3D Compositing with Action > Action: Surfaces > Modifying Surfaces >
Vertices Settings for Bilinear Surfaces

For bilinear surfaces, there are extra controls available in the Vertices tab.

(a) Offsets fields(b) Shape Channel button(c) Stabilizer controls(d) Vertex Translation fields(e) Reset Selection box(f) Edit Offsets button

Edit Offsets button and Offsets fields
  Edits tracker offsets. See Editing Tracker Offsets of a Bilinear Surface.
Stabilizer controls
  Use to apply stabilizing data to a surface or surface offsets.
Vertex Translation fields
  Verifies the coordinates of the currently selected vertex or tangent. You can modify these values to alter the shape of a surface. Press Ctrl and click the field to reset the selected vertex to its original position. See Changing the Shape of a Surface.
Shape Channel button
  Enable to use the Shape channel in the Channel Editor. Disable to use individual Vertex channels in the Channel Editor. See Reshaping Using the Channel Editor.
Sort button
  Enable to sort non-flat surfaces where overlapping transparent regions are causing artefacts.
Reset Selection box
  Select Reset Shape to reset the surface shape handles to their default position. The handles are reset in the current frame only. If Auto Key is enabled, a shape key is added at the current frame. Select Reset Points to reset selected points on the surface.