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Chapter 4. 2-D Animation > Beyond Cel Animation

Beyond Cel Animation

Although cel animation techniques and tools are valuable to any animator, for some computer graphic animation effects, many of the traditional methods simply don't apply. A host of programs allow you to animate objects to create animated text, flying logos, and other 2-D effects that take advantage of multiple layers and transparency. There are also a growing number of useful—and sometimes bizarre—morphing and warping tools, which let you put the mojo on existing pictures.

A major difference between these keyframe animation programs and cel-animation tools is the fact that the keyframe tools offer automatic inbetweening—that is, you set up the keyframes, and the program calculates and generates the in-between frames for you. This procedure has the important advantage—or disadvantage, depending on your perspective—of removing the pencil artist from the equation. Instead, these programs are primarily used to animate the elements of graphic design: type, photography, and individual pieces of hand-drawn art. Many of these programs also work well with frames of video and film.

Compared with the traditional cel animation process, keyframe animation programs eliminate many of traditional steps. Table 4.1 draws some comparisons.

Table 4.1. Cel Animation vs. Keyframe Animation
Cel Animation Keyframe Animation
Exposure notes on the "dope sheet" are made for each event in the soundtrack corresponding to individual frames of animation.The soundtrack exists on the time line alongside visual elements, and art is aligned visually to synch to sound.
Key poses are drawn by hand, allowing for subtle changes in movement and expression of characters.Elements are imported and dragged into position at key times to create extreme frames.
Inbetweens are drawn by the animator or assistant animator.Inbetweens are automatically calculated by software.
Timing adjustments are made by adding and subtracting inbetween frames.Timing adjustments are made by dragging keyframes on the time line, modifying function curves, and applying automatic effects (such as slow in and slow out).
Inking and painting follow pencil tests.Animation is created from finished artwork, so inking and painting aren't required.
Animations are saved in final format, with a 1-to-1 correspondence between the number of frames drawn by the animator and the number of frames in the animation.Animations are rendered at any frame rate, with the number of inbetween frames determined by the frame-rate setting.


Admittedly, Table 4.1 makes some generalizations that don't always hold up. Macromedia Director and Macromedia Flash, for example, animate one frame at a time when they are working with hand-drawn cels, or they generate inbetween frames for objects moved from point to point or rotated.

Event-Based Time Lines vs. Keyframes

Early animation programs used the concept of simple pose-to-pose keyframes, but few programs still do. The distinction between keyframes and event-based time lines is simple in theory but has important effects on your animation in practice. In a keyframe animation program, you set a keyframe for an entire pose of animation, which effectively freezes the frame at that moment in time. You can then set another keyframe at a later state.

When you generate an animation, inbetween frames are generated to smoothly animate every element from their positions in one keyframe to their positions in the next keyframe. This technique works OK if you're animating only a single object. The trouble with this approach is that every element on-screen moves from its position in keyframe A to its position in key-frame B in a straight line. Also, every object is subject to the same timing, which results in stiff, unnatural movement if you're animating multiple objects, particularly if they're connected. It becomes impossible to animate natural movement of a walk, for example, because the hips move in a straight line rather than an arc, and if you add an extra keyframe to adjust the movement of the hips to more closely resemble an arc, the timing for the animation of the feet is thrown off.

On the other hand, keyframe animation works fine if you're animating only a single object.

Event-based time lines work on the same concept as key-frame animation, except that each object has its own time line and timing. This means that you can animate overlapping action and have fine control of the timing and motion of every object. (This is true in 3-D animation programs as well.) You can make the arms and legs of a character move to their own rhythms, even as the character itself arcs smoothly across the screen.

Time-Line Animation in After Effects

The following example describes the creation of a simple text animation in Adobe After Effects, to introduce the concept of time line animation:

  1. Create a new composition in After Effects and enter the values in Figure 4.19a in the Composition settings.

    Figure 4.19a. Composition setting.

  2. Choose Layer/New Solid, and set the size of the object to 50 × 30 pixels. (The color doesn't matter.)

  3. With the new solid selected, choose Effect/Text/Basic Text; type the text FLIP; and click the Center button. The font used in this example is Font House's Funhouse, but choose whatever you like, and click OK. The type should replace the solid box that you placed originally. Drag it into the position shown in Figure 4.19b.

  4. With the time marker at 0:00, click the keyframe switches in the position and rotation tracks of the text object. This sets a new keyframe on the time line for each of these values (see Figure 4.19b).

    Figure 4.19b. Setting a new keyframe on the time line for each value.

