're inbetween levels, you can then kill all of the 3D entities, and update the world while the user still sees a picture of the previous level in the background, if that floats your boat.