Motion Tweening
       by kirupa  |  7 October 2005

Animation in Flash revolves around the timeline. In your timeline, you can specify a starting point and an ending point for a particular event. I use the word point as opposed to time, for the concept of time in Flash is different than in the real world. In the real world, you measure the time it takes to do something in seconds or minutes or hours. In Flash, the primary measure of time revolves around frames, and the seconds/minutes of an animation are dependent on your frame rate.

So, where does motion tweening fit into all this? When you create a simple animation in Flash, you always specify a starting frame and an ending frame. For example, you could specify a ball to be at the left end of your stage at Frame 1:

[ your ball on the left side of the stage ]

You then create a keyframe, for example, on Frame 20 and move the same ball to the right end of your stage:

[ your ball on the right side of the stage ]

If you preview your animation, you will see your ball start at the left end of your stage and suddenly, when you reach Frame 20, appear at the right. There is no smooth transition between the beginning and starting positions of the ball. Here is where motion tweening comes in.

Motion tweening creates a transition between your ball at Frame 1 and Frame 20. Flash automatically calculates where your ball's position would be between Frames 2 and 19, so that when you preview your animation, your ball gradually moves from its initial left position to its right position. All you do is specify the beginning and end frames. Flash takes care of the rest!

In this tutorial, I will try to explain tweening by helping you create a simple tween with a few twists. The following animation is an example of what one of your animations could look like from following this tutorial:

[ a quick motion tween animation ]

Let's get started:

  1. First, download and open the FLA I have created. Don't worry, it only contains the bare minimum of items so that you don't have to spend time focusing on nonessential things:

Download Partial Source

  1. After you have opened the FLA, you should see a blue circle in the middle of your screen...and nothing else. Right click on Frame 25 in your timeline and select Insert Keyframe:

[ insert keyframe on Frame 25]

  1. You should see a keyframe on Frame 25. Now, insert a keyframe on Frame 50 also. Your timeline should have a keyframe on Frame 1, Frame 25, and Frame 50.
  2. Let's modify our circle's size. Go back to Frame 25 on your timeline, right click on your circle, and select Free Transform. The scale and skew boxes should appear around your circle. Click on any of the boxes on the corners and drag outward:

[ scale your circle larger ]

  1. If you were to preview your animation by pressing Ctrl + Enter, you will see that your circle starts off small, suddenly becomes bigger, and then returns to its small size again. Let's make this better.
  2. Select all of the frames in your timeline from Frame 1 to Frame 50. Right click on any of the selected frame(s) and select the option for Create Motion Tween.
  3. Notice that when you preview your animation, the circle smoothly animates from being small to large and back again.

Hopefully the above example helps you to visualize what I was explaining in the first part of this tutorial. It simply creates a fluid transition between different states of the object that your trying to animate.

In the next page, I will show you how to improve your tween by adding some tweening effects, explain some cases where tweening will not work as expected, and more!

Onwards to the next page!

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