5

Click the disclosure triangle next to the track name 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: Use this parameter to define the amount of tolerance for error, or
confidence value, of the track. In other words, this parameter 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. When
the match is rejected, the Fail Behavior kicks in.
Fail Behavior: Use this pop-up menu to specify 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: The analysis stops 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.
• Use Existing Keyframes: The tracker uses manually added keyframes as a guide during
analysis. After you add keyframes, return to the start frame and start the tracking analysis.
If the tracker cannot locate the track pattern, the manually created tracking keyframes
are referenced to guide the tracker.
1361Chapter 22 Motion Tracking