Parallel Corner Pinning Option (Pro Only); Perspective Corner Pinning Option (Pro Only) - Adobe AFTER EFFECTS 7.0 Manual

ADOBE AFTER EFFECTS 7.0
344
User Guide
After Effects gives you two corner-pinning options when tracking: Parallel Corner Pinning and Perspective Corner
Pinning. These options create multiple track points and apply them to the target layer using the Corner Pin effect.
See also
"Corner Pin effect (Pro only)" on page 423

Parallel Corner Pinning option (Pro only)

When you track using the Parallel Corner Pinning option, you simultaneously track three points in the source
footage. After Effects calculates the position of a fourth point to keep the lines between the points parallel. When the
movement of the points is applied to the target layer, the Corner Pin effect distorts the layer to simulate skew, scale,
and rotation, but not perspective. Parallel lines remain parallel, and relative distances are preserved.
For example, suppose that you have footage of a door shot by a handheld camera that zoomed in or out during
shooting but remained perpendicular to the door. You want to replace the door with a landing space ship. Using the
Parallel Corner Pinning option, After Effects calculates the relative movement between the feature regions to
correctly scale the space ship footage.
When you choose Parallel Corner Pinning, the default positions of the attach points form a rectangle in the center of the motion footage layer
(left). Moving the upper left tracking region moves the lower right (inactive) tracking region in tandem (center).
See also
"Corner Pin effect (Pro only)" on page 423

Perspective Corner Pinning option (Pro only)

When you track using the Perspective Corner Pinning option, you simultaneously track four points in the source
footage. When applied to the target footage, the Corner Pin Effect uses the movement of the four points to distort
the layer, simulating changes in perspective.
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 attach points to the four corners of the
sign. When the new image appears in the sign, After Effects calculates the relative movement between the feature
regions to create the correct perspective.
When you choose Perspective Corner Pinning, the default positions of the attach points form a rectangle in the center of the motion footage
layer (left). Moving each feature region extends the rectangle in the direction of motion (center).