Going More Real World on <em>Iron Man 2</em>

Check out the Iron Man 2 trailers at AWNtv! [1]

For Iron Man 2, director Jon Favreau not only wanted to ramp up the jeopardy and emotional crises for his armed and animated [2] superhero, but also the action, too. Thus, there's the addition of pal Rhodie as War Machine (Don Cheadle) as well Whiplash (Mickey Rourke) and military drones created by arch rival Justin Hammer (Sam Rockwell). ILM worked on 535 out of 1,000 shots, collaborating with ILM Singapore (under the leadership of Mohen Leo [3]), which contributed roto, layout, matchmove suit animation and compositing throughout. ILM also worked directly with Embassy Effects, Trixter and Pixomondo. However, Janek Sirrs, the overall visual effects supervisor, contracted several other studios for additional work, including Double Negative, Legacy, Pixel Liberation Front, Fuel, Lola, Evil Eye, Goat, Svengali, The Third Floor, Prologue, Hydraulx and Perception, among others.

"Jon was more aware of how we were able to get to the suits so we were a lot closer for a lot longer," states Ben Snow [4], visual effects supervisor for Industrial Light & Magic. "Basically, all but three or four of the shots where the helmet's shut are completely CG. And then when the helmet's open in the house fight between Iron Man and War Machine, it's often using a partial suit that Legacy Effects created but then extending that with arm bits and other bits and sometimes the whole suit replaced, depending on the shot. We were also able to use some of the new lighting tools that we started developing on Terminator Salvation [5] and did a lot of work to make that a more usable and real world-like [system] for Iron Man. We were able to leverage the improvements in lighting to give us a bit more creative freedom."

Indeed, that's probably the biggest breakthrough for ILM on Iron Man 2: On Terminator Salvation, the studio integrated an energy conserving shader set in RenderMan in conjunction with an HDRI lighting approach to get rendered images with a more believable real world look.

The system is called Energy Conserving Image-Based Important Sampled Lighting and what it means is "that the way we're lighting the CG suit is a lot more like the way the DP [Matthew Libatique] lights the real suit and we're using photographs of his to light the CG suits and bounce lights and flags to flag off lights. And what we found in practice is that we go from zero to real a lot more quickly and so we were able to focus on the aesthetic stuff: How do we make it look more beautiful and tweak the lighting so it fits in better?"

For example, when you have such a reflective silver suit during the house fight, Doug Smythe, the digital production supervisor, helps make it easier for the TDs to create a dynamic environment map to include not only the other character but also his shadows as well. "We're still dealing with expensive ray tracing and expensive indirect," Snow adds. "We're still in RenderMan [6], but for some of it we used mental ray [7]. I actually lit a shot myself during the freeway chase, and it was, to my mind, a lot more intuitive, much more like what I'd see on set using the lights. What's interesting for a lot of the artists is they're so used to using spotlights and ambient occlusion that it's conceptually weird to them initially. You're so used to the cheats. A lot of times a CG artist will turn off expediential fall off or real world-type fall off on the light so it doesn't dim out properly as you get farther away. Well, in this lighting skill, we don't have that control: if it's going to fall off, you have to boost the light's intensity, as we do on set. It does require you to think more physically correctly, but I do think that contributes to everything feeling more realistic."

Tasked with bigger and more complex action sequences, ILM used a bigger box of tools in terms of simulations, fluids and destruction.

"We leveraged improvements we've made to our internal sim engines, so we had the hydraulic fluids during the end fight and we had to add water droplets on the suits as they roll around in the water, so that's using some of the PhysBAM stuff that's getting better," Snow continues. "For the fireplace explosion, we were also able to build on some practical elements with some fluid-simulated fire where the two suits face off against one other and the RTs interact to make the effect of where the air vaporizes and create a shockwave."

The other key leverage opportunity was a greater use of Nuke [8] and its 3D compositing capabilities, which allowed ILM to blur the line between digital mattes and compositing a lot more. This was important because there were a lot more synthetic environments and environment extension such as the climactic battle in the Japanese Garden (shot in LA) where Iron Man and War Machine face off against the drones and Whiplash.

"Out of the box, the compositor could start out with a pretty nice smoky-looking environment and mix that with volumetric-type effects for god rays coming through the smoke and rendered 3D atmospherics to create a texturally dense and interesting [look]," Snow explains. "It freed us up to make some more creatively interesting environment work."

Favreau was also encouraging about ILM's involvement in the art direction, including the arsenal of weapons for War Machine and the drones created by Bruce Holcomb, the model supervisor, and Aaron McBride, the VFX art director.

"Weapons for War Machine and Hammer drones were based on real modern weapons and ILM created style sheets, particularly since the drones were associated with a branch of the services," Snow suggests. "The Naval drones had mounted missiles similar to what you'd find on battleships; and the Air Force drones, they'd be based on a sidewinder missile. The looks of the suits were based on the branch of service as well. For the Air Force drone, they went with an F22 stealth paint look that's completely non-reflective and allows the plane to not be radar-detected. But it was so well camouflaged that you couldn't see it in shots. So we had to go back and actually dumb-down the materials just a bit and made it more reflective than you actually want if you're trying to hide your Air Force drones. The signatures of the weapons -- the muzzle flashes, tracers and the look of explosions -- were a challenge, too."

Meanwhile, Marc Chu [9], the animation supervisor at ILM, was tasked with better performances. "We couldn't really see their faces, so [we] worked on making their fighting styles very distinctive and making them act like different characters," Chu says. "Iron Man (who's refined in a completely new suit and has more over-the-top weapons) was the most nimble and flexible of the group whereas War Machine was more brute force. And with Whiplash, we wanted to emphasize the whips and did a lot reference for that. We really wanted to go for a samurai-like feel, reusing drone armor [for the final battle]."

ILM made full use of Imocap this time. "It's tough to meld a performance of Robert with a CG suit and make it look natural, especially when there is such a big height difference between the suits and the actors," Chu continues. "And in some cases, Jon wanted to change some of the nuance of performance as well with a hand gesture. Well, Robert is very animated, so sometimes we wanted to tone that down a tiny bit. This gave us that flexibility."

Apparently Whiplash's hand-crafted suit for the final battle was a last minute addition that required 60 new shots to raise the stakes. "It was recognized early enough to make the adjustment," Chu explains. "We utilized the Lidar set of the Japanese Garden, which was shot in LA and we used our own [Imocap] system to postvis the end battle. We had gotten a previs movie from everyone down south (Genndy Tartakovsky designed the Stark Expo chase sequence and prevised the original version of the Japanese Garden battle) and utilized background plates, virtual cameras and used our animators as Imocap standins for Iron Man, War Machine and Whiplash. This enabled us to feel part of the choreography."

Again, this was another instance of ILM's creative input and keeping it real world with director Favreau's demands. And look for the new lighting toolset to be used from here on out at the studio.

Bill Desowitz is senior editor of AWN & VFXWorld.