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Computer facial animation is primarily an area of
computer graphics Computer graphics deals with generating images with the aid of computers. Today, computer graphics is a core technology in digital photography, film, video games, cell phone and computer displays, and many specialized applications. A great de ...
that encapsulates methods and techniques for generating and animating images or models of a character face. The character can be a
human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
, a humanoid, an
animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...
, a
legendary creature A legendary creature (also mythical or mythological creature) is a type of fictional entity, typically a hybrid, that has not been proven and that is described in folklore Folklore is shared by a particular group of people; it encompasses ...
or character, etc. Due to its subject and output type, it is also related to many other scientific and artistic fields from
psychology Psychology is the scientific study of mind and behavior. Psychology includes the study of conscious and unconscious phenomena, including feelings and thoughts. It is an academic discipline of immense scope, crossing the boundaries betwe ...
to traditional
animation Animation is a method by which image, still figures are manipulated to appear as Motion picture, moving images. In traditional animation, images are drawn or painted by hand on transparent cel, celluloid sheets to be photographed and exhibited ...
. The importance of
human faces The face is the front of an animal's head that features the eyes, nose and mouth, and through which animals express many of their emotions. The face is crucial for human identity, and damage such as scarring or developmental deformities may aff ...
in verbal and non-verbal communication and advances in computer graphics hardware and
software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...
have caused considerable scientific, technological, and artistic interests in computer facial animation. Although development of
computer graphics Computer graphics deals with generating images with the aid of computers. Today, computer graphics is a core technology in digital photography, film, video games, cell phone and computer displays, and many specialized applications. A great de ...
methods for facial animation started in the early-1970s, major achievements in this field are more recent and happened since the late 1980s. The body of work around computer facial animation can be divided into two main areas: techniques to generate animation data, and methods to apply such data to a character. Techniques such as
motion capture Motion capture (sometimes referred as mo-cap or mocap, for short) is the process of recording the movement of objects or people. It is used in military, entertainment, sports, medical applications, and for validation of computer vision and robo ...
and
keyframing In animation and filmmaking, a key frame (or keyframe) is a drawing or shot that defines the starting and ending points of a smooth transition. These are called ''frames'' because their position in time is measured in frames on a strip of fil ...
belong to the first group, while morph targets animation (more commonly known as blendshape animation) and
skeletal animation Skeletal animation or rigging is a technique in computer animation in which a character (or other articulated object) is represented in two parts: a surface representation used to draw the character (called the ''mesh'' or ''skin'') and a hierarc ...
belong to the second. Facial animation has become well-known and popular through animated feature
film A film also called a movie, motion picture, moving picture, picture, photoplay or (slang) flick is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, feelings, beauty, or atmosphere ...
s and computer games but its applications include many more areas such as
communication Communication (from la, communicare, meaning "to share" or "to be in relation with") is usually defined as the transmission of information. The term may also refer to the message communicated through such transmissions or the field of inquir ...
,
education Education is a purposeful activity directed at achieving certain aims, such as transmitting knowledge or fostering skills and character traits. These aims may include the development of understanding, rationality, kindness, and honesty. Va ...
, scientific
simulation A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of Conceptual model, models; the model represents the key characteristics or behaviors of the selected system or proc ...
, and
agent Agent may refer to: Espionage, investigation, and law *, spies or intelligence officers * Law of agency, laws involving a person authorized to act on behalf of another ** Agent of record, a person with a contractual agreement with an insuranc ...
-based systems (for example online customer service representatives). With the recent advancements in computational power in personal and
mobile devices A mobile device (or handheld computer) is a computer small enough to hold and operate in the hand. Mobile devices typically have a flat LCD or OLED screen, a touchscreen interface, and digital or physical buttons. They may also have a physical ...
, facial animation has transitioned from appearing in pre-rendered content to being created at runtime.


