Apple Motion 3 - Manual (Page 1077)

Chapter 12 Using Shapes and Masks 1077
Write On
The Write On behavior provides a quick way to draw a paint stroke or outline on the
Canvas over time. This allows you to create a handwritten text effect, create the ever-
popular old serial travel map effect, create a hand-sketched alpha mask for a transition
or reveal, create an animated graph for a business presentation, produce graphics to
prevent monitor burn-ins, and so on. The behavior can be automatically applied to a
paint stroke created with the Paint Stroke tool or added to an existing shape. You can
have the shape draw, erase, draw and erase, draw in reverse, and so on, over time.
When Write On is applied to a shape, such as a circle or rectangle, only the outline of
the shape is drawn.
Note: You can manually animate the First Point Offset and Last Point Offset parameters
in the Style pane of the Shape Inspector to achieve the same effect as the Write On
behavior.
The Write On HUD contains the Shape Outline, Stroke Length, Stroke Offset, Direction,
Speed, and Custom Speed parameters. These controls, and the additional parameters in
the Inspector, are described below.
Parameters in the Inspector
Shape Outline: This pop-up menu determines whether the stroke is drawn, erased, or
drawn and erased.
 Draw: Draws the stroke over the duration of the behavior.
 Erase: The stroke is completely drawn at the beginning of the behavior, and is
erased over the duration of the behavior.
 Draw and Erase: The stroke is drawn, then erased over the duration of the behavior.
 Erase and Draw: The stroke is completely drawn at the beginning of the behavior, is
erased, then is drawn again.
Stroke Length: This slider defines the length, as a percentage, of the drawn or erased
stroke. A value of 100% uses the entire length of the stroke, bounded by the First Point
Offset and Last Point Offset parameters. If Stroke Length is set to 50%, once 50% of the
stroke is drawn on, it begins to erase (from the beginning of the stroke) so that only
half of the length of the stroke is ever displayed over the duration of the behavior.
Stroke Offset: This slider offsets where the stroke begins on the shape. The value is
expressed as a percentage of the total length of the shape from the start point defined
on the shape.
Direction: This pop-up menu sets the direction in which the stroke is drawn.
Speed: A pop-up menu that defines the stroke’s “draw-on” velocity from the first to the
last point in the stroke. There are nine options: