User Guide

CHAPTER 13
402
Using Property and Tracking Controls (PB only)
3 Place the three track points at the locations where you want to attach the three corners
of the second layer. You can place the track points in the center, in the corner, or outside
the feature regions.
In this sequence, the three active feature regions are placed on three corresponding markers in the
motion footage layer. Each search region is slightly extended in the direction of its track point’s
motion. The track points are placed in the center of the feature regions.
Tracking position using perspective corner pinning
When you track position using perspective corner pinning, you are simultaneously
tracking four points in a motion footage layer with four corners in a second layer. As the
four points move, the layer is distorted to simulate perspective. The Tracker/Stabilizer
applies the Corner Pin effect to the second layer, generating keyframes for the layer and
Corner Pin-effect keyframes for each corner.
As with affine corner pinning, you can place the track points for perspective corner
pinning anywhere in the motion footage layer; they do not need to be in the center or in
the corner of the feature regions. For example, if you are replacing a sign on the side of a
moving bus, the edges of the sign may be partially obscured because of shadows or objects;
but a window on the bus may be visible throughout the footage. You can first define four
feature regions that are distinct and easy to track, and then move the track points to the
four corners of the sign. When the new image appears in the sign, the Tracker/Stabilizer
calculates the relative movement between the feature regions and track points to create the
correct perspective.
UG.book Page 402 Wednesday, February 21, 2001 12:05 PM