Adobe After Effects CS3 - Manual (Page 444)

AFTER EFFECTS CS3
User Guide
439
Rotation Animates the segments around the contour. For example, to create the appearance of running lights, start
with a large number of segments set to 50% of their length, and then animate Rotation to move the lights around the
shapes.
Random Phase Specifies that the stroke starting point is different for each contour. By default, the effect strokes a
contour beginning at its highest point on the screen. In the event of a tie, it starts at the leftmost highest point.
Blend Mode Determines how the stroke is applied to the layer. Transparent creates the effect on a transparent
background. Over places the stroke over the existing layer. Under places the stroke behind the existing layer. Stencil
uses the stroke as an alpha channel mask, filling the stroke with the pixels of the original layer.
Color Specifies the color of the stroke, unless Stencil is chosen for Blending Mode.
Width Specifies the width of the stroke in pixels. Fractional values are supported.
Hardness Determines how sharp or blurry the edges of the stroke are. A value of 1 creates a slight blur; a value of 0.0
blurs the line so that few solid areas of color remain.
Start, End Opacity Specify the opacity at the beginning or end of the stroke.
Mid-point Opacity Specifies the opacity of the midpoint of the stroke. This control works in terms of relative opacity,
not absolute opacity. Setting it to 0 makes the change in opacity smooth from the start point to the end point, as if
there were no midpoint at all.
Mid-point Position Specifies the location of the midpoint within a segment: Lower values move the midpoint closer
to the beginning; higher values move the midpoint closer to the end. Use this control to move the midpoint opacity
from the center of the stroke.
See also
“About randomness and random seeds” on page 354
Write-on effect
The Write-on effect animates strokes on a layer. For example, you can simulate the action of hand-writing of cursive
text or signatures.
Note: A convenient way to animate Brush Position is to use Motion Sketch to create Position keyframes on a new solid
layer and then use an expression on the Brush Position property to link it to the Position property on the new solid layer.
(See “Sketch a motion path with Motion Sketch” on page 199 and “Add, edit, and remove expressions” on page 549.)
This effect works with 8-bpc color.
Other methods of animating paint strokes and text are also available. For example, you can animate text by using the
type tools and text animators, and you can animate a paint stroke applied with a paint tool. Paint strokes can have a
Write-on Duration setting, which you can use to create similar results as with the Write-on effect. You can also
animate shape paths for a similar result with the Trim Paths operation. (See “Animating text” on page 285, “Animate
paint strokes” on page 310, and “Managing and editing shapes” on page 325.)
Brush Position The position of the brush. Animate this property to create a stroke.
Stroke Length (secs) The duration, in seconds, of each brush mark. If this value is 0, the brush mark has unlimited
duration. Use a single, constant, nonzero value to create a snakelike movement of the stroke. Animate this value to
make the stroke expand and contract.
Brush Spacing (secs) The time interval, in seconds, between brush marks. Smaller values produce smoother paint
strokes but take more time to render.