Apple Motion 5.1.1 - Manual (Page 881)

Chapter 20 Shapes, masks, and paint strokes 881
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Link: A checkbox available when you apply this behavior to a two-dimensional parameter
(such as Distort) or three-dimensional parameter (such as Position or Rotation) that
consists of X, Y, and/or Z values. Select this checkbox to keep the behavior’s effect on each
value proportional.
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Preserve Angle: A checkbox that causes the tangent handles to become (or remain) flat,
maintaining the continuity of the curves.
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Random Seed: A button that picks a new random seed number. This number is used to
randomly generate new sequences of values, based on the other parameters of this behavior.
Write On
The Write On behavior provides a quick way to draw a paint stroke or outline on the Canvas over
time. Write On lets you create a handwritten text effect, build the ever-popular old serial travel
map effect, create a hand-sketched alpha mask for a transition or reveal, draw an animated graph
for a business presentation, produce graphics to prevent monitor burn-ins, and so on. The Write
On behavior can be applied to a paint stroke created with the Paint Stroke tool or added to an
existing shape. You set the animation effect to draw, erase, draw and erase, draw in reverse, and
so on, over time.
When Write On is applied to a filled shape with an outline, 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.
Parameters in the Inspector
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Shape Outline: A pop-up menu that sets whether the stroke is drawn, erased, or drawn and
erased. Choose one of the following menu items:
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Draw: The stroke is drawn over the duration of the behavior.
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Erase: The stroke is completely drawn at the beginning of the behavior and is erased over
the duration of the behavior.
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Draw and Erase: The stroke is drawn, then erased over the duration of the behavior.
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Erase and Draw: The stroke is completely drawn at the beginning of the behavior, is erased,
then is drawn again.
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Stroke Length: A slider that 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%, when 50% of the stroke is drawn on,
it begins to erase (from the beginning of the stroke) so only half of the length of the stroke is
ever displayed over the duration of the behavior.
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Stroke Offset: A slider that 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.
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Direction: A pop-up menu that sets the direction in which the stroke is drawn. There are two
options:
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Forward: The stroke is drawn in a forward direction.
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Reverse: The stroke is drawn in reverse.
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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:
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Constant: The stroke is drawn at a steady speed from the first to the last point in the stroke.
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Ease In: The drawing of the stroke starts at a slow speed, then reaches and maintains a
steady speed through the last point on the stroke.
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