User Guide

397
ADOBE AFTER EFFECTS 5.0
User Guide
Track point Move the cross hair to specify the point of attachment between the tracked
area and the second layer. The Tracker/Stabilizer generates keyframes for the specified
track point and copies them to the position property of the second layer; when you play back
the layers, the second layer is attached to the track point of the first. If you are stabilizing a
layer, the Tracker/Stabilizer copies the tracking data to the stabilized layer’s anchor point. If
you are attaching an effect instead of a second layer, the Tracker/Stabilizer copies the
keyframes to the specified effect point. You can place this effect point anywhere in the image.
The cross hair is not visible when the tracker is in stabilize mode, because the track point is
always the center of the feature region.
To move the search region, feature region, and track point all at once, drag between the
handles of the feature region. To move the feature region without moving the track point,
Alt-drag (Windows) or Option-drag (Mac OS) the feature region.
Defining tracking settings
Use the Options dialog box, available from the Tracker/Stabilizer Controls, to specify the
second layer or the effect, and to define other tracking settings. The controls are as follows:
Layer menu Specifies the layer you want to attach to the tracked layer.
Effect Point Control menu Specifies an effect to attach to the track point. Note that you
can attach only those effects that have position properties.
Frames per Second Specifies a frame rate for tracking. In general, the tracking frame rate
should match the frame rate of the footage, which should match the composition’s
frame rate.
If you are attaching a motion graphic to the tracked area, be sure to match the frame rates
of the two layers.
Track Fields Tracks the motion in both video fields of interlaced video. The Track Fields
option doubles the frame rate to ensure that both video fields are tracked.
Track in Reverse Tracks backward in time. For example, if you are tracking an object that
comes in from off-screen, you can define your tracking regions at the end of the clip and
then track backward in time.
Use Specifies the type of comparison method to use for tracking an object in subsequent
frames. RGB bases tracking on all three color channels. Luminance compares the contrast
in brightness values in the tracking region. Saturation looks at how much color is present
in the tracking region.
UG.book Page 397 Wednesday, February 21, 2001 12:05 PM