Most people, when they think of animation, think of things moving around on the page. Although this isn't the only kind of animation you can create, it's useful and straightforward, and serves as a good introduction to working with the timeline. Animating a layer's position involves three main steps:
Adding the layer to the timeline.
Establishing its starting position (at the first keyframe).
Establishing its ending position (at the second keyframe).
Adding a Layer to the Timeline
To be animated, a layer must be present on the timeline as a sprite. Create a layer, access the timeline (choose Window > Timelines), and do one of the following:
Drag and drop. In the Document window, grab the layer by its edge or its tab, and drag it into the timeline. Figure 1 shows this happening. This doesn't disturb the position of the layer in the document, but it does create a sprite representing the layer in the timeline.
Figure 1 Using drag and drop to add a layer to the timeline.
Using a Menu Command. In the Document window, select the layer. Choose Modify > Timelines > Add Object to Timeline. Figure 2 shows this happening.
Figure 2 Using a menu command to add a layer to the timeline.
Creating Tweened Motion
After the layer is in the timeline, note that its sprite begins and ends with a keyframe (a tiny circle icon in the sprite). Clicking in the middle of the sprite selects the entire sprite, but clicking either keyframe selects only that keyframe. Animated motion in the Dreamweaver timeline is created by specifying a starting and ending position and letting Dreamweaver tween the intermediate positions.
To establish the starting position: In the timeline, select the first keyframe of the sprite. In the Document window, drag or nudge the layer to its starting position; alternatively, in the Property inspector, change the L and T properties to reposition the layer.
To establish the ending position: In the timeline, select the second keyframe of the sprite. In the Document window, drag or nudge the layer to its starting position; alternatively, in the Property inspector, change the L and T properties to reposition the layer.
That's it! If you correctly selected the individual keyframes before repositioning your layer, and you have the layer selected, you will see a thin gray line in the Document window, indicating the path the tweened motion will follow. Dreamweaver will automatically supply the tweening between the two positions.
Figure 3 shows a sprite correctly set up for tweening between two keyframes. The timeline shows the sprite with its two keyframes. In the Document window, the motion line indicates how the layer will animate.
Figure 3 A Dreamweaver document set up for tweened layer animation.
Changing the Speed of the Animation
The number of frames involved and the frame rate, or fps, determines animation speed. The simplest way to slow down or speed up a particular animation is to alter the sprite length so that it occurs over more or fewer frames. To do this, just grab and drag the final keyframe of the sprite.
Although it is also possible to change speed by changing the frame rate, remember that the fps governs the quality of the animation as much as its speed. The lower the fps, the more jerky the animation will become. The higher the fps, the smoother the animationbut browsers cannot usually keep up with speeds higher than about 15 fps. Figure 4 shows different ways of changing an animation's speed.
Figure 4 Timelines showing a tweened animation being slowed down by lengthening the sprite and by lowering the frame rate.
Creating Complex Motion Paths
Dreamweaver tweens motion in a straight line between two keyframes. Every change of direction in the motion path requires a new keyframe.
To add a keyframe to a sprite, do one of the following:
Hold down the Ctrl key (Windows) or the Cmd key (Mac) and position the cursor over a sprite. The cursor turns into a tiny circle. Click on the sprite to add a keyframe. Figure 5 shows a keyframe being added to a sprite using this simple, quick method.
Figure 5 Ctrl/Cmd-clicking to add a keyframe to a sprite in the timeline.
Select the sprite. Move the playback head to the frame where you want the keyframe inserted. Choose Modify > Timeline > Add Keyframe.
To remove a keyframe from a sprite, select the keyframe to remove. Choose Modify > Timeline > Remove Keyframe.
Figure 6 shows an animation with a fairly complex motion path and the keyframes needed to create it. Note that after keyframes have been added within a sprite, they can be dragged back and forth to adjust the timing of the motion.
Figure 6 The Timelines panel, showing a complex motion tween consisting of several keyframes.
Making the Animation Play
To set the animation to play as soon as the page loads, in the Timelines panel select the Autoplay option. When you do this, the Play Timeline action is being added to the document using an on onLoad event so that the timeline will start where the page loads.
To set the animation to play only when a user triggers it, perform the following steps:
In the Timelines panel, make sure the Autoplay option is not selected.
Elsewhere in your document, create an image, text link, or form element that will trigger the animation.
With the triggering object selected, open the Behaviors panel and choose Timeline > Play Timeline from the plus (+) list.
Looping the Animation
By default, the timeline will play through once and stop. To make an animation loop, select the Loop option in the Timelines panel. When you do this, Dreamweaver might open an alert window explaining that a new behavior is being added to the timeline. You'll also see an indicator in the B (behaviors) channel of the timeline, representing the looping behavior.
Sprites hold animation instructions in the form of keyframes. Each sprite is associated with an object (for example, a layer) that it animates. After you get used to these concepts, you can be sneaky and manage your sprites efficiently.
To change the object that a sprite animates: Select the sprite and choose Modify > Timeline > Change Object. This can be especially useful if you've already created a complex motion path in a sprite and don't want to recreate it just because you've changed your mind about what layer you want to animate.
To duplicate a sprite: Select the sprite and choose Edit > Copy, then Edit > Paste. The duplicated sprite will appear immediately following the original in the timeline. You can then move it to where you want it. Used in conjunction with changing a sprite's target object, this means you can create a complex motion path and then use that path animate to multiple layers in your document.
To remove a sprite entirely from the timeline: Select the sprite and choose Modify > Timeline > Remove Object. Note that this doesn't delete the layer the sprite is animating. It only deletes the animation instructions.
When you delete a page element that is associated with a sprite, that sprite disappears from the timeline.