Chapter 9. Animation with Motion Tweening

9. Animation with Motion Tweening

Animating movement and changes to shapes by hand (frame-by-frame) is labor-intensive. Macromedia Flash 8 reduces the number of frames you must draw when you use a process called tweening. In Chapter 8, you created a three-frame animation of a bouncing ball by changing the position of the ball graphic in each of the three keyframes. Then you learned how to stretch out the animation by adding in-between frames that repeated the contents of the preceding keyframe. With tweening, you create similar keyframes, but Flash breaks the keyframe changes into multiple steps and displays them in the in-between frames.

To tween a graphic, Flash creates a series of incremental changes to that graphic; these changes are simple enough that Flash can describe them mathematically. Flash performs two types of tweening: motion tweening and shape tweening. This chapter covers motion tweening; Chapter 10 covers shape tweening.

Both types of tweening follow the same basic pattern. You give Flash the beginning and end of the sequence by placing graphic elements in keyframes. Then you tell Flash to spread the change out over a certain number of steps by placing that number of frames between the keyframes. Flash creates a series of images with incremental changes that accomplish the movement in the desired number of frames.

Drawing-Objects and Motion Tweening

Motion tweens require graphics that are in some form of container. In previous versions of Flash, to create a motion tween, the only graphic-container options were groups, symbols, or text boxes. Flash 8 gives you another choice: drawing-objects. When a drawing tool is set to Object Drawing mode, each shape it creates automatically winds up in a container. That means you can use a drawing-object directly in a motion tween without first converting the shape to a group or symbol.