Adobe 12040118 - After Effects Standard Tutorial page 217

longer matches the original feature. If the change is too great, After Effects may not be able to track the feature, and the track point will wander or
drift.
When the analysis begins to fail, return to the frame where tracking was still accurate and repeat steps 5 and 6: adjust and analyze.
Apply tracking data
If you're using any Track Type setting other than Raw, you apply tracking data by clicking Apply, after making sure that the correct target is shown
for Motion Target. You apply tracking data from a Raw tracking operation by copying keyframes from the trackers to other properties or by linking
properties with expressions.
You can also adjust the Attach Point or Attach Point Offset property after tracking in the Timeline panel, which can be useful when applying the
same tracking data to multiple targets that you want to distribute around the tracked feature.
Note: If the layer that you're attaching has motion blur enabled, make sure that the Shutter Phase value is set to -1/2 times the Shutter Angle
value. This combination of settings centers the motion blur on the attach point. Otherwise, the attached object may appear to lead or lag the object
that it's attached to.
You can apply the tracking data to a null object layer and parent the layer that you want to animate to the null object layer.
Track or stabilize motion with the point tracker
Tracking motion and stabilizing motion are essentially the same process, only with a different target and result. Use Track Motion to track motion
and apply the results to a different layer or effect control point. Use Stabilize Motion to track motion and apply the results to the tracked layer to
compensate for that motion (for example, to remove camera shake).
To stabilize a layer, After Effects tracks the motion of a feature in the layer that should be stationary in the frame, and then uses the tracking data
to set keyframes to perform the opposite motion. You can stabilize to remove any combination of changes in position, rotation, and scale, while
leaving desired motion unaffected. For example, if the camera is panning, deselect Position but select Scale and Rotation as the properties to
stabilize.
When you select Rotation or Scale in the Tracker panel, you set two track points in the Layer panel. A line connects the attach points; an arrow
points from the first attach point (the base) to the second. If possible, place the feature regions on opposite sides of the same object, or at least on
objects that are the same distance from the camera. The farther apart the regions, the more accurate the calculations and the better the result.
After Effects calculates rotation by measuring the change of angle of the line between the attach points. When you apply the tracking data to the
target, After Effects creates keyframes for the Rotation property.
After Effects calculates scale by comparing the distance between attach points on each frame with the distance between the attach points on the
start frame. When you apply the tracking data to the target, After Effects creates keyframes for the Scale property.
When you track motion using either parallel or perspective corner pinning, After Effects applies keyframes for the Corner Pin effect to the layer to
scale and skew the target layer as necessary to fit the four-sided area defined by the feature regions. The feature regions should lie in a single
plane in the real world—for example, on the side of a bus, on the same wall, or on the floor. The attach points should also all lie in a single plane,
but not necessarily the same plane as the feature regions.
Note: For parallel corner pinning only: To change which point is inactive, Alt-click (Windows) or Option-click (Mac OS) the feature region of the
point to make inactive. (One point must remain inactive to keep the lines parallel.)
1. Select the layer to track in the Timeline panel.
2. Do one of the following:
Click Track Motion in the Tracker panel (or choose Animation > Track Motion), click Edit Target, and choose the target to apply the
tracking data to.
Click Stabilize Motion in the Tracker panel (or choose Animation > Stabilize Motion). The target layer is the tracked (source) layer.
3. Select Position, Rotation, and/or Scale to specify what kinds of keyframes to generate for the target.
4. Move the current-time indicator to the frame from which to begin tracking.
5. Using the Selection tool, adjust the feature region, search region, and attach point for each track point.
6. In the Tracker panel, click either the Analyze Forward or Analyze Backward button to begin tracking.
If the tracking ceases to be accurate, click the Stop button , correct the problem as described in
analysis.
7. When you are satisfied with the position of the feature region and attach point throughout the track, click the Apply button to apply the
motion to the specified target.
After Effects creates keyframes for the target layer.
When tracking position and applying this position data to a target, you can choose to apply only the x (horizontal) or y (vertical) component
of motion. For example, you can apply the tracking data to the x axis to make a speech bubble (the motion target) remain at the top of the
frame even when the actor (the motion source) moves downward.
Correct a motion track, and resume
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