Chapter8.Effective Motion Tracking

Chapter 8. Effective Motion Tracking

Image courtesy of Tim Fink Productions.

Even if you're on the right track, you'll get run over if you just sit there.

Will Rogers

The After Effects tracker is a semi-automated solution for two-dimensional match moving and stabilization. Set up correctly, it allows you to click a button and get a result more refined than anything you could ever animate by hand. It can save you piles of time, too, such as the several months I spent hand match moving shots for Rebel Assault II using After Effects 2.0, which had no motion tracker whatsoever. It wasn't added until version 4.0, allowing me to learn everything I know about keyframes. But, having the tracker doesn't mean you get to click a button and put your feet up on the desk, George Jetson style.

First, you need to make sure you're using the tracker to best effect. Some of the most common ways people go wrong are

• Failing to choose good track points

• Misunderstanding how the tracker does its job, and not knowing when to change the default settings

• Giving up on tracks that seem to have gone wrong (although abandoning them is a good idea once you understand what may have gone wrong)

• Forgetting about motion blur

• Failing to realize all the different ways tracking data can be applied

This chapter will help you with all of the above and much more.

Once you've nailed down these essential techniques, you can move on to some elegant uses of the tracker, including

• Using the After Effects 3D camera as if it were a physical camera, matching objects you insert in the scene to the scene motion automatically

• Procedurally smoothing a camera move (as opposed to simply stabilizing a static shot)

• Using a simple expression to continue tracking an object that has moved offscreen

  

  The tracker is available only in After Effects Professional. If you are using After Effects Standard, skip ahead to the final section of this chapter, which focuses on importing 3D match moves from third-party software.

  
  

• Giving your effects three-dimensional depth even though After Effects does not support 3D objects

Don't forget, the tracker's uses go beyond those clearly spelled out in the Tracker Controls palette (which can always be revealed by choosing it in the Window menu, although it appears automatically upon applying a track).