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Nonlinear Animation

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One of the biggest recent advances in animation is nonlinear animation (NLA), which allows animators to think and create above the level of the keyframe. George Maestri looks at the nuances of NLA in this article.
George Maestri is the author of several animation books from New Riders Publishing, including [Digital] Character Animation 2, Volume I and [Digital] Character Animation 2, Volume II. He is also the series editor for New Riders' [Digital] series of books, including [Digital] Lighting and Rendering and [Digital] Texturing and Painting.
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Nonlinear Animation

For the past 20 years, digital animators have pretty much created animation the same way—a keyframe at a time. Sure, animators can do stuff that traditional animators can't do, such as manipulate keys to fine-tune an animation, as well cut and paste keyframes to transfer animation from one character to another. However, these are simply variations on a theme.

In the past few years, software has finally given animators another option. Nonlinear animation (NLA) is one of the biggest advances in animation in a long time. NLAs allow the animator to think and create above the level of the keyframe. Many vendors, such as Softimage, Alias Wavefront, and Nichimen, offer these solutions (see Figure 1). A good NLA allows the animator to edit motions as a whole, not just the individual keys. Nonlinear animation is not just about editing and manipulating groups of keyframes, but it also allows you to combine, mix, and blend motions to create entirely new animations. This is similar to how nonlinear video editors, such as Avid and Premiere, work.

Figure 1 A nonlinear editor looks much like a video-editing application.

Another analogy would be in the world of audio. The phenomena of remixing is very similar to NLAs. Although these techniques had been around since audiotape, when computers became fast enough to handle audio with ease, producers and composers started using digital tools much more frequently. Computers allowed musicians to slice and dice existing music with incredible ease, giving them a whole new way to make music. Nonlinear animation offers many of the same opportunities for animators.

The bottom line with remixing, however, is that you still need good source music to get a great result. The same goes for NLAs. If the underlying motions are good, then the results will be good, too.

Creating Motion Primitives

With that in mind, the best way to animate for a nonlinear system is to create well-animated motion primitives. These are the basic building blocks from which you will create more complex motion. These can include such motions as standing around, a basic walk and run, and so on (see Figure 2). You may also need other types of bridging motions. In many ways, the library of motions is very much like the one you need when animating for games (see one of my previous articles "Animation for Games").

Figure 2 A library of motions is a good idea when working with an NLA—here we have stand, walk, run, and sneak.

Determining which motions you'll need is half the trick. In a larger-scale production, such as a series or a feature, you'll probably want to animate a large library of motions. For a shorter project, such as a commercial, you don't want to waste time animating motions that you're never going to use.

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