Task: Making a Sun Flicker
- In frame 1 of a new file, draw a sun with radiating rays (as in Figure 7.10).
Figure 7.10 The sun image that we're going to make blink.
Save the sun into the library. Select the entire image and then select Insert, Convert to Symbol. Name it sun, leave it in the default Movie Clip behavior, and click OK.
Click in the Timeline on frame 10 and drag to the left. This will select all the frames from 1 to 10. Notice that we went from 10 to 1. It's just a little touchy going the other direction. The safest way to select multiple frames is to hold down the Shift key. If you click and drag from frame 1 you won't have a problem. But if you click once on frame 1 and then click and drag, you'll move the keyframe. It turns out that there are even more ways to edit frames, especially when you change the span-selection option under Edit, Preferences, General.
With the first 10 frames selected, choose Modify, Frames, Convert to Keyframes, which should place a keyframe containing the contents of frame 1 into each frame.
Click the keyframe in frame 2. The red current frame marker moves to frame 2, and the contents of this frame are selected.
Select Edit, Clear (or better yet, click your Delete button). You've just created a keyframe with no onscreen imagealso known as a blank keyframe. This is shown as a hollow circle in the cell of the Timeline, as shown in Figure 7.11.
Continue to click the even-numbered keyframes and delete the onstage contents of each. Although you're deleting, it is the onstage contents that are being removed, not the keyframe itself. The blank keyframes are the same as normal keyframes, except there's nothing on the screen. You can prove this by drawing something onstage for an even-number frame. You'll see it turn back into a regular keyframe, with the solid dot and all.
Figure 7.11 After we insert an identical keyframe in every frame, we delete the contents in alternating frames (shown here after deleting the contents of frame 2).
Test your movie to see how this blinking effect looks. How would you lengthen the time the image remains onscreen? What if you want to lengthen the time it's not onscreen? Here's where incorporating pauses comes in.
To make the image stay on longer, just click on a keyframe that has contents (those with a solid dot in the Timeline) and select Insert, Frame (or press F5). Notice that the "life" of the image in each blink is lengthened. You can continue to insert frames after any keyframe (or blank keyframe), and whatever is in that frame will stay longer.