History

Human
facial expression A facial expression is one or more motions or positions of the muscles beneath the skin of the face. According to one set of controversial theories, these movements convey the emotional state of an individual to observers. Facial expressions are a ...
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 John Bulwer (baptised 16 May 1606 – buried 16 October 1656 ) was an English physician and early Baconian natural philosopher who wrote five works exploring the Body and human communication, particularly by gesture. He was the first person ...
in the late 1640s,
Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended fr ...
’s book ''The Expression of the Emotions in Men and Animals'' can be considered a major departure for modern research in behavioural
biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...
. Computer based facial expression modelling and
animation Animation is a method by which image, still figures are manipulated to appear as Motion picture, moving images. In traditional animation, images are drawn or painted by hand on transparent cel, celluloid sheets to be photographed and exhibited ...
is not a new endeavour. 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. in 1974, Parke developed a parameterized three-dimensional facial model. One of the most important attempts to describe facial movements was
Facial Action Coding System 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 Ek ...
(FACS). Originally developed by Carl-Herman Hjortsjö in the 1960s and updated by Ekman and
Friesen Friesen (; gsw-FR, Friese) is a commune in the Haut-Rhin department in Alsace in north-eastern France. See also * Communes of the Haut-Rhin département The following is a list of the 366 communes of the French department of Haut-Rhin. T ...
in 1978, FACS defines 46 basic facial Action Units (AUs). A major group of these Action Units represent primitive movements of facial muscles in actions such as raising brows, winking, and talking. Eight AU's 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. 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 animated short film ''
Tony de Peltrie Tony de Peltrie is a Canadian computer-animated short film from 1985. The short shows the first animated human character to express emotion through facial expressions and body movements, which touched the feelings of the audience.Philippe Bergeron ...
'' was a landmark for facial animation. This marked 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 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 ''Toy Story'' is a 1995 American computer-animated comedy film directed by John Lasseter (in his feature directorial debut), produced by Pixar Animation Studios and released by Walt Disney Pictures. The first installment in the '' Toy Story ...
'' (1995), ''
Antz ''Antz'' is a 1998 American computer-animated adventure comedy film produced by DreamWorks Animation (in its debut film) and Pacific Data Images and released by DreamWorks Pictures. It was directed by Eric Darnell and Tim Johnson (in their fe ...
'' (1998), ''
Shrek ''Shrek'' is a 2001 American computer-animated comedy film loosely based on the 1990 book of the same name by William Steig. It is the first installment in the ''Shrek'' franchise. The film was directed by Andrew Adamson and Vicky Jenso ...
'', and ''
Monsters, Inc. ''Monsters, Inc.'' (also known as ''Monsters, Incorporated'') is a 2001 American computer-animated Monster movie, monster comedy film produced by Pixar, Pixar Animation Studios for Walt Disney Pictures. Featuring the voices of John Goodman, B ...
'' (both 2001), and computer games such as ''
Sims Sims, sims or SIMS may refer to: Games * ''The Sims'', a life simulation video game series ** ''The Sims'' (video game), the first installment, released in 2000 ** ''The Sims 2'', the second installment, released in 2004 ** '' The Sims 3'', th ...
''. ''
Casper Casper may refer to: People * Casper (given name) * Casper (surname) * Casper (Maya ruler) (422–487?), ruler of the Mayan city of Palenque * Tok Casper, first known king of Maya city-state Quiriguá in Guatemala, ruling beginning in 426 * David ...
'' (1995), a milestone in this decade, was the first movie in which a lead actor was produced exclusively using digital facial animation. The sophistication of the films increased after 2000. In ''
The Matrix Reloaded ''The Matrix Reloaded'' is a 2003 American science-fiction action film written and directed by the Wachowskis. It is a sequel to ''The Matrix'' (1999) and the second installment in the ''Matrix'' film series. The film stars Keanu Reeves, Laure ...
'' and ''
The Matrix Revolutions ''The Matrix Revolutions'' is a 2003 American science fiction action film written and directed by the Wachowskis. It is the third installment in ''The Matrix'' film series, released six months following ''The Matrix Reloaded''. The film stars ...
'', dense
optical flow Optical flow or optic flow is the pattern of apparent motion of objects, surfaces, and edges in a visual scene caused by the relative motion between an observer and a scene. Optical flow can also be defined as the distribution of apparent veloci ...
from several high-definition cameras was used to capture realistic facial movement at every point on the face. '' Polar Express (film)'' used a large Vicon system to capture upward of 150 points. Although these systems are automated, a large amount of manual clean-up effort is still needed to make the data usable. Another milestone in facial animation was reached by ''
The Lord of the Rings ''The Lord of the Rings'' is an epic high-fantasy novel by English author and scholar J. R. R. Tolkien. Set in Middle-earth, intended to be Earth at some time in the distant past, the story began as a sequel to Tolkien's 1937 children's boo ...
'', where a character specific shape base system was developed. Mark Sagar pioneered the use of FACS in entertainment facial animation, and FACS based systems developed by Sagar were used on '' Monster House'', ''
King Kong King Kong is a fictional giant monster resembling a gorilla, who has appeared in various media since 1933. He has been dubbed The Eighth Wonder of the World, a phrase commonly used within the franchise. His first appearance was in the novelizat ...
'', and other films.


