Computer Graphics World

July 2009 26 n n n n CG Characters crew in postproduction tear the trees apart from limb to limb. "When you have giant robots fighting in a forest in a Michael Bay movie, you're going to be breaking trees," Smith says. To break the trees as the ro- bots crashed into them, technical directors strung rigid-body objects together with springs so the objects would have mass and weight, and could collide and bend like a tree branch. To splinter a tree, the TDs used springs that snapped when hit hard enough. "We could tune the stiffness and mass on the springs," Smith says. e idea is akin to that of the TDs at Pixar who used strings of rigid bodies to capture Kevin in a net in Up (see "e Shape of Animation," June 2009); similarly, the ILM TDs creat- ed a net that holds two Transformers down until one slices through it with a sword. To help the animators, look developers, and TDs work with the giant robots, ILM created a multi-res pipeline that would au- tomatically look at the shape of individual parts and change the amount of detail in the geometry—the resolution—for some more than others. Because the creation of this ge- ometry at different resolutions was procedur- al, modelers didn't have to create parts with various levels of detail. All told, the animators could choose any of seven resolutions, from "pawn" resolution, which was handy for the rigid-body simulations, to 1300k. "We could block a shot with a light version of a character and as the shot pro- gressed, incrementally increase the level of detail," Benza says. Fifty animators worked on the film, more than twice the number who animated the robots in the previous release. As before, they used a dynamic rig- ging system that allowed them to group parts together on the fly. Any part, even on the Devastator, could move. Although the animators created most of the action with keyframing, to help give the robots a little extra reality, procedural animation and simulations helped them sweat, cry, spark, drip, release gas, and squirt their version of blood when injured. "We used anything we could to make them look like what would happen if hoses were cut and wiring was chopped on a physical machine," says Farrar. Damage Control All that fighting, chopping, and cutting cre- ated surface damage, as well, and that creat- ed extra work for the modeling and painting crews. "One of the things I'm most proud of is the damage on Optimus Prime," says Fogler. "He gets covered with dirt, gouges, and scrapes, and one thing that intimidates me most is bending metal. Most of the tools we have to bend polygonal meshes are for creatures, and they're great for creat- ing a knuckle. But a dent in a car door has a specific shape, with a soft area and sharp corners, and unless you model that specific shape, it doesn't look real." Aaron Wilson, the artist assigned to Op- timus, created close to 90 percent of the damage with textures. "It's surprising how much you can do in texture, especially us- ing ZBrush as a displacement tool," Fogler says, referring to the Pixologic product. "We added the damage to the robots as shapes in order to bend and distort pieces of metal, and had an additional texture flag. A TD could load levels of damage." Wilson, for example, developed a routine for adding texture to Optimus depending on the damage. "He even had clumps of dirt and grass, as if he had fallen into the sod like a football player," Fogler says. roughout the process, ILM's role was more of a collaborator than a service bu- reau. e ability of the studio's digimatte department to replicate locations digitally gave Michael Bay camera moves he other- wise couldn't do or might think of later, and for all the CG scenes, the studio put a virtual camera into Bay's hands on a mo- tion-capture stage so that he could frame shots of CG actors in the same way he might frame shots of actors on location. e ILM artists also looked for other ways to bring Bay's style to their shots. In an all-CG scene that takes place on an- other planet, Megatron visits the Fallen, who, we learn, provide energy for newborn Decepticons. "We loaded the environment with dust, drips, goo, and mist," describes White. "We had drifting stuff, droplets falling onto the ground. We were thinking about how Michael would make this an in- teresting environment for the characters." ey even added "edge corners," which are artifacts of 35mm film, to create the illu- sion that they filmed the characters on a real set. Similarly, for the all-CG underwa- ter shots, they used an Apple Shake plug-in developed by Horvath that replicates light transmission underwater, and then added dust and swirling elements in the comp to mimic reality. In this sequence, which The Doctor Bot, which transforms from a microscope, is the smallest robot that ILM created, but the smallest 'bots in the film are the Microcons created by Digital Domain.

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