11.0.
Introduction
Animation
can be defined as any visual
change over time. If an image does not change over a period of
time, it's impossible to tell whether it is a still image or an
animation. There are a variety of properties you can manipulate to
produce change, and thus animation. The most obvious is changing an
object's position to make it move. You can also change its size,
shape, rotation, transparency or color, to name a few. As long as
something changes visually, the viewer never sees the
animation.
In the earliest versions of Flash, most
animation was done by using tweens. An object was placed on a
keyframe, another keyframe
was made, and the object was changed in some way. Flash filled in
the frames in between, hence, the
term tween. Using ActionScript,
you can create much more dynamic and interactive animation.
As for what you can animate, a movie clip or
sprite is usually a good answer. These objects can contain
graphics, and they can have methods and properties that allow them
to be moved, scaled, rotated, and otherwise transformed any way you
see fit. A movie clip would normally be used only in the Flash
authoring environment, where additional frames are added, as in a
tween.
Finally, you need some way of getting the
changes to occur over time. Your best bet is either an enterFrame handler or a timer.
ActionScript statements can be used to make changes to the animated
object's properties on each frame, or timer cycle, if you're using
a timer. Since motion is the most obvious kind of animation, the
examples in this chapter start out by moving objects around. As the
chapter progresses, you'll see some examples that apply the same
techniques to other properties, such as animating the size of an
object or its orientation.
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