Techniques


Generating facial animation data

The generation of facial animation data can be approached in different ways: 1.) marker-based motion capture on points or marks on the face of a performer, 2.) markerless motion capture techniques using different type of cameras, 3.) audio-driven techniques, and 4.)
keyframe In animation and filmmaking, a key frame (or keyframe) is a drawing or shot that defines the starting and ending points of a smooth transition. These are called ''frames'' because their position in time is measured in frames on a strip of fil ...
animation. *
Motion capture Motion capture (sometimes referred as mo-cap or mocap, for short) is the process of recording the movement of objects or people. It is used in military, entertainment, sports, medical applications, and for validation of computer vision and robo ...
uses cameras placed around a subject. The subject is generally fitted either with reflectors (passive motion capture) or sources (active motion capture) that precisely determine the subject's position in space. The data recorded by the cameras is then digitized and converted into a three-dimensional computer model of the subject. Until recently, the size of the detectors/sources used by motion capture systems made the technology inappropriate for facial capture. However, miniaturization and other advancements have made motion capture a viable tool for computer facial animation.
Facial motion capture Facial motion capture is the process of electronically converting the movements of a person's face into a digital database using cameras or laser scanners. This database may then be used to produce computer graphics (CG), computer animation for mo ...
was used extensively in
Polar Express ''The Polar Express'' is a children's book written and illustrated by Chris Van Allsburg and published by Houghton Mifflin in 1985. The book is now widely considered to be a classic Christmas story for young children. It was praised for its detai ...
by
Imageworks Imageworks may refer to: * Sony Pictures Imageworks, a visual effects and character animation company headquartered in Vancouver, British Columbia, Canada * Image Works, a video game publisher in the late-1980s and early-1990s * ImageWorks (Disney) ...
where hundreds of motion points were captured. This film was very accomplished and while it attempted to recreate realism, it was criticized for having fallen in the '
uncanny valley In aesthetics, the uncanny valley ( ja, 不気味の谷 ''bukimi no tani'') is a hypothesized relation between an object's degree of resemblance to a human being and the emotional response to the object. The concept suggests that humanoid object ...
', the realm where animation realism is sufficient for human recognition and to convey the emotional message but where the characters fail to be perceived as realistic. The main difficulties of motion capture are the quality of the data which may include vibration as well as the retargeting of the geometry of the points. * Markerless motion capture aims at simplifying the motion capture process by avoiding encumbering the performer with markers. Several techniques came out recently leveraging different sensors, among which standard video cameras, Kinect and depth sensors or other structured-light based devices. Systems based on
structured light A structured light pattern designed for surface inspection An Automatix Seamtracker arc welding robot equipped with a camera and structured laser light source, enabling the robot to follow a welding seam automatically Structured light is the p ...
may achieve real-time performance without the use of any markers using a high speed structured light scanner. The system is based on a robust offline face tracking stage which trains the system with different facial expressions. The matched sequences are used to build a person-specific linear face model that is subsequently used for online face tracking and expression transfer. * Audio-driven techniques are particularly well fitted for speech animation. Speech is usually treated in a different way to the animation of facial expressions, this is because simple
keyframe In animation and filmmaking, a key frame (or keyframe) is a drawing or shot that defines the starting and ending points of a smooth transition. These are called ''frames'' because their position in time is measured in frames on a strip of fil ...
-based approaches to animation typically provide a poor approximation to real speech dynamics. Often
viseme A viseme is any of several speech sounds that look the same, for example when lip reading (Fisher 1968). Visemes and phonemes do not share a one-to-one correspondence. Often several phonemes correspond to a single viseme, as several phonemes look ...
s are used to represent the key poses in observed speech (i.e. the position of the lips, jaw and tongue when producing a particular
phoneme In phonology and linguistics, a phoneme () is a unit of sound that can distinguish one word from another in a particular language. For example, in most dialects of English, with the notable exception of the West Midlands and the north-west o ...
), however there is a great deal of variation in the realisation of visemes during the production of natural speech. The source of this variation is termed
coarticulation Coarticulation in its general sense refers to a situation in which a conceptually isolated speech sound is influenced by, and becomes more like, a preceding or following speech sound. There are two types of coarticulation: ''anticipatory coarticulat ...
which is the influence of surrounding visemes upon the current viseme (i.e. the effect of context). To account for coarticulation current systems either explicitly take into account context when blending viseme keyframes or use longer units such as
diphone In phonetics, a diphone is an adjacent pair of phones in an utterance. For example, in aɪfəʊn the diphones are a ɪ f ə ʊ n The term is usually used to refer to a recording of the transition between two phones. In the following d ...
