Apple Motion 4 - Manual (Page 1294)

Note: The maximum default for the Look Ahead Frames slider is 10 frames. However, you
can enter a larger frame amount using the adjacent value slider.
4 While holding down the Command key, click the tracker in the Canvas, then drag in the
direction the reference pattern is moving in the clip.
As you Command-drag the track point, an inset displays a magnified view of the frame
specified in the Look Ahead Frames parameter.
5 When the look-ahead tracker is positioned on the reference pattern, release the mouse
button.
When you click the Analyze button, the new reference point is used as the tracking pattern.
Note: Look Ahead Frames can be used when tracking in reverse. When the Reverse
checkbox is selected in the tracking behavior’s parameters and you use the Look Ahead
Frames parameter, you are looking at previous frames rather than future frames. The
Reverse checkbox is only available for the Analyze Motion, Track (in the Parameter
behaviors category), and Track Points (in the Shapes behaviors category) behaviors.
Manually Coaxing Your Track
When dealing with more challenging tracks, you can manually insert track position
keyframes to help guide the tracker towards a reference pattern. For example, if you have
a footage with significant motion blur or objects that partially obscure the tracking pattern,
you can manually create tracker position keyframes to help guide the tracker.
To manually coax a track using the Record button
1 Apply a Motion Tracking behavior to the clip, then enable Record (press A).
2 In the Canvas, position the tracker at the reference point you want to track.
A track position keyframe is created in the behavior (visible in the Keyframe Editor).
3 Navigate to the next frame at which you want to create a keyframe.
Note: You can press Shift-Right Arrow key to jump forward 10 frames, or press Shift-Left
Arrow key to jump backward 10 frames.
4 In the Canvas, position the tracker at the reference point you want to track.
5 Repeat steps 3 and 4 until you’ve completed the track.
1294 Chapter 19 Motion Tracking