Manipulating Keys

Once keys are set, they appear on the Timeline palette. These keys can be selected and moved by first selecting the keys and then dragging them to a new location in the Timeline palette. You select keys in the Timeline palette by simply clicking them, and they turn red when they are selected. You can also select multiple keys by dragging over them in the Timeline palette.

If you want to select all keyframes at once, you can use the Animation, Select All Keyframes menu command. When a key or a group of keys is selected, you can move them to a new frame by dragging them to the left or right. You can also use the Edit, Cut, Copy, and Paste menu commands to move keys. This feature is covered below.

Once a keyframe or a group of keyframes is selected, you can delete the selected keyframes by simply pressing the Delete button at the top of the Timeline palette or by holding down the Alt/Opt key and pressing the Backspace key.

If you want to remove all keyframes from the selected layer, you can use the Animation, Clear Animation from Layer; if you want to remove all keyframes from the entire document, you can use the Animation, Clear Animation from Document menu command. This last command is pretty heavy and will remove all keys, so a warning dialog box appears before this command is completed, warning you that this action cannot be undone.

Rescaling Keyframes

Although it is easy to move selected keyframes between frames, sometimes you want to keep the relative distance between adjacent keys without having to move each individual key. Using the Animation, Rescale Keyframes menu command, you can extend or reduce a section of animation without having to move each keyframe.

Scaling keyframes is an easy way to adjust the timing of your animation. If your objects are moving way too fast, then scaling to a larger number of frames will slow them down, and if your objects move too slowly, then try scaling the keys to a smaller range.

You can also rescale the selected keys by holding down the Alt/Opt key and dragging in the Timeline palette.

Selecting the Animation, Rescale Keyframes menu command opens the Rescale Keyframes dialog box shown in Figure 17.7. When the dialog box is first opened, the Start and End Frame values are automatically set to 1 and the frame of the last key is on the current layer.

Using the channel checkboxes, you can select precisely which channels on the current layer get scaled. However, if the Rescale Entire Document option is selected, all channels on all layers are scaled. This option also causes the End Frame to be automatically set to coincide with the frame of the last key from all layers. It also disables all the individual channels located at the bottom of the dialog box. This provides a way to scale all the keys across multiple layers at once.

The Rescale Keyframes dialog box can be used to scale ranges of keys, but it also can be used to shift a range of keys. If you specify a range of keys, such as 20 to 30, and then enter the New Start Frame and New End Frame as 40 and 50, then the keys within that range will be moved to the new location.

Copying and Pasting Keys

At the top of the Timeline palette are buttons you can use to copy and paste selected keyframes to another frame. Clicking the Copy button or pressing the Alt/Opt+C keyboard shortcut copies the current selection of keys into a temporary buffer. If you then move to another frame and click the Paste button or press the Alt/Opt+V keyboard shortcut, the copied keyframes are pasted in the current frame.

Looping Animations

An easy way to create a looping animation is to copy the beginning keyframe of an object to the ending frame. This causes the object to return to the exact position where it first started.

The Animation menu also includes a command to set the key values for all layer channels to match the value set at frame 0. The command is Reset All Layer Channels. This command provides a great way to create an animation that has all objects returning to their initial state. By setting the end locations for all objects to match the start, the animation will start looping without any jumps. To rescale keyframes to speed up an animation and to copy keys to create a loop, follow these steps:

1.	Open the Rolling tire.anme file from the Chapter 17 folder on the CD. This file includes an animated sequence of a tire rolling down a hill. It includes layer translation and rotation keys, but if you play the sequence, it moves too slowly.
2.	Select the Animation, Rescale Keyframes menu command to open the Rescale Keyframes dialog box. The Start Frame is automatically set to 1 and the End Frame is set to 60. Leave the New Start Frame at 1 and change the New End Frame to 18; then select the Layer Translate and Layer Rotation channels in the dialog box and click the OK button. The keys in the Timeline palette are scaled.
3.	In the Timeline palette, hold down the Shift key and click the key at frame 0 for the Layer Translate channel; then click the Copy button at the top of the Timeline palette.
4.	Drag the Time Slider to frame 30 and click the Paste button at the top of the Timeline palette. The copied key is added to frame 30.
5.	Click the Play button (Spacebar) to see the resulting animation. The tire now rotates quickly down the hill and bounces back to the start point, as shown in Figure 17.8. Figure 17.8. Rescaled and looping keys. [View full size image]