modo was invaluable in the modeling of the exo-suit, while, in the background, Weta Digital's work on the mothership included modeling and dirt sim challenges.

"Throughout the sequence, from a CG side, he's getting dirtier and more and more damaged with pieces falling off, so the model was constantly being redone. But then from a compositing side, there was a ton of bullet hits that were really hard to get to look right. We had a lot of practice with Iron Man, so we're getting good at that."

As for Weta Digital, Matt Aitken (King Kong, Lord of the Rings) supervised the exterior shots of the alien mother ship and drop ship. "We did the previs and modeling for the exo-suit, which The Embassy took on. At the end, there were some shots that Image Engine couldn't squeeze in, so we did get involved after all. We did about 100 shots. We worked on some really nice sequences, including when the drop ship comes out from underneath the shack and takes off and immediately gets shot down by a missile. And then being tractor beamed up. And any close-ups of the mother ship.

"It was quite a complicated dirt simulation getting that sense of the ground being sliced by the mother ship and crashing. Neill gave us some footage from Iraq of a roadside bomb that doesn't get buried too deep. It just causes this giant mound to rise up, so it became a multi-pass simulation. We drove it with keyframe animation to start off with so that we could shape it and time it. We had to play to the drop ship below but then we ran some in-house dirt simulation tools that we developed. It's a case of running the cracks until that looks good and then baking that and taking that back into the simulation software and running the finer dirt particles and getting [the right] interaction. Drop ship breaks free of the dirt. We structured the event so that it didn't look like a lot of dust swirling around. We wanted it to have some detail in the form and shape.

"The mother ship was a complex modeling and texturing task. We picked up a model that Image Engine had produced and we built that. We did one interior matte painting shot of the hull where the humans find all these huddled mass of aliens. We created that environment and Image Engine did the aliens."

Bill Desowitz is senior editor of AWN and VFXWorld.