Flash-Tutorials - Shape Tween
Tweened animation is very important for two reasons. Tweened animation saves a lot of time because you do not have to draw every frame of the animation. Instead of that you define the first and last point and create the images for them. After that Flash software will interpolate, or fill the changes between them. Shape tween also helps to reduce the file size, because you will not have to save the content of every frame of the animated movie fragment. As you can set the content for first and last frames Flash will save only their content and the values of the changes made between them.
There are two types of tweening in Flash: shape tween and motion tween. Each of them has specific characteristics.
Shape tween is used to transform the drawn figures between the start and end points. Flash performs shape tweening only for the figures, so do not try to apply it for the group of objects, symbol or edited text - this will not work. You can perform the tweening for several figures on a single layer, but for the better arrangement of the elements, we recommend you to have every figure on a separate layer. If you will come back later to bring changes to this animated fragment this will be easier. If the same layer will contain several figures that shape tween was applied to you will be unable to understand anything.
You can also change the color of the objects during the shape tweening. When you create the shape tweening, the span is colored in green.
The simplest example of shape tweening is morphing (turning of one object into another).