Жүздік қозғалыстарды жіктеу жүйесі

System of classifying human facial movements

The Facial Action Coding System (FACS) is a system to taxonomize human facial movements by their appearance on the face, based on a system originally developed by a Swedish anatomist named Carl Herman Hjortsjö. It was later adopted by Paul Ekman and Wallace V. Friesen, and published in 1978. Ekman, Friesen, and Joseph C. Hager published a significant update to FACS in 2002. Movements of individual facial muscles are encoded by the FACS from slight different instant changes in facial appearance. It has proven useful to psychologists and to animators.

In 2009, a study was conducted to study spontaneous facial expressions in sighted and blind judo athletes. They discovered that many facial expressions are innate and not visually learned.

The use of the FACS has been proposed for use in the analysis of depression, and the measurement of pain in patients unable to express themselves verbally.

FACS coding is also used extensively in computer animation, with facial expressions being expressed as vector graphics of AUs. FACS vectors are used as weights for blendshapes corresponding to each AU, with the resulting face mesh then being used to render the finished face. Deep learning techniques can be used to determine the FACS vectors from face images obtained during motion capture acting or other performances.

For clarification, the FACS is an index of facial expressions, but does not actually provide any bio mechanical information about the degree of muscle activation. Though muscle activation is not part of the FACS, the main muscles involved in the facial expression have been added here. Action units (AUs) are the fundamental actions of individual muscles or groups of muscles. Action descriptors (ADs) are unitary movements that may involve the actions of several muscle groups (e. g., a forward‐thrusting movement of the jaw). The muscular basis for these actions has not been specified and specific behaviors have not been distinguished as precisely as for the AUs. For the most accurate annotation, the FACS suggests agreement from at least two independent certified FACS encoders.

There are other modifiers present in FACS codes for emotional expressions, such as "R" which represents an action that occurs on the right side of the face and "L" for actions which occur on the left. An action which is unilateral (occurs on only one side of the face) but has no specific side is indicated with a "U" and an action which is bilateral but has a stronger side is indicated with an "A" for asymmetric.

AU number FACS name Action 51 Head turn left 52 Head turn right 53 Head up 54 Head down 55 Head tilt left M55 Head tilt left The onset of the symmetrical 14 is immediately preceded or accompanied by a head tilt to the left. 56 Head tilt right M56 Head tilt right The onset of the symmetrical 14 is immediately preceded or accompanied by a head tilt to the right. 57 Head forward M57 Head thrust forward The onset of 17+24 is immediately preceded, accompanied, or followed by a head thrust forward. 58 Head back M59 Head shake up and down The onset of 17+24 is immediately preceded, accompanied, or followed by an up down head shake (nod). M60 Head shake side to side The onset of 17+24 is immediately preceded, accompanied, or followed by a side to side head shake. M83 Head upward and to the side The onset of the symmetrical 14 is immediately preceded or accompanied by a movement of the head, upward and turned or tilted to either the left or right.

AU number FACS name Action 61 Eyes turn left M61 Eyes left The onset of the symmetrical 14 is immediately preceded or accompanied by eye movement to the left. 62 Eyes turn right M62 Eyes right The onset of the symmetrical 14 is immediately preceded or accompanied by eye movement to the right. 63 Eyes up 64 Eyes down 65 Walleye 66 Cross eye M68 Upward rolling of eyes The onset of the symmetrical 14 is immediately preceded or accompanied by an upward rolling of the eyes. 69 Eyes positioned to look at other person The 4, 5, or 7, alone or in combination, occurs while the eye position is fixed on the other person in the conversation. M69 Head or eyes look at other person The onset of the symmetrical 14 or AUs 4, 5, and 7, alone or in combination, is immediately preceded or accompanied by a movement of the eyes or of the head and eyes to look at the other person in the conversation.