Doomsday Engine

When 3D models are in use, they may have client-side animations and scripted behavior that the game is not aware of. This information would be lost when saving and loading a game. The engine needs to serialize and insert its own internal state when the game is writing a save.

In practice, the internal state is written in a new file inside the save archive. If missing, the loader will simply fall back to the old behavior of resetting the internal state of objects when loading a save.