You are here: UK Essays » Custom Essays » Animation Morphing Expressions

Free Essays - Essays

Animation Morphing Expressions

Literature Review

Animating and morphing three dimensional facial models and expressions has always been a complicated task for all graphical animators. [1] This chapter represents issues as well as the different aspects of facial animations; this will include the history behind facial expression animations and will also discuss the increasingly popular and commonly used software packages which enable one to successfully animate various facial expressions.

Together with, a brief summary of the current top five morphing applications that are available will be included; these will set the basic grounds for the morphing tool that is to be developed. In addition to this, the chapter will consist of the broad range of past research including the history, psychology, facial modelling and animation techniques. This background research has been conducted to make sure that a unique tool is designed and implemented which will benefit the users it is intended for.

The subsections within this chapter cover how facial expression animations are dealt with as well as its development over time. Section 1.1 consists of the background history behind computer facial animations which includes the historical review. Section 1.2 explains various psychological theories on facial animation.

Section 1.3 covers the current 3d modelling and animation packages that enable animators to model and animate facial expressions. This section will set the basis of the morphing tool that is to be designed using 3D Studio Max and Max Script. Section 1.4 covers the current morphing applications and plug-ins, to obtain a clear view for the design for the new morphing tool. The chapter ends with section 1.5 which discusses the different techniques for facial modelling and animating facial expressions.

The subsections covered in this chapter are:

1.1 Background History of Computer Facial Animation

1.2 Psychology and Expressions

1.3 Current 3D Modelling and Animation Packages

1.4 Current Morphing Applications

1.5 Facial Modelling & Animation Methods

1.1 Background History of Computer Facial Animation

“The human face - in repose and in movement, at the moment of death as in life, in silence and in speech, when seen or sensed from within, in actuality or as represented in art or recorded by the camera - is a commanding, complicated, and at times confusing source of information.” [P. Ekman, W. Friesen, and P. Ellsworth, Emotion in the Human Face, 1972, p. 1]

The human face is capable of performing a number of various facial expressions. [1] It has been exposed through previous studies that the movement of the three main facial regions the eyebrows, the eyes and the mouth have a vital and significant role in producing facial expressions. [2] [19], for example the expression happiness is known to be produced by the mouth, were as the expression confusion is portrayed by the movement of the eyebrows. [9]

The animation field has dramatically amplified over the past couple of years through huge amounts of effort in the advanced development of hardware and software, with the refined improvements in computer graphic algorithms. These developments and improvements in technology have significantly improved and made it possible to create facial animations and make them come alive to a certain extent. [25]

Computer Facial Animations dates back 37 years, when they first started to develop graphical effects and animations, but there have been significant improvements since the 1980s.

Modelling and animating facial expressions is not a new venture; as scientific investigators have been investigating on human facial animation for over a century. The starting point in researching and investigating facial animation was from a biological point of view. The 1970s saw the most primitive work in graphically based facial animations on computers. During the 1970s and in particular 1972, Professor Frederic I. Parke was part of the architecture and director of visualisation laboratory cited in Taxes, he was the first who created computerised three-dimensional head models. [1] [25]

The three-dimensional head models that Parke developed was used to produce three-dimensional points in the form of a mesh; controlled using two parameters, the expression parameter and the conformation parameter. [1] To compute facial actions one can make use of the expressions parameter as it can produce various actions for example, eyebrow stretching and closing the eyes. To control the features on the face one could make use of the conformation parameter as it can control the feature points on the face such as the eyes and lip corners. [25]

However, after a few years, Parke’s goal was to be able create animations rapidly with use of photogrammetric techniques that enabled him to gather 3D data from the face and create facial animations by interpolating between the various facial expressions [16]. In 1987 Keith Waters, currently the Director of Research at Orange Labs Boston MA, USA, developed a facial model based on muscles of the face. This facial model made it possible for one to create realistic facial expressions [1].

Generating complex facial expressions from a 3D face model has always been a difficult task. Especially when we try to create realistic facial expressions; [1] the reason behind this is that a fake expression can be easily noticed, for example the difference between a fake smile and a realistic smile is that a fake smile is a pretence smile which can be identified by features on the face such as the eyes. A realistic smile can be identified easily as it reflects in the eyes and the eyebrows.

In the past it was very difficult to produce faultless and realistic facial animations due to less computational power and not enough resources available. [1] One can identify real and unreal expressions on the human face through the shape and positions of various parts on the face, such as the eyebrows, eyes, nose and mouth as they pursue certain natural rules. [13] If these rules are violated then there would be unrealistic facial expressions.

However in recent years there has been significant amount of growth in producing realistic facial animations with the development and use of 3D scanners and photometric techniques that make it possible to digitise facial geometries and textures, this allows the animator to detain the face object rapidly. [12]. New animation systems have been developed which enable one by attaching tracking markers to a real human face and then deriving facial movements in three-dimensional space. A model was developed in 2003 by Martin Breidt which combined the use of three-dimensional scans and motion capture of data to produce exceedingly real facial animations. [3]

1.1.1 The Historical Review

Facial expression research has been around since the 19^th century. There were many researchers who studied the relationships and connections between facial movements, emotions and expressions. In 1872, Charles Darwin conducted observations on various facial expressions and carefully studied and recognised the characteristics of the different facial movements that appeared from the different expressions of different cultures. Charles Darwin stated that all cultures are the same and produce the same expressions. [1] [11].

