Step by Step: Transformers: Revenge of the Fallen

Ever since the success of Transformers for Paramount Pictures and director Michael Bay in 2007, expectations for the sequel have been high. With Transformers: Revenge of the Fallen, Bay has some nasty new bad guys to reveal. In one shot, tens of thousands of plague-infected ball bearings are unleashed through a ventilation system. Each one of them hatches into a tiny insect-like robot called a Microcon, and this group then assembles—en masse—into a fearsome robot that''s completely new. Creating this complex series of transformations was the assignment given to Digital Domain
(DD) in Venice, Calif.

“It''s fully synthetic. There was no background plate,” says DD Visual Effects Supervisor Matthew Butler. But because this shot had to hook up with a steadicam shot from a real set, Butler''s team surveyed that set and took digital photographs and high dynamic range images of the lighting. Armed with that material and a previz from Bay, DD set about creating a CG environment that blended seamlessly.

“Our 3D background was created in Nuke,” says DD CG Supervisor Paul Palop (referring to the software developed at Digital Domain and now sold by The Foundry). Because thousands of ball bearings were so close to the floor in this shot, Palop''s team had to pay additional attention to the way the 3D CG floor was constructed and rendered. For that, DD used Autodesk Maya
and Pixar RenderMan.

Although the shot is synthetic, Bay provided real-world references of how ball bearings should move. “Mike Bay loves the practical photographic world,” Butler says. “Since these ball bearings are supposed to fall down through air vents, Mike photographed hundreds of practical ball bearings falling and rolling around. The shot calls for these Microcons to have some self-awareness, so Mike got under a table holding large magnets and made the ball bearings move around in a staccato manner. That set the tone for our CG ball bearings. We had the advantage of knowing what they do in reality—and the disadvantages of having to replicate that.”

“I think we did 30,000 CG ball bearings,” Palop say. “We had to develop a crowd system in [Side Effects Software] Houdini to be able to control their behaviors. Houdini can assign a charge to a particle and you can set up rules that define how that charge changes over time depending on what''s happening around it. We could define, based on the reference from Michael''s photography, what these guys needed to do to make it to seem like they had some level of intellect. The approach we took was to simulate particles, give them a behavior, and stamp
prebaked animation cycles from our library onto those particles. Our system chooses—depending on the action required—which animation cycles we would stamp on the particles.”

The metamorphoses that each ball bearing undergoes as it changes from a sphere into an insect-like creature was a challenge. “It was the least mechanical transformation that we dealt with,” Palop says. “It was more of a complex organic thing. We needed to imply the unfolding shape transforming and locking into place. We did shortcuts wherever possible. Once we freed ourselves from the physics of what should happen and we started doing what needed to happen, it became an easier problem. There was no volume conservation. It was a hand animation process, and once we had an iteration that was approved, we archived the geometry and the animation data and cloned it all over the place. We did variations so it didn''t look too CG. We had a couple of main transformation cycles—for in-place guys and guys who transformed on-the-go. It was important to convey the theory that the guys were swarming and assembling.”

Depth-of-field was a huge issue, given that about 15 ‘hero'' Microcons were close to camera and seen at high resolution, while the rest needed to appear believably busy in the background. “The distinction between the foreground and background characters is pretty gray,” Butler says. “The foreground guys were hand-animated [in Maya] and placed to camera. At the same time, we had another team that was taking the animation archived on disk and applying it procedurally to the particle system setup. We couldn''t have a hard delineation between foreground and background. There had to be enough variation put in there to give the illusion that they were gravitating in a direction.”

Lighting was also a multileveled task. “We had to approach it from two different angles,” Palop says. “For the hero guys in front, we have a pipeline based in Maya and RenderMan. The background guys were rendered through [Side Effects] Mantra. We had the same artists lighting both. We had to render them with the hero guys for holdout purposes because they do overlap in the middle ground, where hero guys intermingle with little guys from the particle system.”

The HDR information that DD had collected on set was valuable. “Metallic surfaces are tricky to light because of the small diffuse component they have,” Palop says. “All the reflections that we''re seeing on these little guys have the dynamic range of true reflections because we had good HDR data. On top of that, we did a layer of CG lighting with RenderMan and Mantra.”

“We generated many layers of lighting for the compositor,” Palop says. “We didn''t render depth-of-field because it''s a lot slower process, so we pushed the difficult computations of depth-of-field to the end. Everything was rendered sharp and then treated in Nuke for the final image.”

The end result, Butler says, “Looks primal, because we are inherently creeped-out by little critters. But they still needed to look cool. What Michael Bay kept saying was: ‘Just make it look cool.''”

Director: Michael Bay
Previz: Proof

For Digital Domain:
Visual Effects Supervisor: Matthew Butler
CG Supervisor: Paul George Palop
Animation Supervisor: Dan Taylor
Compositing Supervisor: Lou Pecora
Character Set-up Lead: Richard Grandy
Character Animation Lead: Erik Gamache
Character Animator: Tim Ranck
CG Effects Animation Lead: Phillip Prahl
CG Effects Animator: Edmond Smith III
CG Modeling Lead: Melanie Okamura
CG Texture Lead: Cathy Morin
CG Lighting Lead: Charles Abou Aad
3D Integration Lead: David Niednagel
Technical Developer: Shoichi Matsubara
Compositor: R. Matt Smith