Abstract Muscle Action Procedures
for Human Face Animation
N. Magnenat-Thalmann, E. Primeau, and D. Thalmann
Visual Computer, 1988
Abstract
A new way of controlling human face animation and synchronizing speech
is proposed. It is based on the concept of abstract muscle action
procedure (AMA procedure). An AMA procedure is a specialized procedure
which simulates the specific action of a face muscle. This paper
describes the new technique and presents a methodology for animating
the face of synthetic actors based on three levels: the AMA procedure
level, the expression level, and the script level. The role of
multiple tracks is also emphasized. Practical examples are also
explained in detail, based on the film Rendez-vous a Montreal
with the synthetic actors Marilyn Monroe and Humphrey Bogart.
Summary
Muscle actions are simulated with abstract muscle action procedures.
Each AMA procedure corresponds roughly to a muscle or bone structure.
AMA procedures are not independent of each other, so the order of
action is relevant. As human muscles are highly complex, the AMA
procedures must simulate the same motion without imitating the
complexity. The following is a list of the most important AMA
procedures:
Number | AMA Procedure | Range |
1 | Vertical_Jaw | 0 to 1 |
2 | Close_Upper_Lip | 0 to 1 |
3 | Close_Lower_Lip | 0 to 1 |
4 | Compressed_Lip | 0 to 1 |
6 | Mouth_Beak | 0 to 1 |
7 | Right_Eyelid | -1 to 1 |
8 | Left_Eyelid | -1 to 1 |
9 | Left_Lip_Raiser | 0 to 1 |
10 | Right_Lip_Raiser | 0 to 1 |
11 | Left_Zygomatic | 0 to 1 |
12 | Right_Zygomatic | 0 to 1 |
23 | Move_Right_Eye_Horizontal | -1 to 1 |
24 | Move_Right_Eye_Vertical | -1 to 1 |
25 | Move_Left_Eye_Horizontal | -1 to 1 |
26 | Move_Left_Eye_Vertical | -1 to 1 |
27 | Right_Risorius | 0 to 1 |
28 | Left_Risorius | 0 to 1 |
29 | Move_Right_Eyebrow | -1 to 1 |
30 | Move_Left_Eyebrow | -1 to 1 |
It is possible to animate a human face by manipulating the facial
parameters using AMA procedures. However, these procedures should be
considered low-level access. By combining the facial parameters
obtained by the AMA procedures in different ways, we can construct
more complex entities corresponding to the well-known concept of
facial expression.