,
triphone In linguistics, a triphone is a sequence of three consecutive phonemes. Triphones are useful in models of natural language processing where they are used to establish the various contexts in which a phoneme can occur in a particular natural languag ...
,
syllable A syllable is a unit of organization for a sequence of speech sounds typically made up of a syllable nucleus (most often a vowel) with optional initial and final margins (typically, consonants). Syllables are often considered the phonological "bu ...
or even
word A word is a basic element of language that carries an semantics, objective or pragmatics, practical semantics, meaning, can be used on its own, and is uninterruptible. Despite the fact that language speakers often have an intuitive grasp of w ...
and sentence-length units. One of the most common approaches to speech animation is the use of dominance functions introduced by Cohen and Massaro. Each dominance function represents the influence over time that a viseme has on a speech utterance. Typically the influence will be greatest at the center of the viseme and will degrade with distance from the viseme center. Dominance functions are blended together to generate a speech trajectory in much the same way that spline basis functions are blended together to generate a curve. The shape of each dominance function will be different according to both which viseme it represents and what aspect of the face is being controlled (e.g. lip width, jaw rotation etc.). This approach to computer-generated speech animation can be seen in the Baldi talking head. Other models of speech use basis units which include context (e.g.
diphone In phonetics, a diphone is an adjacent pair of phones in an utterance. For example, in aɪfəʊn the diphones are a ɪ f ə ʊ n The term is usually used to refer to a recording of the transition between two phones. In the following d ...
s,
triphone In linguistics, a triphone is a sequence of three consecutive phonemes. Triphones are useful in models of natural language processing where they are used to establish the various contexts in which a phoneme can occur in a particular natural languag ...
s etc.) instead of visemes. As the basis units already incorporate the variation of each viseme according to context and to some degree the dynamics of each viseme, no model of
coarticulation Coarticulation in its general sense refers to a situation in which a conceptually isolated speech sound is influenced by, and becomes more like, a preceding or following speech sound. There are two types of coarticulation: ''anticipatory coarticulat ...
is required. Speech is simply generated by selecting appropriate units from a database and blending the units together. This is similar to concatenative techniques in audio
speech synthesis Speech synthesis is the artificial production of human speech. A computer system used for this purpose is called a speech synthesizer, and can be implemented in software or hardware products. A text-to-speech (TTS) system converts normal languag ...
. The disadvantage to these models is that a large amount of captured data is required to produce natural results, and whilst longer units produce more natural results the size of database required expands with the average length of each unit. Finally, some models directly generate speech animations from audio. These systems typically use
hidden Markov model A hidden Markov model (HMM) is a statistical Markov model in which the system being modeled is assumed to be a Markov process — call it X — with unobservable ("''hidden''") states. As part of the definition, HMM requires that there be an ob ...
s or
neural net Artificial neural networks (ANNs), usually simply called neural networks (NNs) or neural nets, are computing systems inspired by the biological neural networks that constitute animal brains. An ANN is based on a collection of connected unit ...
s to transform audio parameters into a stream of control parameters for a facial model. The advantage of this method is the capability of voice context handling, the natural rhythm, tempo, emotional and dynamics handling without complex approximation algorithms. The training database is not needed to be labeled since there are no phonemes or visemes needed; the only needed data is the voice and the animation parameters. *
Keyframe In animation and filmmaking, a key frame (or keyframe) is a drawing or shot that defines the starting and ending points of a smooth transition. These are called ''frames'' because their position in time is measured in frames on a strip of fil ...
animation is the least automated of the processes to create animation data although it delivers the maximum amount of control over the animation. It is often used in combination with other techniques to deliver the final polish to the animation. The
keyframe In animation and filmmaking, a key frame (or keyframe) is a drawing or shot that defines the starting and ending points of a smooth transition. These are called ''frames'' because their position in time is measured in frames on a strip of fil ...
data can be made of scalar values defining the morph targets coefficients or rotation and translation values of the bones in models with a bone based rig. Often to speed up the
keyframe In animation and filmmaking, a key frame (or keyframe) is a drawing or shot that defines the starting and ending points of a smooth transition. These are called ''frames'' because their position in time is measured in frames on a strip of fil ...
animation process a control rig is used by the animation. The control rig represents a higher level of abstraction that can act on multiple morph targets coefficients or bones at the same time. For example, a "smile" control can act simultaneously on the mouth shape curving up and the eyes squinting.


