Track shapes, masks, and paint strokes in Motion

You can use the Track Points behavior (located in the Shape Behaviors category) with shapes, masks, and paint strokes to:

Match the control points of a shape, paint stroke, or mask to points or patterns in a video clip (for example, when rotoscoping)
Apply tracking data recorded by the Analyze Motion, Match Move, or Stabilize behaviors to the control points of a shape or mask
Apply the animation of one shape (or other object) to the control points of another shape or mask

Note: To apply the analyzed movement of an object to a shape or mask as a whole (rather than to the shape’s individual control points), use the Match Move behavior.

Track a mask using the Track Points behavior

In the following example, the Track Points behavior is applied to a mask with many control points, isolating a plane in a video clip.

With a clip visible in the Motion canvas, use a mask tool to isolate part of the clip.
For more information on working with masks, see Intro to masks and transparency.
In the Layers list, select the mask object, then click Behaviors in the toolbar and choose Shape > Track Points.
The tracker is applied to the mask and track points.
Note: If necessary, drag the footage containing the object you are isolating to the Track Point’s Source well in the Behaviors Inspector.
Trackers appear for each control point on the shape. The trackers are arrayed in the same order that the shape was drawn: Control Point 1 is Track 1, Control Point 2 is Track 2, and so on.
Drag the trackers to fine-tune their positions on the reference patterns of the source footage.
As you drag, a magnified inset view of the area around the tracker appears.
To disable a tracker, deselect its checkbox in the Behaviors Inspector.
Note: Control points without an associated tracker are not modified.
In the Behaviors Inspector (or HUD), do one of the following:
- Analyze the clip forward from the position of the playhead: Click Analyze.
- Analyze the portion of the clip before the playhead position: Click the left arrows next to the Analyze button.
- Analyze the portion of the clip after the playhead position: Click the right arrows next to the Analyze button.
The mask control points are tracked to the reference patterns in the source footage.
The image on the left shows the original unmodified clip. The image on the right shows the tracked mask isolating the plane, allowing separate effects to be applied to the plane and its background even though they’re part of the same image. The mask protects the plane from the results of the color effects, blur, and cloud generator.
As with all behaviors, you can drag or copy (by Option-dragging) a Track Points behavior to a new shape in the Layers list. When you apply the behavior to a new shape, the trackers are applied to the control points of the new shape. If the new shape has more control points than the originally tracked shape, only the original track points are applied. For example, if the originally tracked shape has three control points, and the new shape has five control points, trackers are applied to the first three control points of the new shape. If the new shape has fewer control points than the originally tracked shape, trackers are applied to the existing points on the new shape.
Note: Paint strokes usually have a large number of control points. Simplify a paint stroke by deleting or disabling control points before applying a Track Points behavior to the stroke. To track the stroke as a whole, rather than by its control points, use the Match Move behavior. For more information about paint strokes, see Intro to paint strokes.

Apply the animation of one shape to the control points of another shape

Applying the animation of one animated shape to another is an easy way to create fun, complementary animations in which the objects appear to play with each other. For this workflow, your project must contain an object animated with keyframes or behaviors.

In a Motion project that contains two shapes, animate one of the shapes using keyframes or a Basic Motion behavior.
In this example, a simple line shape is animated with the Spin behavior.
For more information about animating with keyframes, see Intro to keyframing. For more information about Basic Motion behaviors, such as the Spin behavior, see Intro to basic Motion behaviors.
In the Layers list, select the nonanimated shape, then click Behaviors in the toolbar and choose Shape > Track Points.
Note: When you apply the Track Points behavior to a simple shape, a dialog appears. Click Add to convert the shape’s geometry to control points.
Drag the animated shape from the Layers list to the Track Points behavior’s Source well in the Behaviors Inspector.
Note: If the nonanimated shape is positioned immediately above the animated shape in the Layers list when the Track Points behavior is applied, the animated shape is automatically used as the Track Point behavior’s source.
A thumbnail of the animated object appears in the Source well of the Track Points Behaviors Inspector.
In the Behaviors Inspector, click the Transform pop-up menu, then choose Attach to Source.
The spinning animation of the line is applied to the Bezier shape, which spins and changes shape because the vertex tangents match the transformation of the source animation.
To align the tangents to the transformation of the source object, select the Align Tangents checkbox in the Behaviors Inspector.
The spinning animation of the line is applied to the Bezier shape, which now spins and but does not change shape because its vertex tangents remain aligned at their original angles along the shape.
Note: By default, the Transform pop-up menu is set to Mimic Source.

For a full description of the Track Points parameters, see Track Points controls.

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Motion User Guide

Track shapes, masks, and paint strokes in Motion

Track a mask using the Track Points behavior

Apply the animation of one shape to the control points of another shape