Adobe 12040118 - After Effects Standard Tutorial page 285

Interpolation works best when the mask paths have dense sets of vertices. Also, a vertex on the first mask path cannot match the middle of
a curve or straight-line segment on the second mask path, so sometimes you must add vertices before matching to produce the desired
result. Smart Mask Interpolation does not modify the original keyframes. Only the new mask path keyframes computed by Smart Mask
Interpolation have additional vertices.
The value you set specifies how finely the input mask paths are subdivided. Pixels Between Vertices specifies the distance, in pixels,
between vertices on the larger perimeter mask path after subdivision. Total Vertices specifies the number of vertices on the interpolated
mask paths. Percentage Of Outline specifies that a vertex is added at each indicated percent of the mask path outline length. For example,
a value of 5 means that a vertex is added at each successive segment of the outline that represents 5% of the total perimeter. To use only
the vertices that were on the path at the first frame, do not select this option.
Note: Smart Mask Interpolation may add vertices at existing vertex locations even if Add Mask Path Vertices is not selected. If two vertices
on one mask path match a single vertex on the other, the single vertex is duplicated at the same location so that the segment between the
two vertices shrinks to that location.
Matching Method Specifies the algorithm that Smart Mask Interpolation uses to match vertices on one mask path to vertices on the other.
Auto applies the matching algorithm for curves if either of the two selected keyframes has a curved segment; otherwise, it applies the
polylines algorithm. Curve applies the algorithm for mask paths that have curved segments. Polyline applies the algorithm for mask paths
that have only straight segments.
Note: The mask path keyframes added by Smart Mask Interpolation are polylines when Polyline Matching Method is selected, regardless of
whether the input mask paths contained curved segments.
Use 1:1 Vertex Matches
vertex on the other mask path. On each of the input mask paths, Smart Mask Interpolation matches the first vertices, the second vertices,
the third vertices, and so forth. If the two paths have unequal numbers of vertices, this action may produce undesirable results.
Specifies that Smart Mask Interpolation matches the first vertices in the two mask path keyframes. If not selected,
First Vertices Match
Smart Mask Interpolation searches for the best first-vertex match between the two input mask paths.
Note: To ensure good results, make sure that the first vertices of the input mask paths match, and then select First Vertices Match.
Additional resources about animating masks with Smart Mask Interpolation
Chris and Trish Meyer provide some tips on animating masks, including using Smart Mask Interpolation, on the
Move a mask or pan a layer behind a mask
You can adjust the area that is visible through a mask by either moving the mask in the Layer or Composition panel or panning (moving) the layer
behind the mask in the Composition panel. When you move a mask, the Position values of the masked layer remain constant, and the mask
moves in relation to other objects in the Composition panel.
When you use the Pan Behind (Anchor Point) tool to pan a layer behind a mask, the position of the mask remains constant in the Composition
panel but changes in the Layer panel. The Position values of the masked layer change in relation to the composition. As you pan past the edges
of the layer frame, the Mask Path values on the layer also change. Using the Pan Behind (Anchor Point) tool saves steps; without it, you would
have to change the Position and Mask Path properties of the masked layer manually. You can animate a layer panning behind another layer by
setting keyframes for the Position and Mask Path properties of the masked layer.
When you use the Pan Behind (Anchor Point) tool in the Composition panel, After Effects automatically makes two adjustments. In the Layer
panel, the mask is moved in relation to its layer (top), and in the Composition panel, the layer is moved in relation to the composition (bottom).
Specifies that Smart Mask Interpolation creates a vertex on one mask path that matches the same-numbered
ProVideo Coalition website.
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