Track Points controls in Motion
The Track Points behavior (available in the Shape subcategory of Behaviors in the Library) lets you link the control points of a shape or mask (including paint strokes) to reference features on a source clip. This behavior also lets you apply tracking data recorded by the Analyze Motion, Match Move, or Stabilize tracking behaviors to the control points of a shape or mask.
After you apply a Track Points behavior to an object in your project, adjust the behavior using the parameter controls in the Behaviors Inspector:
Source: A well to specify the source object supplying tracking data. Drag a source object from the Layers list into the well. The source object can be another tracking behavior, a footage object, or an animated object. To clear a Source well, drag the thumbnail away from the well and release the mouse button.
Action pop-up menu: A pop-up menu (with a gear icon) to manually assign tracking data (from other tracking behaviors in your project).
Transform: A pop-up menu to set how the destination object moves. There are two options:
Attach to Source: Anchors the destination 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. You can preserve preexisting animation in the destination object by using the Adjust buttons (Position, Scale, and Rotation), available when the Type pop-up menu is set to Transformation.
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: Allows the destination object to “mimic” the recorded track or animation source. You can preserve preexisting animation in the destination object by using the Adjust buttons (Position, Rotation, or Scale).
Note: The destination object can be offset from the source object.
Align Tangents: A checkbox that, when deselected, forces tangents to 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.
Analyze: Three buttons used for the motion tracking analysis (available when the Source well contains footage):
Left arrows: Analyzes the portion of the clip before the playhead position.
Analyze: Analyzes the entire clip forward from the playhead position to the end of the clip (or to where the reference pattern can no longer be tracked).
Right arrows: Analyzes the portion of the clip after the playhead position.
Tracker Preview: A preview area (available when the Source well contains source footage) providing 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 you do so, the image moves around the red crosshair in the preview, and the tracker moves in the canvas.
Offset Track: A checkbox (available when the Source well contains source footage) that, when selected, lets you set a new tracker position when the original reference pattern becomes temporarily obstructed by an obstacle or goes off the screen. Motion uses the tracker position to continue the same tracking path begun by the original reference pattern. For more information on offset tracking, see Track obscured or off-frame points in Motion.
Auto-Zoom: A pop-up menu to 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 five options: None, 2x, 4x, 8x, and 16x.
Auto-Zoom Mode: A pop-up menu to set the display of the auto-zoomed tracker in the canvas. There are three options:
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 affect the Tracker Preview in the Behaviors Inspector.
Note: When Auto-Zoom is set to None, the Auto-Zoom Mode setting has no effect.
Look Ahead Frames: A slider and value slider 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, which helps the tracker follow fast-moving objects. For more information about the Look Ahead Frames control, see Advanced tracking strategies in Motion.
Track 1, Track 2, and so on: A list displaying the trackers in the behavior. To disable a tracker, deselect its checkbox. A deselected tracker is not analyzed. To remove a tracker, click its adjacent Remove button.
Note: When the Source well (described above) contains tracking data from another behavior (such as Analyze Motion), these checkboxes become pop-up menus used to assign which trackers (from the source tracking data) will provide anchor (position) data to the destination object, and which will provide rotation-scale data. And because trackers are no longer needed in the Match Move behavior, onscreen trackers are removed from the canvas.
To expose the following additional track controls, move the pointer over the track row, then click Show:
Position: Value sliders displaying the X and Y positions of the tracker.
Track Size: A slider to set (in pixels) the pattern search size for the tracker. As you adjust the tracker size, the Tracker Preview is updated to show the new pattern search size. However, there’s no visual change in the onscreen tracker.
Alternatively, you can adjust the Track Size parameter by Option-dragging left or right in the Tracker Preview area.
Search Size: A slider to set search area size for the tracker. In Motion, you do not specify the size of a search area when setting up trackers in the canvas. If your clip contains a lot of rapid movement, you may have better results increasing the Search Size. For example, if Search Size is set to 150%, the tracker searches 50% further beyond the Track Size setting.
Fail Tolerance: A slider to set the amount of tolerance for error, or confidence value, of the tracker. In other words, Fail Tolerance defines a threshold score at which the tracker determines it can match a reference feature. When the analysis yields a score above the Fail Tolerance value, the tracker accepts the match. When the score is below the value, the tracker rejects the match.
Fail Behavior: A pop-up menu to specify what happens if the track confidence value falls below the Fail Tolerance amount. There are six menu options:
Smart Retry: The tracker attempts to find the reference pattern in a larger search area. If the pattern still cannot be found, the tracker switches to the Predict option (described below). Smart Retry is the default Fail Behavior setting.
Stop: The analysis stops when the tracker loses the reference pattern.
Predict: The tracker predicts a new search area without creating keyframes until it finds a match for the reference pattern. This option is excellent for tracked elements that pass behind foreground elements.
Predict and Key: If a failure is detected, the tracker predicts the location of the next track point (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 reference pattern, the manually created tracking keyframes help guide the tracker.
Color: A color control to set a new color for the onscreen tracker. The default tracker color is red. A selected tracker is yellow. When a tracker is being positioned, its center crosshair 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. For more information about color controls, see Use basic color controls in Motion.
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