Animating Depth: Tweening Movement - Flash 3D: Animation, Interactivity, and Games - page 64

Step 5: Hide layers
With the composition in place, it is time to create the scrolling animation. Let's start
with the foreground layer. Before we do this, hide all the layers except the foreground
layer (Figure 3.14). This will allow you to see the Stage when creating the tweens.
Figure 3.14 Hiding all the layers except the foreground layer
Step 6: Create a movie clip
Currently the bitmap image of the foreground is contained within a graphic symbol.
Symbols help reduce the file size of the published Flash file. Flash stores the symbol
once in memory and allows you to create as many copies as needed without affecting
the file size. There are three types of symbols in Flash: movie clip, button, and graphic.
We are going to nest this graphic symbol in a movie clip. Why? Graphic symbols and
movie clips both contain their own Timelines, separate from the root Timeline that you
are working on now. However, when these symbols are placed on the root Timeline,
they behave differently. Let's examine this more closely.
A movie clip's Timeline plays independently from the root Timeline. If we create a
ten-frame animation in a movie clip and drag that movie clip to just one frame in the
root Timeline, Flash will play all ten frames when published even though the movie
clip occupies just one frame in the root Timeline. A graphic symbol's Timeline is linked
directly to the root Timeline. If we take the previous example and use a graphic symbol
instead of a movie clip, Flash will play only the first frame of the ten-frame animation
when published. In order to see all ten frames, the graphic symbol would need to occu-
py ten frames in the root Timeline.
To simulate a parallax scroll, each layer will contain a motion-tweened animation that
varies in lengths of time. We use the graphic symbol to create the motion tween.
Remember that motion tweens work only with symbols or grouped objects. This motion
tween is stored within a movie clip, which gives us the ability to layer several anima-
tions together on one frame. Each animation can then be different in time.