Applying facial animation to a character

The main techniques used to apply facial animation to a character are: 1.) morph targets animation, 2.) bone driven animation, 3.) texture-based animation (2D or 3D), and 4.)
physiological Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...
models. *
Morph target Morph target animation, per-vertex animation, shape interpolation, shape keys, or blend shapes is a method of 3D computer animation used together with techniques such as skeletal animation. In a morph target animation, a "deformed" version of a m ...
s (also called "blendshapes") based systems offer a fast playback as well as a high degree of fidelity of expressions. The technique involves modeling portions of the face mesh to approximate expressions and
viseme A viseme is any of several speech sounds that look the same, for example when lip reading (Fisher 1968). Visemes and phonemes do not share a one-to-one correspondence. Often several phonemes correspond to a single viseme, as several phonemes look ...
s and then blending the different sub meshes, known as morph targets or blendshapes. Perhaps the most accomplished character using this technique was Gollum, from ''The Lord of the Rings''. Drawbacks of this technique are that they involve intensive manual labor and are specific to each character. Recently, new concepts in 3D modeling have started to emerge. Recently, a new technology departing from the traditional techniques starts to emerge, such as ''
Curve Controlled Modeling In mathematics, a curve (also called a curved line in older texts) is an object similar to a line, but that does not have to be straight. Intuitively, a curve may be thought of as the trace left by a moving point. This is the definition that a ...
'' that emphasizes the modeling of the movement of a 3D object instead of the traditional modeling of the static shape. * Bone driven animation is very broadly used in games. The bones setup can vary between few bones to close to a hundred to allow all subtle facial expressions. The main advantages of bone driven animation is that the same animation can be used for different characters as long as the morphology of their faces is similar, and secondly they do not require loading in memory all the
Morph target Morph target animation, per-vertex animation, shape interpolation, shape keys, or blend shapes is a method of 3D computer animation used together with techniques such as skeletal animation. In a morph target animation, a "deformed" version of a m ...
s data. Bone driven animation is most widely supported by 3D game engines. Bone driven animation can be used for both 2D and 3D animation. For example, it is possible to rig and animate using bones a 2D character using
Adobe Flash Adobe Flash (formerly Macromedia Flash and FutureSplash) is a multimedia Computing platform, software platform used for production of Flash animation, animations, rich web applications, application software, desktop applications, mobile apps, mo ...
. * Texture-based animation uses pixel color to create the animation on the character face. 2D facial animation is commonly based upon the transformation of images, including both images from still photography and sequences of video. Image
morphing Morphing is a special effect in motion pictures and animations that changes (or morphs) one image or shape into another through a seamless transition. Traditionally such a depiction would be achieved through dissolving techniques on film. Since ...
is a technique which allows in-between transitional images to be generated between a pair of target still images or between frames from sequences of video. These
morphing Morphing is a special effect in motion pictures and animations that changes (or morphs) one image or shape into another through a seamless transition. Traditionally such a depiction would be achieved through dissolving techniques on film. Since ...
techniques usually consist of a combination of a geometric deformation technique, which aligns the target images, and a cross-fade which creates the smooth transition in the image texture. An early example of image
morphing Morphing is a special effect in motion pictures and animations that changes (or morphs) one image or shape into another through a seamless transition. Traditionally such a depiction would be achieved through dissolving techniques on film. Since ...
can be seen in
Michael Jackson Michael Joseph Jackson (August 29, 1958 – June 25, 2009) was an American singer, songwriter, dancer, and philanthropist. Dubbed the "King of Pop", he is regarded as one of the most significant cultural figures of the 20th century. Over a ...
