User Guide

CHAPTER 13
400
Using Property and Tracking Controls (PB only)
The rotation in the first layer is defined by two feature regions and the axis that runs
between them. An arrow on the axis points from the first feature region to the second. The
Tracker/Stabilizer tracks the rotation by measuring the angle of the axis in relation to the
first feature region: as either feature region moves, the angle of the axis changes. Note that
even if the objects tracked inside both feature regions are moving up, down, or across, the
Tracker/Stabilizer tracks only the relative rotation between the regions, not the overall
movement. Because the second layer is not attached to the first, there is no track point.
To define tracking regions for rotation:
1 Place the first feature region (on the left by default) over the object you want to specify
as the base of the axis. Rotation is measured relative to the center of this region. If the
object is moving, size the search region appropriately.
2 Place the second feature region over the object that defines the angle of rotation. Size
the search region appropriately.
Tracking position and rotation
When you track both position and rotation, you attach a layer to a single track point, so
that the attached layer not only follows the tracked region but also duplicates the rotation.
This type of tracking is useful when the feature regions contain a lot of motion. With
position and rotation, the track point is fixed in the center of the first feature region. To
adjust the position of the attached layer, adjust its anchor point after applying the tracking.
To define tracking regions for both position and rotation:
1 Size the first feature region (on the left by default) over the object you want to track.
The second layer is attached to the center of this region. This region defines the base of
the axis.
2 Size the second feature region over the object that defines the angle of rotation.
3 Size both search regions appropriately.
UG.book Page 400 Wednesday, February 21, 2001 12:05 PM