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Tracking position using affine corner pinning (PB only)


    When you track position using affine corner pinning, you simultaneously track three points in a motion footage layer with three points in a second layer. The position of a fourth, inactive point is determined by the three active points. As the three points move, the layer is distorted to simulate skewing, scaling, and rotation, but not perspective. Parallel lines remain parallel, and relative distances are preserved. For example, suppose that you have footage shot by a handheld camera that zoomed in or out during shooting but remained perpendicular to the background; you want to replace the background. Using affine corner pinning, the Tracker/Stabilizer calculates the relative movement between the feature regions and track points to create the correct scaling of the background.

    Place the track points anywhere in the motion footage layer; they do not need to be in the center or in the corner of the feature regions. 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.

    When you choose affine corner pinning, the default positions of the track 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). You can place the track points anywhere in the motion footage layer (right).
    When you choose affine corner pinning, the default positions of the track 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). You can place the track points anywhere in the motion footage layer (right).

To define tracking regions for affine corner pinning:

  1. Specify the tracking region that will be inactive by Alt-clicking (Windows) or Option-clicking (Mac OS) the region.
  2. Place and resize the three active feature and search regions over the areas you want to track.
  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.
  4. 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.
    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.