  5. Drag the time marker to 1:00 and click the checkbox in the position track of the text object to set a new keyframe. Because the object hasn't moved, these two keyframes cause it to hold in position for 1 second (see Figure 19c).

    Figure 4.19c. Holding in position for one second.

  6. Move the time marker to time 1:20, and drag the text to the new position shown in Figure 4.19d. Notice that this automatically causes a new keyframe to appear in the position track of the time line (see Figure 4.19d).

    Figure 4.19d. A new keyframe appears in the position track of the time line.

  7. Move the time marker to 2:20 and click the position checkbox again. This creates another hold from the last frame. The hold, move, and hold set up the anticipation of the main animation. See Figure 4.19e.

    Figure 4.19e. Setting up the anticipation.

  8. For the big move, drag the time slider to 9:00; then drag the text object to the far-right end of the composition window, as shown. Notice that another key frame is set automatically (see Figure 4.19f).

    Figure 4.19f. Another keyframe is set automatically.

  9. Click the play button in the Time Controls to preview the animation. Notice that you have anticipation and action but no personality (the object doesn't flip) and no arcs in the motion path.

  10. To correct the latter problem first, move the time slider to 5:10, grab the text object, and move it to the top of the screen as shown in Figure 4.19g. Notice that the long animation path is now a Bezier curve, which you can edit by dragging the control handles.

    Figure 4.19g. The long animation path is now a Bezier curve.

  11. To add the spin to the animation, add events to the rotation time line for the text object. Begin by moving the time marker to 1:00 and clicking the rotation checkbox. This keyframe creates a hold, just as you did for the position track.

  12. Move the time marker to 2:04, and click the Rotation value (expressed in degrees). In the dialog box, enter –40 degrees, and click OK. This setting causes the text to rear up, which completes the anticipation of the text jumping forward. Notice that this keyframe comes a little bit after the text moves to the back position, which causes a bit of overlapping motion to make the animation more interesting (see Figure 4.19h).

    Figure 4.19h. A bit of overlapping motion will make it more interesting.

  13. Move the time marker to 2:20, and click the rotation checkbox to set another hold. This causes the rotation of the text to freeze for about a half-second, so that the audience can see it before the text starts spinning forward.

  14. Move the time marker to 9:00, and click the rotation value set-ting. Set the value to 2 revolutions (clockwise). Again, this sets a new keyframe at the end of the animation (see Figure 4.19i).If you preview the animation, you see that it rotates and animates properly but has no slow in or slow out (called ease in and ease out in After Effects).

    Figure 4.19i. Setting a new keyframe at the end of the animation.

  15. Look at the motion curves for the position and rotation of the text object (see Figure 4.19j). The position graph shows two large table-top bumps with flat horizontal sections. This indicates that the position value changes from zero to some high speed very suddenly, progresses at a steady pace for a time, and then stops and becomes zero just as suddenly. You can see that there is one bump for the anticipatory backward movement and one bump for the forward animation. Similarly, the Rotation Velocity: Angle curve shows a downward bump, representing the backward anticipatory rotation, and an upward bump showing the forward rotation, with small flat spots in between representing the holds. These bumps also have flat horizontal lines for most of their length, indicating an instant acceleration to full speed and a steady rotational velocity until they stop in their tracks.

    Figure 4.19j. Two large table-top bumps with flat horizontal sections.

  16. After Effects lets you apply ease in and ease out simultaneously (see Figure 4.19k). Shift+select the two keyframes on the position track at time 1:00 and 1:20. Choose Layers/Keyframe Assistant/ Easy Ease. Notice the new smooth shape of the motion curve. Click the Play button in the Time Controls to preview the effect.

    Figure 4.19k. Applying ease in and ease out simultaneously.

  17. Shift+select the two event marks in the position track at 2:20 and 9:00 (see Figure 4.19l). Again, choose Layers/Keyframe Assistant/Easy Ease. This time, the command applies ease in/ease out once too often, affecting the keyframe that generates the arc in the path and causing the motion to slow to a stop and speed up in the middle of the main action. Select the two control handles for the curve at keyframe 5:10 and drag them up to smooth out the motion of the curve.

    Figure 4.19l. Selecting the two event marks in the position track.

  18. Repeat the steps to apply Layers/Keyframe Assistant/Easy Ease to the two pairs of event marks that define the rotation of the text (at 1:00-2:04 and 2:20-9:00). Preview the animation to see the effect of the motion-curve adjustments (see Figure 4.19m).

    Figure 4.19m. Check the effect of the motion-curve adjustment.

  19. Generate a QuickTime movie or animated GIF with the Composition/Make Movie command.

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