Point Tracking Essentials

Point Tracking Essentials

Step one is to be able to get a good basic track right in
After Effects. You may fi nd your tracks going astray after
reviewing the clear After Effects documentation on how to
use the tracker. Here are some background fundamentals.
Tracking is a two-step process: The tracker analyzes the
clip and stores its analysis as a set of layer properties that
don’t actually do anything. The properties must be applied
to take effect. Both steps, setting the tracking target and
applying the track, occur in the Tracker Controls panel
when matching or stabilizing motion in After Effects.
Choose a Feature
Success with the After Effects tracker relies on your ability
to choose a feature that will track effectively

Ideally, the feature you plan to track
. Is unique from its surroundings
. Has high-contrast edges—typically a corner or point—
entirely within the feature region
. Is identifi able throughout the shot
. Does not have to compete with similar distinct features
within the search region at any point during the track
. Is close to the area where the tracked object or objects
will be added

The main decisions when setting up a track regard the size
and shape of the Search and Feature regions. Keep the following
in mind:
. A large Feature region averages pixel data, producing a
smoother but possibly less accurate track.
. A small Feature region may pick up noise and grain as
much as trackable detail, creating an accurate but jittery
track.
. The bigger the Search region, the slower the track.
. The Feature region doesn’t have to contain the area of
frame you want to match. One way to offset a track is to
move the attach point—that little x at the center of the
tracker. A better solution is to apply the track to a null,
as is discussed later.
Most features that you’ll track are unreliable—they change
perspective, lighting or color throughout the course of the
shot. The following sections explain what to do when you
don’t have a constant, trackable feature exactly where you
want your target to go.