Using 3D Game Engines in Architecture?

Mentor asks: "Recently, a very promising young architect asked me to give her some ideas for a design presentation she has to do concerning a new building in Germany. Instead of making another dull non-interactive flyby-drivethrough 3dmax-movie, I suggested using the Halflife or Quake engine to precreate the whole building, and let visitors of the exhibition experience the building firsthand, being a player in it, and interacting with the building (without any actual weapons of course :)). I was wondering whether this has been done a lot already . Does anyone have any tips?" I would think that most 3D engines have evolved enough where something like this might actually be practical. Thoughts?