Apple Motion 5.1.1 - Manual (Page 965)

Chapter 22 Motion tracking 965
In the following example, an oval shape (the foreground object) is match-moved to a video clip
of picture frames (the background object) using two-point tracking. In the first three images
below, only Position is enabled in the Adjust row of the Behaviors Inspector. As a result, although
the camera pushes in toward the picture frames, the white elliptical shape does not change its
scale or rotation based on the position of the two trackers.
In the next example, Position, Scale, and Rotation are enabled in the Adjust row of the Behaviors
Inspector. Consequently, the white elliptical shape changes its position, scale, and rotation based
on the position of the two trackers, matching the camera’s push toward the picture frames and
preserving the illusion that the shape is physically attached to the picture frame.
Note: When using four-point tracking, scale and rotation are applied to the corner-pinned object.
Four-point tracking workflows
For more control over tracking, use the four-corner option, which lets you 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:
•
After applying the Match Move behavior, use four-corner trackers to pin a foreground object to a
background element: This workflow is useful when the pinned image is the same size as the
background reference patterns to be tracked.
•
Use onscreen controls to corner-pin a foreground object before applying the Match Move behavior:
This method lets you position, resize, and rotate the foreground object to fit the background
reference pattern.
Note: If one of the Match Move pinning options below don’t result in a successful track, try four-
point tracking using the Analyze Motion behavior or the Stabilize behavior as described below.
Use four-corner trackers to pin a foreground object to a background element
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.
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.
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