Cinesite’s VFX Add Finesse to Practical Special Effects in Skyfall

"We started taking reference pictures of the set while they were building it," Neill recalls. "When they started shooting, they had 10 cameras locked off, hanging from the ceiling and coming up from the floor. They shot the actors in the scene one day and the train crash the next day, and the cameras didn't move. The idea was to comp them both together." Green screens were a no-go, because any screen that was hung would get in the way of the view from at least one of the cameras. So Cinesite simply had to roto Bond into the shot. Fortunately, James Bond has short hair and the scene was pretty fast-moving, so the roto job wasn't as demanding as it could have been.
.. HA! I hate roto, read the whole article here , and there's a dope video too!