Track Points Controls
The Track Points behavior allows you to link the control points of a shape or mask
(including paint strokes) to reference features on a source clip. This behavior also allows
you to apply tracking data recorded by the Analyze Motion, Match Move, or Stabilize
tracking behaviors to the control points of a shape or mask.
The Track Points behavior can be found in the Behaviors’ Shape subcategory in the Library,
or by choosing Shape > Track Points from the Add Behavior pop-up menu in the toolbar.
For information on using the Track Points behavior, see
Track Points Workflow
.
Parameters in the Inspector
Source:
Use to drag a source object for the track points to this well. The source object
can be another tracking behavior, an animated object, or a footage object. To clear a
Source well, drag the item away from the well and release the mouse button.
• Action pop-up menu: Choose from a list of tracking data (from other tracking behaviors)
in the project.
Transform:
Use this pop-up menu to choose how the destination object moves. There
are two options:
• Attach to Source: This option anchors the foreground object to the recorded track or
animation source. Use Attach to Source when the source object is scaling or rotating,
and you want the destination object to “stick” to a specific spot on the source object.
Any animation that existed on the destination object before applying the track can be
preserved by using the Adjust parameters (Position, Scale, and Rotation), available
when Transformation is chosen from the Type pop-up menu.
Note: Although the destination object is attached to the movement of the source
object, the destination object can be offset from the source object.
• Mimic Source: This option allows the destination object to “mimic” the recorded track
or animation source. Any animation that existed on the foreground object before
applying the track can be added to the track by selecting Position, Rotation, or Scale
in the Adjust parameters.
Note: As with Attach to Source, the destination object can be offset from the source
object.
Align Tangents:
When this checkbox is deselected, tangents remain aligned at their
original angles. When the checkbox is selected, the tangents match the transformation
of the source animation, and the shape changes its form.
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Movement:
The Movement parameters contain the Analyze and Reverse parameters.
This parameter appears only when there is a tracking source (footage) in the source well.
• Analyze: Click the Analyze button to begin the motion tracking analysis. 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: When the Reverse checkbox is selected, the clip is analyzed from the current
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 to begin the reverse
analysis.
Tracker Preview:
This preview area appears only when there is a tracking source (footage)
in the source well. Use the preview to see 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 also drag in the preview area to adjust the position of the tracker.
When dragging in the preview area, the image moves around the red crosshairs in the
preview and the tracker moves in the Canvas.
Offset Track:
This parameter appears only when there is a tracking source (footage) in
the source well. If a tracker’s reference point becomes temporarily hidden or goes off the
screen, this parameter allows you to select a different reference point that continues 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 parameter appears only when there is a tracking source (footage) in
the source well. Choose an option from this pop-up menu to set the magnification level
when positioning the tracker in the Canvas. This allows you to 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 parameter appears only when there is a tracking source (footage)
in the source well. Choose an option from this pop-up menu to 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. 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 parameter appears only when there is a tracking source (footage)
in the source well. 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:
Tracks appear only when there is a tracking source (footage) in the source well.
The Track List shows the trackers in the behavior as Track 1, Track 2, and so on. The number
of trackers is determined by the number of control points on the shape with the applied
Track Points behavior. For example, when a Track Points behavior is added to a shape
with 12 control points, 12 trackers appear in the track list.
When another track is referenced, the track list is replaced with Control Point pop-up
menus.
To disable a tracker, deselect its checkbox. To remove a tracker, click the Remove button.
A tracker that is turned off is not analyzed with the track.
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: 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: Use this parameter to define 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. After 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.
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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.
• 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: Use this option if you have manually created track position
keyframes to guide the tracker. 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: Click or Control-click the color well to set a new color for the onscreen tracker.
You can also click the eyedropper and select a color in the Canvas. 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 the individual color channels,
including the tracker’s opacity, click the disclosure triangle.
Control Points:
When the Track Points behavior references another behavior, such as
Analyze Motion, the Track list parameters are replaced with the Control Point pop-up
menus. There is a pop-up menu for each control point on the shape. From the pop-up
menus, choose the track you want to assign to a control point.
Note: If you add or delete control points to a shape after you apply the reference track,
select the Track Points behavior in Inspector or Layers list to refresh the Control Point
pop-up menu list.
Tip: To check the number of any control point on a shape, you can select the shape in
the Layers list, choose the Edit Points tool from the toolbar, then click on a control point
in the Canvas.
HUD Controls
The Track Points HUD contains controls to load an animated object or tracking behavior
into the behavior (via the Source well or the tracking behaviors pop-up menu), to specify
how the destination object moves, to start the motion analysis (via the Analyze button),
to reverse the direction of the track (via the Reverse checkbox), and to offset the track
(via the Offset Track checkbox).