's video for "Black Or White". In 3D animation texture based animation can be achieved by animating the texture itself or the UV mapping. In the latter case a texture map of all the facial expression is created and the UV map animation is used to transition from one expression to the next. *
Physiological Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...
models, such as skeletal muscle systems and physically based head models, form another approach in modeling the
head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may ...
and
face The face is the front of an animal's head that features the eyes, nose and mouth, and through which animals express many of their emotions. The face is crucial for human identity, and damage such as scarring or developmental deformities may aff ...
. Here, the physical and
anatomical Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having it ...
characteristics of
bone A bone is a Stiffness, rigid Organ (biology), organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red blood cell, red and white blood cells, store minerals, provid ...
s, tissues, and
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...
are simulated to provide a realistic appearance (e.g. spring-like elasticity). Such methods can be very powerful for creating realism but the complexity of facial structures make them computationally expensive, and difficult to create. Considering the effectiveness of parameterized models for communicative purposes (as explained in the next section), it may be argued that physically based models are not a very efficient choice in many applications. This does not deny the advantages of physically based models and the fact that they can even be used within the context of parameterized models to provide local details when needed.


Face animation languages

Many face animation languages are used to describe the content of facial animation. They can be input to a compatible "player"
software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...
which then creates the requested actions. Face animation languages are closely related to other
multimedia Multimedia is a form of communication that uses a combination of different content forms such as text, audio, images, animations, or video into a single interactive presentation, in contrast to tradition ...
presentation languages such as SMIL and
VRML VRML (Virtual Reality Modeling Language, pronounced ''vermal'' or by its initials, originally—before 1995—known as the Virtual Reality Markup Language) is a standard file format for representing 3-dimensional (3D) interactive vector graphi ...
. Due to the popularity and effectiveness of
XML Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable ...
as a data representation mechanism, most face animation languages are XML-based. For instance, this is a sample from
Virtual Human Markup Language The Virtual Human Markup Language often abbreviated as VHML is a markup language used for the computer animation of human bodies and facial expressions.''Data-driven 3D facial animation'' by Zhigang Deng, Ulrich Neumann 2007 page 54 The language ...
(VHML): First I speak with an angry voice and look very angry, but suddenly I change to look more surprised. More advanced languages allow decision-making, event handling, and parallel and sequential actions. The ''Face Modeling Language'' (FML) is an
XML Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable ...
-based language for describing face
animation Animation is a method by which image, still figures are manipulated to appear as Motion picture, moving images. In traditional animation, images are drawn or painted by hand on transparent cel, celluloid sheets to be photographed and exhibited ...
. FML supports
MPEG-4 MPEG-4 is a group of international standards for the compression of digital audio and visual data, multimedia systems, and file storage formats. It was originally introduced in late 1998 as a group of audio and video coding formats and related tec ...
Face Animation Parameter A Face Animation Parameter (FAP) is a component of the MPEG-4 Face and Body Animation (FBA) International Standard (ISO/IE14496-1 developed by the Moving Pictures Experts Group. It describes a standard for virtually representing humans and human ...
s (FAPS), decision-making and dynamic
event handling In programming and software design, an event is an action or occurrence recognized by software, often originating asynchronously from the external environment, that may be handled by the software. Computer events can be generated or triggere ...
, and typical programming constructs such as loops. It is part of the iFACE system. The following is an example from FML:


