Apple Motion 4 - Manual (Page 1312)

When the Match Move behavior references another behavior, such as Analyze Motion,
the Anchor tracker becomes the Anchor pop-up menu. Likewise, the Rotation-Scale tracker
(if there is one) becomes the Rotation-Scale pop-up menu.
Click the Anchor or Rotation-Scale disclosure triangles to reveal additional parameters:
• Position: Displays the X and Y positions of the tracker. The X position is the value slider
on the left; the Y position is the value slider on the right. Click the disclosure triangle
to display labeled position value sliders.
• Track Size: Use this slider to adjust (in pixels) the pattern search size for the tracker. As
you adjust the track size, the Tracker Preview is updated to show the new track size
(there is no visual change in the Canvas tracker).
To adjust the Track Size without exposing its parameters, Option–drag left in the Tracker
Preview area to reduce the track size; Option–drag right to increase the track size.
• Search Size: Use this slider or value slider to increase or reduce the tracker’s search area
size. In Motion, you do not specify the size of a search area when setting up your trackers
in the Canvas. To change the default search size, use the slider or value slider. If Search
Size is set to 200 percent, the tracker’s search area is twice the default search area size.
• Fail Tolerance: This parameter defines the amount of tolerance for error, orconfidence
value, of the track. In other words, it defines at what “score” the tracker determines it
is able to match a reference feature. When above the score, the tracker accepts the
match. When below the score, the tracker rejects the match. Once the match is rejected,
the Fail Behavior kicks in.
• Fail Behavior: This pop-up menu specifies what happens if the track confidence value
falls below the Fail Tolerance amount. The following options are available:
• Smart Retry: The tracker attempts to find the reference pattern in a larger search area.
If the pattern cannot be found, the tracker switches to the Predict option. Smart Retry
is the default fail behavior.
• Stop: Stops the analysis when the tracker loses the reference pattern. You can also
click the Stop button in the tracking progress dialog or press Esc to stop an analysis.
• Predict: The tracker predicts a new search area without creating keyframes until it
finds a match for the reference pattern. This is excellent for tracked objects that pass
behind foreground objects.
• Predict and Key: If a failure is detected, the tracker predicts the location of the keyframe
based on a vector of the last two keyframes, and continues tracking in the new area.
• Don’t Predict: The tracker remains in its position and searches for subsequent matches
as the clip’s frames progress. While searching for a match, the tracker does not create
keyframes.
1312 Chapter 19 Motion Tracking