5

Four-Corner Pinning with Match Move
The Match Move behavior allows you to track four points on a background clip and apply
the recorded motion to the four corners of a foreground object. There are two basic
four-corner pinning workflows. In the first example, a foreground object is pinned to a
background element using the four-corner trackers. This workflow is useful when the
pinned image is the same size as the background reference patterns to be tracked. In the
second example, the foreground object is corner-pinned using onscreen controls before
applying the Match Move behavior. This method allows you to position, resize, and rotate
the foreground object to fit the background reference pattern.
Motion offers many tracking workflows because shots vary greatly, and tracking success
is unpredictable. Several tracking attempts are often required before a satisfactory track
is achieved.
Note: If one of the Match Move pinning options below doesn’t result in a successful track,
try four-point tracking using the Analyze Motion behavior or the Stabilize behavior. For
more information, see Using a Non-Match Move Four-Point Track for Corner-Pinning.
There are special considerations when corner-pinning groups. For more information, see
Tracking and Groups.
Option 1: Pinned Image Is Locked to the Reference Points
This workflow is ideal for a four-corner pin in which the transformed or pinned image is
the same size as the background frame (or reference patterns) it is being tracked to. In
the following example, a foreground image is pinned to a background clip of a picture
frame.
To track an image using four trackers
1 Drag the playhead to the frame where you want to start the track analysis, then apply a
Match Move behavior to the foreground object.
2 In the Behaviors Inspector, choose Four Corners from the Type pop-up menu.
Note: The Four Corners option is not available when Match Move is applied to a 3D group.
To corner-pin a 3D group, select the Flatten checkbox in the Group Inspector.
1304 Chapter 22 Motion Tracking