© Joel Hagen
One of the limiting factors in producing animations against a deadline
is the large number of frames required for even a few seconds of running
time. This beginner's column will explore some basic principles that can
help you extend the mileage of your animation efforts, making ten frames
do the work of a hundred.
Understanding the concept of creating cyclic motion is fundamental. For
example, to animate a spinning planet you need only create one full rotation.
That motion cycle can then be played in an endless loop. The time invested
in a few frames can yield many seconds of animation.
From the standpoint of the number of original frames required, reciprocal
motion is even more efficient than cyclic motion. One complete reciprocal
motion consists of a sequence of frames run forward then backward in what
is often called a ping-pong motion. For a waving cartoon character you
might only draw 6 frames of the arm moving from left to right. Those same
frames can then be played in reverse to have the arm wave from right to
left. That cycle can be looped for as long as needed.
Computer artists can take advantage of animbrushes
in Deluxe Paint and other programs to further increase animation mileage.
A brief motion cycle can be used as a repeating animated brush in a longer
animation, even moving through space as it loops. Applying animbrushes
to the concept of cyclic motion, you might create a single walk cycle for
a character in 10 frames. That can be used as an animbrush in a 100 frame
animation to have the character walk smoothly across the screen. Applying
the same idea to reciprocal motion, you could have a bird flap its wings
as it flies across the screen. You might only draw 6 frames of the wings
moving from their down position to their up position. This animbrush can
then be automatically set to "Ping-Pong" for the full up and
down cycle.
By modifying a reciprocal motion you can add character to a sequence. For
example, the bird might look more realistic if its downward flap was faster
than its upward flap. Pick up the 6 frame upward flap as an animbrush then
create a blank 8 frame animation. Stamp the six cels of the animbrush in
place on the first six animation frames. For the next two frames, manually
locate two intermediate cels of the animbrush to create a swifter downward
movement (in DPaint, the "7" and "8" keys move you
backward and forward through the cels of the animbrush). You now have a
cyclic 8 frame animation which can be picked up and used as an animbrush.
These basic techniques are effective ways to stretch the running time of
your work, but repeated motion can have a predictability that loses the
viewer's interest. Two ways you can address this problem are by interrupting
a looping cycle or by having a repeating cycle affect its surroundings.
As an example of interrupting a loop, you could have the flapping bird
fly across the screen as described but insert a glide in the middle of
the sequence. This could be as simple as repeating a single cel from the
middle of the flap cycle for several frames before returning to the flap
loop. No extra drawing is required and the character of the animation is
enhanced.
To experiment with the idea of a cyclic loop affecting its surroundings
you might go through the stages of creating the "Sculptor" animation
as shown in the accompanying illustration. The plan is to create a reciprocal
motion of a sculptor striking a chisel. Repeated blows gradually transform
a large block of stone into a finished sculpture.
If you have a digitizer you might try "rotoscoping" the character by drawing directly on successive photographs. You might pose a model for each position of the movement and digitize straight into the computer. Lacking a model, I posed in front of a video camera using cardboard props for hammer and chisel. I later used GVP's IV24 to capture the frames from tape as shown in illustration #1. Black and white is adequate for rotoscope reference. If you have numbered your frames sequentially, they can be batch loaded from DPaint's Picture Load menu then later saved as an Anim. Create a line drawing directly on each image as shown in #2 using a bright color not present in the photos. Next, using the Stencil feature, lock the line color then clear all frames to leave clean outline drawings as in #3. Use Fill and Draw tools to color the character. As described for the flapping wings, you can use a few of the backswing frames to create the faster striking swing. Saved as an animbrush, this sequence will eventually be added to a background as shown in #4.
Before adding the character to the background, create the sculpture. Draw, scan or digitize both a finished sculpture and a raw block of stone. Next calculate how many hammer blows you will use to complete the sculpture. This may be dictated by the desired run-time of the sequence. As a simple example, if you want 10 seconds of animation at 15 frames per second and there are 15 frames in one hammer cycle, you need 10 hammer cycles. You need one modification of the block for each hammer cycle with the final modification being the finished sculpture. An easy way to do this is to morph the block of stone into the sculpture. You could use any of the specialized morphing programs, but you may find that DPaint's own brush morphing capabilities are adequate for this project as long as both objects have distinctly different shapes. Pick up the stone block as a brush and hit "Alt-n" to move it to the "spare brush" buffer then pick up the sculpture as the second brush. Hit "Alt-m" for the morph requester. Enter the total number of desired cels (in our example enter 10, one for each hammer cycle). The computer now acts as your assistant and creates a 10 cel animbrush from your 2 key frames.
Set up a new animation with just your background image. It should have the same number of frames as there are cels in the sculpture morph (10 in our example). Stamp the sculpture morph animbrush into the scene to create a 10 frame animation. Next, modify that animation to accommodate the repeating 15 frame animbrush of the hammer cycle. To do this, add 14 frames to each of the 10 frames of the sculpture animation. Now place the hammer cycle animbrush in the scene so that the chisel appears to strike the block of stone. You could use DPaint's Move requester with all settings at zero to stamp the animbrush in place over all 150 frames. Playing the animation, the sculpture changes a little at each blow of the hammer until it is complete. As a final touch, add a little spray of dust with the airbrush tool for two frames each time a blow is struck. A translucent shadow helps fix the figure and sculpture to the ground. This visually complex ten second animation only required 12 original frames, 10 hammer swings and two sculpture key frames. Variations on this idea could be used to reveal rendered 3-D logos and titles.
Developing a clear methodology is critical to becoming a skilled animator.
You can increase your productivity if you learn to analyze a project at
the outset. Look for innovative ways to use cyclic motion and devise your
own techniques for stretching animation mileage without sacrificing visual
interest or quality.
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