"There was a real train station built in Montreal, but there were missing pieces, including the roof. And there was an empty field surrounding it, so we had to replace it with CG cars and CG parking and the city of Chicago way in the distance. We designed the whole suburb where the action takes place because Glenbrook in the film doesn't really exist so we had to rework and redesign completely. We imagined it being eight miles from downtown Chicago, and we knew the sun was facing northeast so we did it all accurately and up to scale.

"Everything in the train station is CG except for the door step. You don't want to throw the viewer off if they notice something that doesn't look right. For the movie to work, it had to be as transparent as possible. That was the biggest challenge. The other challenge involves the mayhem. The train is about to crash and everyone is running out of the city, so there's lots of traffic and people running around so we had to use Massive isolation for crowd and car behavior. And for the CG parking, everyone has a sense of what it should look like. We even looked at the existing vegetation in Chicago to make sure that it matched in the area that we were in."

The entire train station environment was appropriately Chicago-fied.

Lens distortion proved to be a challenge in matching CG elements with plates. So, to make sure the distortion values were identical, Modus used 3DEqualizer in concert with a special plug-in from La Maison.

In addition, so Modus had to create reflections and shadows of the station and the characters to mirror the movements of the train and the actors in the CG environment.

"We created three techniques," Wilisky explains. "One was a full CG character, such as Jake, that we used as a reflection; the second was a reflection pasted onto surfaces from different angles; and the third was a basic texture applied to a surface of people moving back and forth. All of them were positioned in space, accordingly, so we could get an accurate reflection of the action. And the compositors not only had the layers of all the different actors but also the scene that was already built to scale accurately with all the geometry. This gave them flexibility to move stuff away or create their own map if needed."

And what does Source Code mean to Modus? "Honestly, this one for us is the first time we were the main vendor for something that's more vfx-driven, unlike The American or Barney's Version," Wilisky concludes.

Bill Desowitz is senior editor of AWN & VFXWorld.