Brad Bird gets his shot at live-action action with Mission: Impossible - Ghost Protocol. All images © 2011 Paramount Pictures. All Rights Reserved.

Ordinarily, John Knoll, ILM's senior visual effect supervisor, wouldn't have returned for the fourth installment of the M:I franchise (he worked on the first back in 1996). There are only 700 VFX shots and most are invisible. But this offered the opportunity to work with Pixar's Brad Bird, who was making his first live-action movie. I spoke with Knoll about taking this mission.

Bill Desowitz: You've known Brad Bird for quite some time. But what was it like working with him?

John Knoll: He has all of the important characteristics of a good director: strong story sense, able to get good performances from your actors, and, at least what's' important from my point of view, he's got a good eye for shot composition and visual storytelling. And so, all of those features were on good display on this project. I figured that he would be surrounded by various folks with live-action experience that could get him through the things that are new to him. But the things that are hard to teach he already has very well mastered.

The Burj sequence makes Tom Cruise's Ethan Hunt look like Spider-Man.

BD: What was the hardest learning curve for him?

JK: Probably the biggest part of the learning curve for him was the harsh reality of having to commit to things right then and there when you're shooting live action. And in animation you can often defer decisions or make changes later. After you look at the first version of a scene and make a whole variety of tweaks and changes to iterate on it to get it to your ideal state. And when you're shooting and you only have what you shot to work with and that can be a stressful thing to carefully think everything through.

BD: The Burj sequence is probably the most publicized because of Tom Cruise being such a daredevil up there, but what kind of support work did you provide?

JK: The work there was removing safety equipment, so they erased the cable and the reflection of the cable and IMAX camera. We also shot a glimpse of the Burj ground level for safety and logistical reasons and did CG extensions and the background environment.

BD: What about the approaching sandstorm?

JK: That was done in the Singapore office using our Plume GPU-accelerated simulation rendering application, which is a fantastic tool. It lets you iterate quickly and then generates spectacularly good results. Plume has dramatically changed how we do those fire and dusty things.