Animating Depth: Tweening Movement - Flash 3D: Animation, Interactivity, and Games - page 56

you to change an object's properties over time. Each frame in the Timeline represents
a single moment in time. By changing the content in each frame, you create an
animation. This chapter focuses on movement to enhance depth perception. When you
have finished reading the chapter, you will be able to
• Describe parallax scrolling
• Describe the animation concept of tweening
• Create motion tweens in Flash
• Reproduce camera movements in Flash
Parallax Scrolling
Remember the last time you were riding in a car looking out at the passing land-
scape. The car was moving at a consistent speed, but different parts of the landscape
appeared to be moving at different speeds. Objects farthest away, such as rolling hills,
appear smaller and move slower when compared to objects in the foreground that race
past the car. How does this happen?
The illusion is caused by two factors. One is your viewing position or vantage point,
and the other is the relative distance the objects are from you. Take a look at the fol-
lowing example (Figure 3.2). Imagine you are in a helicopter looking straight down
on three people crossing a street. Each person moves the same distance in the same
amount of time. From your viewpoint above, you witness a consistent speed and
distance traveled.
Figure 3.2 Top view