Animate and edit paint strokes – Adobe After Effects User Manual
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Note:
Animate and edit paint strokes
You animate a paint stroke by setting keyframes or expressions for its properties. After Effects animates paint stroke properties—even the Path
property of a paint stroke—by interpolating values for all frames between keyframes.
By modifying and animating the Start and End properties of a paint stroke, you can control how much of a stroke is shown at any time. For
example, by automatically animating the End property from 0% to 100% with the Write On setting, you can make a paint stroke appear to be drawn
on over time.
As with all properties, you can link paint stroke properties to other properties using expressions. For example, you can make a paint stroke follow a
moving element in your footage by tracking the moving element and then linking the Position property of the paint stroke to the Attach Point
property of the tracker.
Rotoscoping is a special case of painting or drawing on individual frames in which some item in the frame is being traced. Often, rotoscoping
refers to drawing animated masks rather than paint strokes. (See Rotoscoping introduction and resources.)
Scott Squires provides a pair of movies on his Effects Corner website that show how to rotoscope, both painting and masking:
Eran Stern provides a video tutorial on the
that shows how to animate a set of paint strokes to interpolate between several
hand-drawn pictures so that each morphs into the next.
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.
After Effects also includes a Write-on effect. (See Write-on effect.)
1. Select a paint tool in the Tools panel.
2. In the Paint panel, choose Write On from the Duration menu.
3. Drag in the Layer panel to apply a paint stroke to the layer.
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 within the layer in Layer panel. When you release the mouse button, the current time returns to the
time at which you started painting; this behavior is so that you can record more paint strokes for animated playback starting from the same
time.
You can animate the Trim Paths operation on a shape path to accomplish a similar result as animating a paint stroke with Write On. (See Alter
shapes with path operations.)
Animate a paint stroke path
1. Select a paint tool in the Tools panel.
2. In the Paint panel, choose Single Frame, Constant, or Custom from the Duration menu.
3. In the Layer panel, drag to create a paint stroke.
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