See also

*
Animation Animation is a method by which image, still figures are manipulated to appear as Motion picture, moving images. In traditional animation, images are drawn or painted by hand on transparent cel, celluloid sheets to be photographed and exhibited ...
*
Caricature A caricature is a rendered image showing the features of its subject in a simplified or exaggerated way through sketching, pencil strokes, or other artistic drawings (compare to: cartoon). Caricatures can be either insulting or complimentary, a ...
*
Computer animation Computer animation is the process used for digitally generating animations. The more general term computer-generated imagery (CGI) encompasses both static scenes (still images) and dynamic images (moving images), while computer animation refe ...
*
Computer graphics Computer graphics deals with generating images with the aid of computers. Today, computer graphics is a core technology in digital photography, film, video games, cell phone and computer displays, and many specialized applications. A great de ...
*
Deepfake Deepfakes (a portmanteau of "deep learning" and "fake") are synthetic media in which a person in an existing image or video is replaced with someone else's likeness. While the act of creating fake content is not new, deepfakes leverage powerful ...
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Facial expression A facial expression is one or more motions or positions of the muscles beneath the skin of the face. According to one set of controversial theories, these movements convey the emotional state of an individual to observers. Facial expressions are a ...
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Facial motion capture Facial motion capture is the process of electronically converting the movements of a person's face into a digital database using cameras or laser scanners. This database may then be used to produce computer graphics (CG), computer animation for mo ...
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Interactive online characters An intelligent virtual assistant (IVA) or intelligent personal assistant (IPA) is a software agent that can perform tasks or services for an individual based on commands or questions. The term "chatbot" is sometimes used to refer to virtual ...
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Morphing Morphing is a special effect in motion pictures and animations that changes (or morphs) one image or shape into another through a seamless transition. Traditionally such a depiction would be achieved through dissolving techniques on film. Since ...
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Parametric surface A parametric surface is a surface in the Euclidean space \R^3 which is defined by a parametric equation with two parameters Parametric representation is a very general way to specify a surface, as well as implicit representation. Surfaces that oc ...
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Texture mapping Texture mapping is a method for mapping a texture on a computer-generated graphic. Texture here can be high frequency detail, surface texture, or color. History The original technique was pioneered by Edwin Catmull in 1974. Texture mapping ...


References


Further reading

* ''Computer Facial Animation'' by Frederic I. Parke, Keith Waters 2008 * ''Data-driven 3D facial animation'' by Zhigang Deng, Ulrich Neumann 2007 * ''Handbook of Virtual Humans'' by Nadia Magnenat-Thalmann and Daniel Thalmann, 2004 * {{cite book, last=Osipa, first=Jason, title=Stop Staring: Facial Modeling and Animation Done Right, publisher=John Wiley & Sons, year=2005, edition=2nd, isbn=978-0-471-78920-8, url=https://www.amazon.co.uk/gp/reader/0471789208/ref=sib_dp_pt#reader-link


External links


Face/Off: Live Facial Puppetry - Realtime markerless facial animation technology developed at ETH ZurichThe "Artificial Actors" Project - Institute of AnimationiFACEAnimated Baldi
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Carl-Herman Hjortsjö, Man's face and mimic language"
(the original Swedish title of the book is: "Människans ansikte och mimiska språket". The correct translation would be: "Man's face and facial language") Computer animation Anatomical simulation