Computer facial animation is primarily an area of computer graphics that encapsulates models and techniques for generating and animating images of the human head and face. Due to its subject and output type, it is also related to many other scientific and artistic fields from psychology to traditional animation. The importance of human faces in verbal and non-verbal communication and advances in computer graphics hardware and software have caused considerable scientific, technological, and artistic interests in computer facial animation.
Although development of computer graphics methods for facial animation started in the early 1970s, major achievements in this field are more recent and happened since the late 1980s.
Human facial expression has been the subject of scientific investigation for more than one hundred years. Study of facial movements and expressions started from a biological point of view. After some older investigations, for example by John Bulwer in late 1640s, Charles Darwin’s book The Expression of the Emotions in Men and Animals can be considered a major departure for modern research in behavioral biology.
More recently, one of the most important attempts to describe facial activities was Facial Action Coding System. Introduced by Ekman and Friesen in 1978, FACS defines 46 basic facial Action Units. A major group of these Action Units represent primitive movements of facial muscles in actions such as raising brows, winking, and talking. Eight AUs are for rigid three-dimensional head movements, i.e. turning and tilting left and right and going up, down, forward and backward. FACS has been successfully used for describing desired movements of synthetic faces and also in tracking facial activities.
Computer based facial expression modeling and animation is not a new endeavor. The earliest work with computer based facial representation was done in the early 1970s. The first three-dimensional facial animation was created by Parke in 1972. In 1973, Gillenson developed an interactive system to assemble and edit line drawn facial images. And in 1974, Parke developed a parameterized three-dimensional facial model.
The early 1980s saw the development of the first physically based muscle-controlled face model by Platt and the development of techniques for facial caricatures by Brennan. In 1985, the short animated film ``Tony de Peltrie’’ was a landmark for facial animation. In it for the first time computer facial expression and speech animation were a fundamental part of telling the story.
The late 1980s saw the development of a new muscle-based model by Waters, the development of an abstract muscle action model by Magnenat-Thalmann and colleagues, and approaches to automatic speech synchronization by Lewis and by Hill. The 1990s have seen increasing activity in the development of facial animation techniques and the use of computer facial animation as a key storytelling component as illustrated in animated films such as Toy Story, Antz, Shrek, and Monsters, Inc, and computer games such as Sims. Casper (1995) is a milestone in this period, being the first movie with a lead actor produced exclusively using digital facial animation (Toy Story was released later the same year).
Data Sourced from:Facial Expressions and Body Langauge
Using facial expressions on characters
Facial expressions are an essential part of character creations. Facial expressions allow your character to develop a personality. There are over 40 muscles in the human face and these muscles are used within humans to distinguish and show different emotions. Disney is an excellent example of animation character creations using animals. The animals that Disney often creates usually have very distinguishing humanistic facial features to show their expressions and to broadcast facial expressions to a young audience. Having humanistic facial features on any kind of character allows a better connection for any audience to connect with the character and to easily understand their emotions, wants and needs. This behaviour can be seen in very small children and especially babies. Babies are usually use sound as a form to connection to a mother but the mother can distinguish a babies wants and need mostly by facial features to tell whether a baby is sad, happy etc.
The Disney character Micky Mouse walks upright and his mannerisms are very human, this is also true for his facial expressions that more resemble a young boy than a mouse. This can be seen in the image below:
Facially he primarily tries to be more like a dog but because Pluto doesn't talk he needs to show off his emotions by changing the shape of his mouth and eyes which will also make him look more human, this is especially noticeable with his lips.
Why are facial expressions important?
The face as a whole indicates much about human moods as well. Specific emotional states, such as happiness or sadness, are expressed through a smile or a frown, respectively. There are seven universally recognized emotions shown through facial expressions: fear, anger, surprise, contempt, disgust, happiness, and sadness. Regardless of culture, these expressions are the same. However, the same emotion from a specific facial expression may be recognized by a culture, but the same intensity of emotion may not be perceived. Here Hilary Freeman quotes in her article from the guardian:
“Non-verbal factors, such as the tone of your voice, count for 38%. But visual factors such as facial expressions, gestures, pupil dilation etc., make up a massive 55% of your appearance rating”
Facial expressions are used to express a personals feels and moods. A painting is a prime example of the use of personal feelings and moods. A single image of a facial expression cannot build a personality however it can represent a characters mood and what they are feeling at that moment in time. We can use this technique to build a personality when we use video or create animation when using characters.
The concepts of the facial expressions include:
- a characteristic of a person that is represented, i.e., the signified;
- a visual configuration that represents this characteristic, i.e., the signifier;
- the physical basis of this appearance, or sign vehicle, e.g., the skin, muscle movements, fat, wrinkles, lines, blemishes, etc.; and
- typically, some person or other perceiver that perceives and interprets the signs.
Use of Body Language
Body language is used especially to express feelings; this is used both in everyday life and theatrical. For instance if we do not like someone, it is often difficult to say that directly to the person. However we can make it clear either intentionally or unintentionally through the use of our body language. The opposite is also true. We may say that we are angry through words yet our body language may say loudly and clearly that we are not. This can be very confusing for the person receiving our emotions such as somebody we are communication through, especially in performance and video. This is usually described as giving out double messages - one message in words and an opposite message in body language. It is also difficult to lie or cover up our feelings through body language. People may give their true feelings away by not being aware of their body language.
Darwin's Theories on Emotions
Darwin tried to extend his theories on evolutions of structures to behavior. He felt that behavior also evolves, and concluded from the universality of many facial expressions (sadness, happiness, etc.) that such behaviors also evolved from lower life forms.
His theory had three principles: 1. Facial expressions are "serviceable habits" that helped the organism react to sensations and internal states. 2. For many actions there are anti-thetical reactions caused by opposite stimulus conditions. 3. That acts like tears, trembling, and rage are caused by the nervous system.
These principles don't give us much clue as to how facial expressions are created.
Waynbaum's Theory on Emotional Expression
He noticed that 1. The blood supply of face and brain come from the same source (carotid artery). The cerebral blood supply must be stable. 3. The face has many, many muscles. especially around arteries. Why?
His theory is that emotional states cause changes in cerebral flow which cause disequilibrium. To bring the system back to equilibrium, the facial muscles constrict or increase facial blood flow by relaxing or contracting.
He also asserted that elation follows the smile, not the opposite. The blood flow changes caused by contracting the facial muscles in the smile alter cerebral blood flow and cause an emotional change. He extends this reasoning to account for all kinds of other bizarre facial habits associated with emotions -- wrinkled forheads, rubbing one's eyes, hand on forehead, pulling earlobes, licking lips, etc.