Adobe AFTER EFFECTS CS3 PROFESSIONAL User Manual page 316

See also
"Work with layer properties in the Timeline panel" on page 155
"Add, edit, and remove expressions" on page 545
Animate a paint stroke by sketching with Write On
If you choose Write On from the Duration menu in the Paint panel, the End property is automatically animated to
match the motion that you used to draw the stroke.
Note: After Effects also includes a Write-on effect. (See "Write-on effect" on page 437.)
Select a paint tool in the Tools panel.
1
2 In the Paint panel, choose Write On from the Duration menu.
Drag in the Layer panel to apply a paint stroke to the layer.
3
As you paint, your movements are recorded in real time and determine the rate at which the resulting stroke is drawn
to the screen for output. Recording begins when you click on the layer in Layer panel. When you release the mouse
button, the current time returns to the time at which you started painting; this is so that you can record more paint
strokes for animated playback starting from the same time.
Animate a paint stroke path
1 Select a paint tool in the Tools panel.
In the Paint panel, choose Single Frame, Constant, or Custom from the Duration menu.
2
3 In the Layer panel, drag to create a paint stroke.
Using the Selection tool, select the paint stroke.
4
To momentarily activate the Selection tool, press and hold V.
5 Press SS to show the selected paint stroke in the Timeline panel.
Click the triangle next to the paint stroke name to expand its list of properties.
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Click the stopwatch for the Path property to create an initial Path keyframe.
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Drag the current-time indicator to another time.
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While the stroke is still selected, drag in the Layer panel using a paint tool to create a paint stroke. A second Path
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keyframe appears in the Timeline panel.
By creating a stroke while a stroke is selected, you replace the selected stroke. This is sometimes referred to as stroke
targeting.
If you are not satisfied with the way that the path is interpolated, consider creating your path as a mask, using Smart
Mask Interpolation to fine-tune the interpolation, and then copying the Mask Path property keyframes to the paint
stroke Path property. (See "Use Smart Mask Interpolation" on page 264.)
After Effects interpolates a paint stroke (center) between two different shapes created with the same brush (left and right).
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