Animation Artist

Motion Capture vs. Keyframing

Mainframe Entertainment runs daily mo-cap sessions (top) to produce character animation for shows like "Action Man" (center) and "Heavy Gear".

For humanoid characters, the debate over motion capture rages on. The industry largely seems to be splitting along TV-film lines-heavy use of motion capture for TV animation, general reliance on keyframe for feature films.

Indeed, most completely CG television shows have, by now, turned to mo-cap. Even Mainframe Entertainment, Vancouver-the company that pioneered production of all-CG children's programming using meticulous keyframe methods-has joined the mo-cap world. Last year, Mainframe purchased a Motion Analysis, real-time, optical system and promptly moved into production on two, new series, "Action Man" and "Heavy Gear", as well as an upcoming "Reboot" TV movie.

"We still primarily depend on keyframe animation for facial work," says Alastair Macleod, senior motion capture technical director at Mainframe. "But for body movement, we largely use mo-cap. The reason we did it, though, is not so much related to cost or speed. We made the move because that is what clients were requesting. Hasbro [producers of "Action Man"] felt motion-capture was established enough to give them the look they wanted, so they asked us to produce the show that way. Once we bought the rig, it made sense to use it for other projects, as well."

Macleod says that motion capture has permitted Mainframe animators to move past mundane functions to more complicated work.

"It makes sense for us to mo-cap things like basic walk cycles," he notes. "Even with a show like "Heavy Gear", we have found that we can create basic movement cycles this way, even though the characters are not human-they are giant robots. We wanted more robotic movement, obviously, but we found that by putting prosthetics on the actors on the mo-cap stage-ski boots and hockey gear-we can get robotic movement with the mo-cap system and save some time. But particularly for walking, running, and standing up, motion capture has proved useful."

Foundation Imaging, which relies on Vicon 8 optical technology, uses mo-cap mainly for children's shows. Teska suggests that the concept of building motion libraries will likely evolve into a logical next step for facilities like Foundation Imaging, which possess both sophisticated mo-cap stages and huge CG character workloads.

"We've had such a huge body of motion come through our shop, it seems obvious we could use some of that data as challenges come along," says Teska. "If you know where to look, you could probably build a huge library and use it regularly on new shows. Eventually, it would make sense to catalogue that stuff more than we do now. We have already used generic walk cycles for different projects, "Starship Troopers: Leathernecks" and "Voyager" in the same season, for instance."

Commercials are less apt to take advantage of motion capture because of short turnaround times and the need to stylize spots. Sometimes, though, mo-cap can bring unique performances to even simple, 2D animation. Late last year, Mary Kay Cosmetics hired Computer Animation Technology (CAT), Dallas, to capture dance moves from three dancers with its Vicon 8 system, not for insertion into detailed computer models, but for use with 2D brush-stroked illustrations.

"The characters were paintings, and the commercial was more of a painting with moving images," says Trent DiGiulio, president of CAT. "They wanted these little brushed stick images choreographed so they would interact in a way that would be difficult to replicate with keyframe animation, to give them human motion. This was the furthest thing possible from photo-real animation. The end result is very stylistic animation, not what you would normally associate with motion capture."

Feature filmmakers, however, usually have years to produce projects, and so, studios tend to rely on keyframe techniques. While New Line Cinema is currently permitting vendor Weta Digital of New Zealand to use mo-cap for its upcoming Lord of the Rings trilogy, and a handful of low-budget, indie films are using mo-cap tools, most big studio pictures still keyframe characters.

"For films [like Shrek], there is usually discussion and tests relating to motion capture at the start, and that is what we did. But in the end, we chose to keyframe everything," says Adamson. "I think it's a stylistic choice. For a movie like ours, and many others, you want movement to be stylized, different than real-world motion. Our lead character, Shrek, for instance, is a big green ogre, and we wanted him to move something like a lumbering, fat guy, but with a few differences. In that case, keyframing made more sense."

Final Fantasy, on the other hand, relies on both motion capture and keyframing for its characters. The decision about which approach to take for which shots depends, Jones says, on the movement in question.

"We mainly use motion capture for larger, quicker actions, a lot of action sequences with running, fast walking, jumping, and so on," explains Jones. "For subtle movements, close-ups, facial work, basic joint movements in the hands or feet, we keyframe. The goal is to make seamless transitions between those shots."

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