Corner-pin an object in Motion

You can use the Match Move behavior to track four points on a source clip and then apply the recorded motion to the four corners of a destination object. This process is known as corner pinning.

Note: Four-point tracking is only available when Mode is set to Point in the Match Move behavior.

Use four-corner tracking to pin a destination object to a source object

This workflow is ideal for a four-corner pin in which the transformed or pinned image is the same size as the source reference pattern it’s being tracked to. In the following example, an image is pinned to a source clip of a picture frame.

Tip: If the position, size, or angle of the destination object is radically different from that of the source pattern (an angled TV screen or picture frame, for example), you may need to adjust the object before you apply the Match Move behavior. You can reorient the object in the canvas using the Distort tool (available in the transform tools pop-up menu in the canvas toolbar).

In Motion, drag the playhead to the frame where you want to start the track analysis, then apply a Match Move behavior to the destination object.
By default, an object tracker is added to the center of the canvas.
Note: If you apply the Match Move behavior to a 2D group (rather than an individual layer in a group), make sure the Fixed Resolution checkbox is selected in the Group Inspector. When you apply the Match Move behavior to a 3D group, the Four Corners option is not available. To corner-pin a 3D group, select the Flatten checkbox in the Group Inspector.
In the Behaviors Inspector, click the Mode pop-up menu, then choose Point.
In the canvas, the object tracker changes to a point tracker. Because the default Match Move tracker records position data, it’s known as an anchor tracker.
In the Behaviors Inspector, click the Type pop-up menu, then choose Four Corners.
In the canvas, a point tracker appears at each corner of the destination object’s bounding box. In the Inspector, the Anchor and Rotation-Scale checkboxes are replaced with the Top Left, Top Right, Bottom Right, and Bottom Left checkboxes; each checkbox activates or deactivates a tracker in the canvas.
In the canvas, drag each tracker to a corner of the source object (in this example, the corners of the picture frame).
As you drag a tracker, a magnified inset appears to help you position each tracker.
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 behavior analyzes the movement of the reference pattern in the video clip, and the destination object is pinned to the source object; four motion paths show the transformation occurring at each corner.
If necessary, make minor adjustments to the destination object (such as modifying scale or rotation) by doing the following:
1. Click the Transform pop-up menu in the Behaviors Inspector, then choose Mimic Source.
  The default option in the Transform pop-up menu (Attach to Source) does not permit transformations of the object.
2. Open the Properties Inspector and make any necessary adjustments to the object using the Scale slider, Rotation dial, or other controls.
For more information on the Mimic Source and Attach to Source transform options, see Match Move controls.

If corner pinning does not produce a successful track

If the Match Move corner pinning method described above fails to yield a successful track, try four-point tracking using the Analyze Motion behavior. In this workflow, the four-point tracking data collected from the Analyze Motion behavior is loaded into a Match Move behavior to corner-pin a destination object.

In Motion, go to the frame where you want to start the track and apply an Analyze Motion behavior to the source object.
Important: Whereas the Match Move behavior is always applied to the destination object, the Analyze Motion behavior is always applied to the source object (clip).
By default, an object tracker appears in the canvas.
In the Behaviors Inspector, click the Mode pop-up menu, then choose Point.
In the canvas, the object tracker changes to a point tracker.
In the canvas, drag the tracker (Track 1) to a reference pattern in the top-left corner of the source object.
In the Behaviors Inspector, click Add to add a second tracker, then in the canvas drag the second tracker (Track 2) to a reference pattern in the top-right corner of the source object.
Add another tracker (Track 3), then drag it to a reference pattern in the bottom-right corner of the source object.
Add another tracker (Track 4), then drag it to the reference pattern in the bottom-left corner of the source object.
Positioning the point trackers in a clockwise order (starting in the upper-left corner) ensures the proper alignment of your element when the transformation is applied.
Note: To modify parameters for any of the trackers, position the pointer over the right side of the track parameter row and click Show.
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 track is generated and its data is saved in the behavior.
Apply a Match Move behavior to the destination object you want to corner-pin.
By default, an object tracker is added to the center of the canvas.
In the Behaviors Inspector, click the Mode pop-up menu, then choose Point.
In the canvas, the object tracker changes to a point tracker.
In the Match Move area of the Behaviors Inspector, click the Action pop-up menu (with the gear icon), then choose the Analyze Motion track.
The Analyze Motion tracking data recorded in step 6 is applied to the Match Move behavior.
In the Match Move area of the Behaviors Inspector, click the Type pop-up menu, then choose Four Corners.
Trackers are placed in the correct order (clockwise from the top left) in the canvas and the four-point tracking data from the Analyze Motion behavior is applied to the destination object.

Remove parallax from tracked 3D groups

When you match move 3D groups that contain objects offset in Z space (depth), parallax is simulated. Parallax is the apparent shift of an object against a distant background caused by a change in perspective, such as a change in camera position. You can disable this effect, if necessary, by doing the following:

In Motion, select the Flatten checkbox for the tracked group in the Group Inspector.
The parallax effect is removed.

For a full description of Match Move parameters, see Match Move controls.

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Helpful?

Motion User Guide

Corner-pin an object in Motion

Use four-corner tracking to pin a destination object to a source object

If corner pinning does not produce a successful track

Remove parallax from tracked 3D groups