5

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 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, or confidence
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. After 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: 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 existing keyframes. Use this option if you
manually create track position keyframes to guide the tracker. After manually adding
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.
1349Chapter 22 Motion Tracking