Analyze Motion Controls
The Analyze Motion behavior is designed for use with footage (a movie or image
sequence). This behavior can be thought of as a traditional correlation tracker—you
position an onscreen tracker on a reference pattern on a clip. The movement of the clip
at the specified reference point is analyzed, and the analyzed data is saved in the behavior.
The recorded data can then be applied to other objects in the project.
The Analyze Motion behavior does not transform the input image. It is used to generate
tracks that can be referenced by the Match Move, Stabilize, Track Parameter, and Track
Shape behaviors.
For information on using the Analyze Motion behavior, see
General Motion Tracking
Workflow
.
Note: Analyze Motion cannot reference other tracking behaviors.
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Important:
The Analyze Motion behavior can only be applied to footage objects (a
QuickTime movie or image sequence).
Parameters in the Inspector
Movement:
The Movement parameters contain the Analyze and Reverse controls.
• Analyze: This button, when clicked, begins the motion tracking analysis. When you
click Analyze, a status window appears and displays the tracking progress. To stop the
analysis, click the Stop button in the status window or press Esc.
The start of the track is based on the current playhead position, rather than the start
of the behavior in the Timeline.
• Reverse: This checkbox, when selected, reverses the analysis direction, going from the
playhead position to the first frame of the clip (or the first frame of the tracking
behavior).
Note: You must move the playhead to the frame where you want the reverse analysis
to begin.
Tracker:
This button lets you add trackers to the Analyze Motion behavior. By default,
one tracker is available. New trackers are added at the center of the Canvas.
Tracker Preview:
This preview area provides a magnified view of the tracking reference
area for the selected tracker. The preview updates as you adjust the position of the tracker
in the Canvas. You can drag in the preview area to adjust the position of the tracker.
When dragging in the preview area, the image moves around the red crosshair that
represent the tracker, while the tracker moves in the Canvas. You can also Option-drag
left or right to decrease or increase pattern size. (You can also adjust the Track Size slider
to achieve the same result.)
Offset Track:
This checkbox lets you select a new reference point when the original
reference point becomes temporarily hidden or goes off the screen. Motion uses the new
tracking point to continue the same tracking path as the original reference point. For
more information on offset tracking, see
Tracking Obscured or Off-Frame Points Using
Offset Tracking
.
Auto-Zoom:
This pop-up menu lets you choose a magnification level when positioning
the tracker in the Canvas. You can zoom in on the Canvas when searching for an ideal
tracking reference pattern. There are four choices: None, 2x, 4x, and 8x.
Auto-Zoom Mode:
This pop-up menu lets you set the display of the auto-zoomed tracker
in the Canvas. There are three choices:
• Normal: Displays a normal pattern.
• Contrast: Displays the tracker pattern with contrast detection.
• 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.
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Note: When None is chosen from the Auto-Zoom pop-up menu, the Auto-Zoom Mode
setting has no effect.
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
Giving Motion a Hint by Looking
Ahead
.
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 additional parameters:
• 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.
• 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.
• 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.
• 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.
• 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.
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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.
• 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 keyframes you have manually created as a
guide. After manually adding keyframes, return to the start frame and start the
tracking analysis. If the tracker has difficulty locating the track pattern, the manually
created tracking keyframes are referenced to guide the tracker.
• Color: This color control sets a new color for the onscreen tracker. The default tracker
color is red. When a tracker is selected, its center point is yellow and the border of its
magnified inset is the color set in the color well. To adjust individual color channels,
including the tracker’s opacity, click the disclosure triangle.
HUD Controls
The Analyze Motion HUD contains controls to start the motion track (the Analyze button),
reverse the direction of the track (the Reverse checkbox), and to specify an offset track
(the Offset Track checkbox). Offset tracking allows you to reposition the tracker at a new
reference pattern.