Computer Graphics World

January 2009 10 ■ ■ ■ ■ CG Character 10 Creating the System In addition to tools and techniques devel- oped specifi cally to create Benjamin Button, which Digital Domain calls the "emotion system," the studio leveraged recently devel- oped off erings from Mova, Image Metrics, and the Institute for Creative Technologies, and relied on such standard commercial software programs as Autodesk's Maya and Nvidia's Mental Ray, as well as its own 3D compositing software, Nuke (now sold by the Foundry), and its Academy Award-win- ning tracking software, Track. But, it took the crew's painstaking artistry to bring the digital human to life. "[ e project] scared people at fi rst," says visual eff ects supervisor Eric Barba. "It was diffi cult to staff . People were afraid we were setting ourselves up to fail." e supervisors even had a hard time hiring from outside the studio. "I inter- viewed people at SIGGRAPH," says char- acter super visor Steve Preeg. "Every person I hired except for one opted to work on other shows. And, that person left after one day." Eventually, Barba and Preeg structured a team that was passionate about the project. "Once we started putting out renders, peo- ple were knocking down our doors," Barba says. "But, by then, we had a smooth-run- ning show. at ship had sailed." At the peak of the project, 155 artists worked on the fi lm, with most spend- ing a year and a half creating and refi ning shots, some of which took more than 100 iterations to nail down. "It was incredibly daunting," Barba says. "We had to break it into bite-size chunks so the artists' heads wouldn't explode. It's a testament to the team, that they continually knocked down challenges and were undeterred from the task at hand." Preeg jumps in with a laugh, saying, "I was deterred." Expressions Fincher commissioned the fi rst proof-of- concept tests in 2004, but research had begun at Digital Domain in 2002. Once preproduction on this fi lm began, the stu- dio started the process of replicating Pitt's expressions by painting his face green using the special makeup devised by Mova for its Contour system. For two days, one before principal photography and one after, Pitt bit his lips, puff ed his cheeks, looked up, down, right, left, raised an eyebrow, tight- ened his neck muscles, showed surprise, fear, anger, and so forth, while Mova cap- tured these expressions at 24 frames per second using 28 camera. "We walked Brad [Pitt] through a FACS session, where we recorded his face doing as many of the individual motions as he could," says Preeg. FACS, developed by Paul Eck- man and Wallace Friesen (and later refi ned by Joseph Hager), categorizes the anatomical form of emotions that play across a person's face; that is, which muscles move to create particular expressions. Mova translated Pitt's expressions into useful data that the com- pany sent to Digital Domain in the form of digital meshes. ere, the artists applied data from the meshes to the animation rigs. First, though, they stabilized the meshes. e crew wanted to encode the individual shapes within a keyframable rig so that ani- mators could tweak the expressions. But, when Pitt raised an eyebrow, he might also have tilted or turned his head, so they had to remove the head tilts and turns before they could apply the eyebrow motion to the rig. To do that, they needed to align the captured motion in all the Contour mesh frames with a neutral pose and lock the mo- tion to that pose. "We had to know from a neutral pose what raising his left brow changed on his face," Preeg says. Figuring out how to lock the individual frames to a reference pose fell to Digital Domain's award-winning creative director of software, Doug Roble. " e head motion had to be removed from the motion-cap- tured data, but all we had to work with was the data captured on his face," says Roble. Roble found technical papers that de- scribed ways of aligning models, but they didn't assume that the models changed when the subject lifted an eyebrow. He had to align models that changed over time. " e face was always moving and deform- (Left to right) Digital Domain videotaped Brad Pitt perform- ing a scene on a soundstage. Later, the studio applied Pitt's performance to a CG model of Benjamin. (Top) A body double wearing tracking dots plays Benjamin Button during principal photography for that scene. (Bottom) The fi nal shot in the movie.

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