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Non-Linear Animation in Production
Non-Linear Animation in Production
sdb1987, added 2005-09-25 00:52:42 UTC 57,296 views  Rating:
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Adam Martinez

Technical Director, GLC Productions

Who are you and what is this?

Hello! My name is Adam Martinez, and I am a technical director at GLC Productions in New York City (www.glc.com.) As a technical director, I get asked to do all sorts of silly things, like light shots, shade models, create effects and offer emotional support to animators. GLC Productions is a computer graphics and sound design facility in the chic West Village, Manhattan. The focus of GLC for the past three years has been the development of it's flagship property The Buddy System, created entirely in Alias|Wavefront�s Maya. The pilot episode of The Buddy System, "It�s A Comic Strip," recently won first in it�s category at the Annecy `99 animation festival (where it was called Le Buddy Systeme, heh). That�s it for the plugs, I promise.

This is a discussion and case study of how one company uses the concepts and techniques of Non-Linear Animation in a television production environment. This document is by no means a programmer�s technical specification, nor do I claim to be an expert on animation tools. There is some MEL code in this document (yay!) however, I cannot be held responsible for the use or misuse of it (boo!). The MEL in this document has been written on and tested for Maya 2.0 complete on SGI workstations. Just to clarify, I did not invent, coin-the-terms, and in no way am I responsible for the headaches and heart aches associated with non-linear animation. So if your spouse leaves you because you�ve been too busy messing about with all of this silly animation stuff, don�t come crying to me, because honestly, it�s happened to me and you probably deserve whatever you get. I hope this counts as a legal disclaimer because I�m moving on now.

What is NLA and why is it following me?

Non-Linear Animation (NLA) is quickly becoming, if it is not already, the latest animation industry buzzword. While the concept, and many implementations of various complexity, have been around for a number of years, only recently have vendors and animators been focusing on NLA as a serious production tool.

Essentially, non-linear animation is a method of placing and manipulating animation from separate sources. The "non-linear" in NLA comes from the film/video editing world. Packages such as Avid MediaComposer and Adobe Premiere are examples of Non-Linear Editors; they allow easy ways to edit, blend and reposition clips of footage together on a timeline. Substitute footage with animation, and you have NLA: a way to edit, blend and reposition clips of animation (a walk cycle, run, or other behaviors) from separate sources.

What do you mean by "animation clips from separate sources"?

The concept of animation clips necessarily arises from the basis that NLA is used to blend and transition between pieces of animation. These pieces ("clips") exist independently of the scene file and the timeline of the particular shot being edited, that is, animation clips can be created traditionally or brought in from external files. For example, you�re working on a character that must use a motion-capture running sequence, but in the middle of the motion capture, you have to manually keyframe a particular motion, like a jump. Using a non-linear approach, the animator would manually keyframe the jump, without the mo-cap, and define that sequence as an animation clip. Using a NLA editor, the animator would then bring in the mo-cap as one clip, and the keyframed sequence as another clip, and do a blend, similar to a visual dissolve to and from the jump in the middle of the mo-cap. Mo-cap, keyframe and procedural animation are all examples of separate sources of animation.

How to solve all the world�s problems with a single MEL script: A case study of NLA in production.

How can we make effective use of NLA in production? The big question. At GLC productions we have been working on an episodic animation project that, from the nature of the format, requires consistent character behavior. We average 6 main characters in any given episode, two of which are the actual stars of the show, and appear in every episode. As an aide to ensure the consistency of a character�s behavior from shot to shot, and episode to episode, we considered a way of re-using animation from older shots and manipulating it to conform with a current shots requirements. What we did not want to do was actually re-use an entire shot�s worth of animation, but only bits a pieces of it that were repetitive characteristics of the character. The original idea was to create an animation library for each character, where we would store animation clips for a character and load them in when we needed them. But what we needed to do was come up with a system where we could

effectively shift those clips around in a non-destructive way. We therefore implemented a type of Non-Linear Animation editor we call the Layered Animation System (LAS).

The LAS is essentially an NLA editor and it is an extension to a large number of tools we have developed in house, both scripts and binaries, to streamline production workflow. Since our system uses a layered paradigm, much like modern compositing applications, our interface is modeled after an audio mixing board, where we can essentially mix channels of animation. You�ll notice in the screenshot above that there are other similarities to a mixing board as well, like the solo button, which is used to isolate a single track of animation.

This interface also acts as a window into our animation library, where clips of animation are stored and categorized. The library is accessed through the buttons on the lower-right corner, and the user is then prompted on which layer the clip is to be loaded. Animation is then manipulated and shifted using Maya�s internal graph editor.

The LAS allows us to maintain a consistent look and feel to the characters in our animations by enabling our animators to build on top of approved characteristics and habits. In addition, it allows animators to re-use clips of animation that they particularly like, sparing them the agony of having to re-keyframe that complicated thumb-twiddle that Howie did in "The Third Ticket." Click here to see a sample of two clips being blended together (quicktime in .zip, 1.37MB). This clip demonstrates the results of partial blending of animation curves. The arms and head of the character use the scratch sequence, while the torso and legs use the walk sequence.