To animate a character believably, seasoned animators act out their shots and use reference material to observe timing and weight. They can then apply those observations when ani-mating a character. Just as video reference and mirrors are useful to animators, mocap can be a good reference.
At times, the motion capture is near perfect, and with just a minor cleaning, the shot's complete. At other times, you need to significantly change the shot. You might need to solve technical problems with the data , or you might need to slightly alter the character's behav-ior, which ends up requiring extensive hand keyframing. Even in these cases, the mocap can be useful as a reference for timing.
The strength of motion capture is its ability to record fine details of motion. Most opti-cal systems record markers on a sub-millimeter level, allowing for an extremely high fidelity of subtlety and nuance in your animation. Mocap has been used extensively in the past for shots that include fighting, running, stunts, and other broad-motion actions; however, with the capability to capture the slightest movement, this technology enhances effects shots that require a heightened sense of reality.
The decision about whether to use mocap straight out of the box, meaning using the cap-tured motion without changing it, often depends on the circumstances surrounding the shot.
Using Mocap for Reference
Studios such as ILM have used motion capture for character reference, as have animators at Square USA, Digital Domain, and other studios. Digital Domain's use was most apparent in
Using Motion Capture as Reference or Straight Out of the Box 89
James Cameron's film, Titanic. Titanic was a significant film, especially in the computer graphics industry, for its visual effects. Some of those effects were produced by animating human characters through the use of keyframing, motion capture, and at times a combina-tion of mocap and keyframing. Mocap was used mainly in two ways. For normal accombina-tions, such as people walking around on the deck, it was often used directly. It was used as refer-ence for some of the stunt work such as characters climbing on the railings.
What About Rotocapture?
Rotocapture is a term that was coined to describe an early technique for combining mocap reference and keyframe animation. Mocap was used as a reference, and the animation model was "rotoed," or posed into position over it.
Rotoscoping and Motion Capture as Reference?
The theory of using mocap as reference is similar to using live-action reference footage when ani-mating humans and animals. This concept is covered well in the classic animation reference, The Illusion of Life, by Frank Thomas and Ollie Johnston. This book chronicles the development of Disney animation, is a valuable resource for animators, and is an excellent addition to any animator's library. The Illusion of Life has been out of print for a while, but with luck, you can probably find it for sale online and through used book stores. Chapter 13, "The Uses of Live Action in Drawing Humans and Animals," covers how to use reference material. The authors stress several concepts, including how important it Is to use reference footage as a guide, but not necessarily directly as the animation. They also describe how helpful the footage can be when you are studying and perfecting certain actions.The development of Disney's Snow White was helped a great deal by animators who had the opportunity to study human motion through rotoscoping. Debate continues to this day as to whether or just how much of Snow White's motion was handled with this technique.
The Seven Dwarfs were animated traditionally, and live-action film was used as resource material.
It helped in developing character gestures and attitudes, as well as in examining the intricacies of a human being's actions. You can learn a lot about the subtleties of movement by examining live-action footage in detail. Motion capture can be equally helpful when approached with the same mindset.
Rotocapture and rotoscoping are similar techniques in that they both require an artist to animate on top of existing reference material. The main difference is that in rotoscoping the artist animates over a 2D plate or image, and in rotocapture the artist animates over 3D motion data. The limitation of rotoscoping is that you have only one perspective to use as ref-erence, whereas with rotocapture you can move the camera virtually anywhere in 3D space.
Animators have encountered two problems with rotoscoping: it can be extremely time-consuming, and it can be creatively frustrating. In 3D animation especially, rotocapture is becoming more antiquated with the advancement of motion capture technologies and ani-mation pipelines. These improvements let you use motion capture as a basis for your anima-tion. In essence, mocap delivers the basic elements of weight and timing with a foundation grounded in real-world physics. You can layer keys on top of motion capture data and add layers of more creative and thoughtful elements to the character's performance. You can also use the raw mocap as reference for timing in animating characters, while preserving the abil-ity to keep more creative control over the process.
Motion Capture and Final Fantasy: The Spirits Within
Hironobu Sakaguchi, the director of Final Fantasy: The Spirits Within, believed his vision could only be told through realistic human digital animation. The story required that the emotional range of the characters be genuinely human, breaking away from animation's tra-dition of exaggerating character actions. Early in preproduction, we decided that motion capture would play a central role in creating realistic digital humans, but we were also dedi-cated to the skills of the animators and wanted to ensure that the animation department was as actively challenged as the motion capture department.
The big hurdle we faced early on was: what would we keyframe and what would we capture? This question was answered in two ways. First, we decided to use mocap for human body skeletal movement, as seen in Figure 4.1, but for the complex facial expres-sions, mocap could not equal the quality of the performances that the animators created.
All animation for Final Fantasy: The Spirits Within needed to be completed wlthin just over a year and half, and that goal was met. Production for the entire movie,
however, spanned approximately four years.
Second, we decided to ensure that the animation department had the necessary tools to animate over the motion capture, in order to tweak it as a whole or in parts. Square USA developed a pipeline to ensure that the animation and mocap departments could work together. Square USA created a proprietary toolset in Maya that allowed a "hybrid" motion capture and keyframe animation process. Using the methodology of a motion-animation pipeline that supported a workflow of motion capture and animators working together, we were able to decide on a per shot level how much mocap to use straight out of the box and how much to animate over or replace completely. It wasn't always one or the other—all mocap or none. For the humans, most of the time it was a blend. For example, we might tweak some parts of the body for certain shots. Aki's hips might need more rotation, or parts of the body, such as the arms, might be keyed, and others, such as the legs, might be
mocapped. Sometimes we combined keyframe animation with mocap to accommodate a change in a character's action.