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Chapter 14
Facial Animation
Expressing
Emotion
Copyright 1999
Peter Ratner
(Excerpt from Mastering 3D Animation)
When animating
emotion, a reliance on only facial animation will have little substance
if it is not combined with the relevant posture of the body. The attitude
of the body should support the expression on the face (Figure 14-1,
14-2 and 14-3).
Figure 14-1
The downward slope of the shoulders, stooped torso, hanging arms and
dragging feet combined with a sad facial expression communicates depression.
Figure 14-2
Happiness is expressed through a combination of bright eyes, upturned
corners of the mouth, raised eyebrows, a lively stride, straight back,
and raised shoulders and arms.
Figure 14-3 A coy demeanor
can be displayed by biting down on the lower lip, casting eyes downward,
bending the neck and keeping the limbs close to the body.
Normally, the
facial expression will show up first, which is then followed by the
movement of the body. The two occurrences are only fractions of a second
apart, but nevertheless should be animated in that order. For example,
if the person perceives something, the eyes are the first to move, followed
by the turn of the head, then the shoulders and finally the rest of
the body.
Although
the posture of the body reflects the mood on the face, this discussion
will focus solely on the drama of facial expressions. One of the most
important aspects of facial animation is that the combination of various
head muscles convey emotion. Even though one has to model the various
expressions as single occurrences, it is the assemblage of these, during
the animation process, that yields the appropriate emotional state.
Most of the facial muscles, animated singly, bring about only a mild
drama.
The muscles
of the face are close to the skin and reciprocally connected. One has
only to close one eye and observe the upward movement in the corner
of the mouth to see this.
Most mid
to high-end software packages offer some kind of shape shifting tool
(Figure 14-4).
Figure 14-4 Modeling the various expressions
individually allows one the flexibility to combine them in numerous
ways. Many programs such as this one, use sliding buttons to blend the
various expressions.
These often
use sliding buttons which can generate various percentages of each facial
movement. If the eye, mouth, nose, eyebrows, jaw, and so on movements
are modeled separately, one can achieve a diversity of expressions and
phonetic shapes for speech. Since the muscles on the left and right
side of the face vary in strength, some of the features are modeled
as separate left and right shapes. When modeling the following expressions,
a hand held mirror becomes an indispensable tool.
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