Apple Motion 5.1.1 - Manual (Page 995)

Chapter 22 Motion tracking 995
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Normal: Displays a normal pattern.
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Contrast: Displays the tracker pattern with contrast detection.
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Edge: Displays the tracker pattern with edge detection.
The Auto-Zoom Mode applies to trackers in the Canvas and does not appear in the Tracker
Preview in the Behaviors Inspector.
Note: When None is chosen from the Auto-Zoom pop-up menu, the Auto-Zoom Mode setting
has no effect.
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Look Ahead Frames: This slider and value slider allow you to specify the number of future
frames to be analyzed by the tracker. In other words, you can direct the tracker to look in a
specific location for its reference point. This is useful for footage that contains fast-moving
objects, because the reference point can quickly get away from the tracker. For more
information on using Look Ahead Frames, see
Advanced strategies to improve tracking
results on page 984.
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Track list: This list displays the trackers in the behavior. In the Analyze Motion behavior, the
trackers in this list are called Track 1, Track 2, and so on. To disable a tracker, deselect its checkbox.
To remove a tracker, click the Remove button. A tracker that is turned off is not analyzed. Click
the disclosure triangle next to the track name to reveal these additional parameters:
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Position: This parameter 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.
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Track Size: This slider adjusts (in pixels) the pattern search size for the tracker. As you adjust
the tracker size, the Tracker Preview is updated to show the new tracker 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 tracker size; Option-drag right to increase the tracker size.
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Search Size: This slider increases or reduces 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.
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Fail Tolerance: This parameter defines the amount of tolerance for error, or confidence value,
of the tracker. In other words, it defines at what score the tracker determines it can 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.
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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:
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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.
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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.
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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.
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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.
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