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Chapter 11 Animation Composition
Complex and articulated systems of motion have many parts moving at different
speeds, in different arcs, and in different directions. Each component of the character
or system must be allowed to continue independent movement from the main body.
Secondary Action
A
secondary action,
or complementary action, is motion caused by the dominant
or primary action. Many secondary actions are part of the overlapping actions system,
but are not required to be part of that system. The addition of secondary action is
when things really start to come together for the animated movement.
Imagine a baseball player swinging at the ball. The primary action of swinging
the bat is animated following the principles of anticipation, squash and stretch, arcs,
and follow-through and overlapping action. But, what about the details outside of
that motion? The player’s uniform wrinkles, his hat spins, his teeth clench, dirt in the
batter’s box is moved around, and if the player makes contact, the ball travels away
from the bat. Each of these secondary actions helps complement the primary action.
If the player does not hit the ball, then the ball ends up in the catcher’s mitt, which
causes a whole different set of secondary actions to occur.
Animations of animals often involve secondary actions of the tail, fur, tongue,
and ears. Many animations of a dog, for example, have the tongue hanging
outside of the mouth to add a comical secondary action of a wet, flopping
tongue, as shown in Figure 11-11. The tongue bounces along in response to the
primary action of the dog, whether running, turning its head, or barking.
Slow In and Slow Out
Slow in
describes how motion
begins gradually, not at once.
Slow
out
describes how motion ends
gradually, not at once. In physics,
this principle is known as
inertia.
Due to inertia, objects take time to
start moving and to stop moving.
From a stop, a car does not instantly
move at 65 miles per hour, even if the driver presses the accelerator pedal to the floor.
The car slowly gains speed. When stopping, the car does not instantly reach a speed
of zero. Even with hard braking, the car will gradually come to a stop.
In an animation, increasing or decreasing the number of frames over which
a motion occurs adjusts the slow in and slow out. If the motion occurs over a
greater number of frames, the slow in or slow out is increased. If the motion
occurs over a fewer number of frames, the slow in or slow out is reduced.
CHEAT CODE: INERTIA
Inertia is a resistance to a change in
motion. This means that an object that
is stopped wants to stay stopped. An
object in motion wants to stay in motion.
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