Thinking about the optimizations that the game probably already does, i'm pretty sure that whenever a room is 'sealed' from the PoV of the player, animations and meshes are turned off. Pathfinding probably never is. But what about: a ) conversations/sounds that the player can't actually hear - say, not in the 'room' the player is or in the sealed rooms adjacent to it b ) physics code that handles niceties like collision beyond the floor or momentum? In fact, why not make the AI 'immaterial' ghosts that can't fall down or collide with anything if the player can't actually see them (problem is, when the player opens a door and suddendly they are penetrating some other object - this needs to be avoided somehow).