The Thirteenth Floor
From Simulism
In 'The Thirteenth Floor' (imdb entry), a company develops a machine containing a simulation of the world as it was in 1937. The people in this simulation are unaware of the fact that they are simulated. The simulation is a second degree simulation for the people connecting to the machine, and a first degree simulation for everyone else.
Spoiler warning! If you haven't seen this movie yet, go see it first, then read the rest of this article.
Even though most characters in the simulation are computer-controlled characters, they are still cognitive beings. In the movie, some become aware of the fact that they live in a simulation, by reaching the boundaries of the simulation (a part where the world is rendered only as a wireframe, as depicted in the movie poster).
In The Matrix, when a person is not connected, he is not present in the simulated world. In The Thirteent Floor however, when a person is not connected, his avatar is still present in the simulation: it is controlled by the simulation itself, which gives the character a second personality (they seemingly suffer from a form of schizophrenia).
There is one element in the movie that seems to be non-sensical. Simulated personalities can escape the simulation: if in the simulation a person is killed while he was under control of a real person, the simulated personality takes over the real body outside of the simulation. This is one of the weak points of the movie, as this would seem a technical impossibility.
