Using Smart Mask Interpolation (Pro only)

Smart Mask Interpolation provides a high level of control for creating mask shape keyframes and smooth, realistic animation. Once you select the mask shape keyframes to interpolate, Smart Mask Interpolation creates intermediate keyframes based on settings you provide. The Info palette displays the progress of the interpolation and the number of keyframes created.


The Smart Mask Interpolation palette, showing the basic controls (left) and the optional controls (right)

To use Smart Mask Interpolation:

1. Choose Window > Smart Mask Interpolation.
2. Select at least two adjacent mask shape keyframes.
3. Set options in the Smart Mask Interpolation palette and click Apply.
4. If desired, click the arrows on the left corner of the palette tab or choose Show Options from the Smart Mask Interpolation palette menu, and set additional options.

Note: To interrupt the interpolation process, press Esc. The Info palette indicates that the process has been interrupted and reports the number of keyframes created.

Options in the Smart Mask Interpolation palette include the following:

Keyframe Rate

Specifies the number of keyframes Smart Mask Interpolation creates per second between the selected keyframes. For example, a value of 10 creates a new keyframe every 1/10 of a second. Choose Auto to set the keyframe rate equal to the composition frame rate, which appears in parentheses.

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 composition frame rate, a keyframe is added at each field.

Use Linear Vertex Paths

Specifies that vertices in the first keyframe move along a straight path to their corresponding vertices in the second keyframe. Leave this 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

Specifies how strictly Smart Mask Interpolation matches vertices from one keyframe to another. A value of 0 specifies that a particular vertex in the first keyframe matches only the same-numbered vertex in the second keyframe. For example, the 10th vertex in the first keyframe must match the 10th 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 adding vertices before matching is sometimes necessary to produce the desired result. Smart Mask Interpolation does not 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

Specifies the algorithm that Smart Mask Interpolation uses to match vertices on one mask shape 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: The mask shape keyframes added by Smart Mask Interpolation are polylines when the Polyline Matching Method is selected, regardless of whether the input mask shapes contained curved segments.

Use 1:1 Vertex Matches

Specifies that Smart Mask Interpolation creates a vertex on one mask shape that matches the same-numbered vertex on the other mask shape. On each of the input mask shapes, Smart Mask Interpolation matches the first vertices, the second vertices, the third vertices, and so forth. If the two shapes have unequal numbers of vertices, then this action may produce undesirable results.

First Vertices Match

Specifies that Smart Mask Interpolation matches the first vertices in the two mask shape keyframes. If not selected, Smart Mask Interpolation searches for the best first-vertex match between the two input mask shapes.

Note: To ensure good results, make sure that the first vertices of the input mask shapes match, and then select First Vertices Match.