ADOBE AFTER EFFECTS 7.0
User Guide
268
Note: Regardless of the keyframe rate you choose, Smart Mask Interpolation always adds keyframes at the frame just
after the first mask shape keyframe and at the frame just before the second mask shape keyframe. For example, if you
interpolate between keyframes at 0 seconds and 1 second in a 30-fps composition with a keyframe rate of 10 per second,
mask shape keyframes are added at frame numbers 1, 3, 6, 9, 12, 15, 18, 21, 24, 27, and 29.
Keyframe Fields Doubles the keyframe rate. When this option is selected, and Keyframe Rate is set to the compo-
sition frame rate, a keyframe is added at each video field. Select this option for animated masking for interlaced
video. If this option is not selected, the mask may slip off the object that you are attempting to key out. For more
information about fields in interlaced video, see āAbout interlaced and noninterlaced videoā on page 98.
Use Linear Vertex Paths Specifies that vertices in the first keyframe move along a straight path to their corre-
sponding vertices in the second keyframe. Leave this option unselected if you want some vertices to interpolate along
curved paths; for example, when the desired interpolation involves rotating parts. If this option is not selected, Smart
Mask Interpolation creates a natural path for the mask.
Bending Resistance Specifies how susceptible the interpolated mask shape is to bending instead of stretching. A
value of 0 specifies that, as the mask shape animates, it bends more than it stretches; a value of 100 specifies that the
mask shape stretches more than it bends.
Quality SpecifieshowstrictlySmartMaskInterpolationmatchesverticesfromonekeyframetoanother.Avalueof
0 specifies that a particular vertex in the first keyframe matches only the same-numbered vertex in the second
keyframe. For example, the tenth vertex in the first keyframe must match the tenth vertex in the second keyframe.
A value of 100 means that a vertex in the first keyframe can potentially match any vertex in the second keyframe.
Higher values usually yield better interpolations; however, the higher the value, the longer the processing time.
Add Mask Shape Vertices Specifies that Smart Mask Interpolation adds vertices to facilitate quality interpolations.
In general, Smart Mask Interpolation works best when the mask shapes have dense sets of vertices. Also, a vertex on
the first mask shape cannot match the middle of a curve or straight-line segment on the second mask shape, so
sometimesyoumustaddverticesbeforematchingtoproducethedesiredresult.SmartMaskInterpolationdoesnot
modify the original keyframes. Only the new mask shape keyframes computed by Smart Mask Interpolation have
additional vertices.
The value you set specifies how finely the input mask shapes are subdivided. Pixels Between Vertices specifies the
distance, in pixels, between vertices on the larger perimeter mask shape after subdivision. Total Vertices specifies the
number of vertices on the interpolated mask shapes. Percentage Of Outline specifies that a vertex is added at each
indicated percent of the mask shape 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 there
at the first frame, do not select this option.
Note: Smart Mask Interpolation may add vertices at existing vertex locations even if Add Mask Shape Vertices is not
selected. If two vertices on one mask shape 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 SpecifiesthealgorithmthatSmartMaskInterpolationusestomatchverticesononemaskshape
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 shapes that have
curved segments. Polyline applies the algorithm for mask shapes that have only straight segments.
Note: ThemaskshapekeyframesaddedbySmartMaskInterpolationarepolylineswhenPolylineMatchingMethodis
selected, regardless of whether the input mask shapes contained curved segments.
Use 1:1 Vertex Matches SpecifiesthatSmartMaskInterpolationcreatesavertexononemaskshapethatmatchesthe
same-numbered vertex on the other mask shape. On each of the input mask shapes, Smart Mask Interpolation
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