Apple Motion 5.1.1 - Manual (Page 988)

Chapter 22 Motion tracking 988
Note: Keyframes cannot be created for automatically stabilized footage. Use the Track Region
option for adjusting automatic stabilization, or convert the stabilized footage to keyframes. For
more information on the Track Region parameter, see
Stabilize workflow on page 971. For more
information on converting tracking data to keyframes, see “Convert tracks to keyframes” above.
4 Navigate to the next frame where you want to create a keyframe.
Repeat steps 2–4 until you’ve completed the track.
5 In the Behaviors Inspector, click the disclosure triangle for the track you have adjusted, then
choose Use Existing Keyframes from the Fail Behavior pop-up menu.
6 Go to the first frame of the clip, then click the Analyze button in the behavior HUD or Inspector.
Note: You can also use the Tracker Preview in the Behaviors Inspector to reposition trackers in
the Canvas.
Important: Even though keyframes are created, you must analyze the footage to obtain the
tracking data.
Track perspective, scale, or rotational shifts
For images with significant change in size and angle, you can try a few different strategies.
Use a larger search area
m In the Behaviors Inspector, click the track’s disclosure triangle to display the Search Size
parameter, then increase the value.
Lower the Fail Tolerance value
m In the Behaviors Inspector, click the track’s disclosure triangle to display the Fail Tolerance
parameter, then decrease the value. With a lower Fail Tolerance value, the tracker is more likely to
find a false match. With a higher value, the tracker is more strict in finding a match.
Begin the analysis at the clip’s midpoint
m Move the playhead to midpoint frame of the clip and track forward to the end frame of the clip,
then return to the midpoint frame and track backward to the beginning of the clip.
Track obscured or off-frame points
In addition to experimenting with tracker parameter settings, there is a basic technique to
correct track points that become obscured by moving offscreen or by an object passing in front
of them.
The following sequence is a simple example of a candidate for offset tracking. As the car moves
forward, it passes a tree that temporarily obstructs the reference pattern.
When the reference pattern becomes obscured, the Offset Track checkbox lets you move the
tracker, picking a new reference pattern in a different area from the original reference pattern.
The offset between the original reference pattern and the new pattern is calculated to maintain
continuity in the resulting track path.
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