About Shapes, Masks, and Paint Strokes
Shapes and masks are vector-based objects drawn and edited using control points that
define mathematical curves. Each control point in a shape defines some sort of corner or
curve, and the actual spline that makes up the shape connects these control points
together like a connect-the-dots drawing. You can edit or animate any shape by moving
and editing its control points or by applying a Shape behavior.
Shape behaviors are designed specifically to be applied to shapes and masks, and perform
tasks such as oscillating the position of the control points, tracking the control points,
drawing a shape over time (“writing on”), as well as randomizing or wriggling the position
of the control points. As with all layers in Motion, you can also apply Basic Motion,
Parameter, and Simulation behaviors to shapes.
A paint stroke is a shape created in one of two ways: You can “paint” the stroke in the
Canvas using the Paint Stroke tool in the toolbar, or you can modify the outline of an
existing shape. The Paint Stroke tool allows you to use a stylus and graphics tablet (or a
mouse) to create a paint stroke, rather than drawing the shape in a point-by-point fashion
(like a Bezier or B-Spline shape). In addition to sharing other shape outline parameters,
paint strokes have a unique tool set that allows you to change the look of the paintbrush
and to create particle-type effects with the stroke. Paint strokes have a special behavior
called Sequence Paint, which allows you to sequence the stroke parameters over time,
including opacity, rotation, and scale.
The Paint Stroke feature is a design and graphics tool, not a retouching or rotoscoping
tool.
Note: Using a stylus and graphics tablet is recommended when using the paint feature.
Although you can create paint strokes using the mouse, a pen allows for a more fluid
creation of strokes.
Because shapes are mathematically defined, you can take advantage of the vector nature
of shapes to resize them by any amount, without introducing unwanted artifacts. Shapes
are similar to imported PDF objects in that they’re completely resolution-independent.
You can save a shape or a shape style to the Library. This means that after you create or
animate that shape, or both, you can save it to the Library for use in a future project. You
can also save just the style of a shape—such as a custom gradient fill or modified brush
stroke.
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Chapter 20
Using Shapes, Masks, and Paint Strokes