Non-Linear Animation: Animating with the Trax Editor in Maya 4.5 and 5

By Brian J. Immel

This tutorial assumes that the user has knowledge of Maya's interface and how to create keyframe animation on both character rigs and simple objects. This tutorial will cover or touch all aspects of Maya's Trax Editor and various techniques used to create non-linear animation.

Disclaimer: The information covered here works for Maya version 4.5 and 5.0. There are significant upgrades to Maya’s Trax Editor in version 6.

To see the reference image, click on the linked figure number. To return to your previous instruction line, click on the figure image.

 

What is Non-Linear Animation?	Why use NLA	When not to use NLA	Build your animation first
Converting keyframes into Poses and Clips in the Trax Editor	Using the Poses and Clips in the Trax Editor	Modifying Clips	Layers of NLA
Advance NLA	The Big Show: Recreating a Slow Motion-Hyper Fast Animation Sequence	References and Resources

What is Non-Linear Animation?

Non-linear animation is a technique used to re-use linear animation for retiming, looping and other animation effects.

Why use Non-Linear Animation

1. To simplify the animator’s job for long-term projects,
2. To create special effects using motions (over used example: Matrix’s Bullet Time effect),
3. Can be used as another tool for creating complete animations.

When not to use Non-Linear Animation

If the animation cycle(s) were short and used just once, it would not be in your better interests to spend the time to set up the NLA. You should only use NLA techniques if the motions you are planning to build and use will be repeated in your current project or they can be adapted to future projects.

Build Your Animation First

1. Planning your animation

• Once you have decided what animation you will be using, you need to make sure the animation that you will use can be looped or blended from one cycle to the next.

2. Planning the animation cycles

• As you build you animation cycles, keep in mind that the cycles need to loop well if you plan on using repetitively.
• “How long should my cycle be?”
  • As long as it needs to be. A cycle that is very short (lets say 6-30 frames) repeats very quickly. After a while, the viewer will start seeing the (re)cycling of animation and get bored with it. If you make the cycle too long (more than 20 seconds) then the data used to make that cycle may be inefficient use of memory and should be breakdown down into small cycles. A good animator knows to break up the cycle a little bit to keep the animation from getting boring. A good example to making a walk cycle more interesting would be adding a little skip or hop somewhere in the middle of the cycle. Using NLA techniques, this can be very easy to accomplish.

3. Making a clean cycle

• To start with, your cycle should start and end on the same stance or pose. However, if you stop here, your cycle will have a short hesitation because the first and last frames are exactly the same. To correct that, insert a new key a frame or two just before the last keyframe and delete the last keyframe.

4. Return stances

• What is a return stance or neutral stance
  1. In gaming, a return stance is a pose the character assumes when he/she is not in motion. Usually, the pose is very neutral in positioning the legs, arms, hands and head.
  2. More often than not, this neutral pose is standing upright. The arms are comfortably at your side. Your legs are placed next to each other and neither one is ahead of the other. The hands return to the previous state (whether that was holding a weapon, making a fist or being in a slightly closed position). The head should return to looking forward and the chin level to the shoulders.