To help drive up the buzz around the release of Assassin’s Creed II, Hybride was hiring to create 3 short films to build some backstory and set the mood for the new game.  These 3 films encompassed 750 VFX shots, and in an interview with fxguide they discuss how they did it.

fxg: How did you go about importing those environments?

Raymond: Well, firstly the geometry from the outside world is directly imported from the game engine. Then most of the interior environments were modeled by Hybride. We wrote some software from the between UDA, which is the film division from Ubisoft, and the engineers here at Hybride, to be able to 'borrow' environments from the game engine, Anvil, and to propose them to the director for filming in the studio. Generally we received 4K textures and then after that it was a question for us to re-assign that. We could do more sophisticated lighting than the game engine could take so sometimes we up-rezed the environments.

via fxguide – maya:after effects:avid – Assassin’s Creed.