Over the years, there have been many issues related to facial expressions that have been investigated, which involves how facial expressions, movements and emotions are produced and identified. There were also issues related to the genetic coding of facial movements.

The role of movement of the facial surface was first examined by John N. Bassili an associate professor of psychology at the University of Toronto. He recorded the various different facial expressions that appeared by making use of black makeup materials to cover the faces and white spots scattered on all over the faces. This technique of using white spots on the faces was proven to be sufficient enough to recognise the different facial expressions that were performed. [14]

Since the 1970s there have been numerous developments of systems that describe the various different movements of facial expressions, however the most well-known facial movement system originally developed by Paul Ekman and Wallace Friesen in 1976 was Facial Action Coding System (FACS). [10] The goal of this system was to be able to notice all facial movements that are visually visible. This system divides the various facial expressions into 46 small facial movement units which are respectively called ‘action units’, these 46 action units correspond to facial muscle activations, which when put together produce facial expressions. [10] [30]

1.2 Psychology of the face

“A face that had a story to tell, some of them speak not. They are books in which not a line is written, save perhaps a date”[Henry Wadsworth Longfellow, Patrick J. Byrne, Importance of facial expression, Google - Online]

Facial expressions play a vital role in life; it is believed that people tend to look at the face more than any other object. [1] The face and its expressions are extremely important factors for others recognition as well as being a major identification factor of age, ethnicity and gender. The face and its expressions hold the basic social information. [19]

Facial expressions are considered and believed to be our primary means of communication. It is a major form of nonverbal communication as many psychologists and people perceive facial expressions and body language to be a more honest indicator of true feelings or opinions, which is the reason many prefer face to face communication rather than verbal or any other form of communication. [20] [28]

1.2.1 Emotions and Facial Expressions

According to Charles Darwin’s argument in 1872, expressing emotions is an essential necessity for human life and survival.

Darwin (1872) was the first to come up with the idea that facial expressions are universal. However in order to test his theory he sent out questionnaires related to expressions. These questionnaires consisted of questions which requested people to judge different expression from various different races and religions. [1] [11]

Later, Darwin combined all the results with his personal observations and came to a conclusion that expressions are the same everywhere. After coming to such a conclusion Darwin’s attempt was to discover the reason behind how it could be possible that all humans expressed their emotions in the same way. After his research and attempts, Darwin finally concluded with the statement that facial expressions are not learnt but are inherited. [1] [11] [19] [20]

Expressions are very closely linked to emotion and the majority of the time is involuntary. It has been proven that certain expressions due to specific emotions are next to impossible to avoid. One such example is someone who may be trying to avoid insult to someone they find unattractive might actually show a slight expression of disgust before returning to a neutral expression. This also shows that one expression from a certain emotion may lead to another associated expression. [27]

Paul Ekman (1960’s) is a well known psychologist for his research and studies on emotions and expressions, who also carried out a series of experiments to test Darwin’s statements. In 1996 Ekman presented six photographs of different expressions from people in USA, Japan, Argentina and Chile. His results and reports proved that people from all the countries attributed the same expressions to the same emotions.

[1] However Ekman was determined and therefore along with Friesen (1971) Ekman conducted further studies with a broader range of people from around 21 countries. [19] [20] The fact still remained that these results and findings all showed similar responses, keeping in mind that these studies were demonstrated in a broad range of places, proves that there may be differences in how emotions are shown and dealt with. However, the actual emotions are common in all human beings. In 1982 Ekman and Friesen joined hands with Ellsworth, the three then went on to review the various studies carried out. [9] [11] [17] They finally came to a conclusion that there are six basic expressions: Happiness, Anger, Sadness, Fear, Surprised and disgust.

1.2.2 The Portrayal of Emotion

As mentioned through Ekman, Friesen and Ellsworth came to a conclusion that there are six basic emotions which have been briefly discussed in this section.

Happiness - Expressions of happiness are one of the easiest to identify whether it be personal observation of a person or even photographs. These specific expressions are directly linked to positive attitudes and thoughts. However happy expressions can also be used to deceive in terms of hiding stress or sadness. ‘Almost all of the empirical research has shown that happiness is most easily recognised and distinguished from other emotions [9]

Sadness - These expressions are traditionally linked to crying which is also how this emotion & expressions are portrayed through personal observation as well as in photographs. [9]

Anger - Angry expressions are usually the signs of a person being annoyed by someone or something which commonly leads to conflicts, violence and can lead to serious issues. As explained by Ekman in his book ‘Emotion in the human face’, Angel may be activated by distress or pain as well as both put together. [9]

Surprise - surprising expressions are usually very brief and short term expressions, these occur due to something unexpected or could also be linked to a happy/sad emotion too. [9]

Fear - fearful expressions tend to portray feelings of threat or nervousness. These expressions could be misunderstood with anxiety expressions as fear and anxiety share a very close link. Surprise and fear however are classified as more similar to each other in facial components. [9]

Disgust - expressions of disgust could occur due to any reason such as a smell, a touch, an unattractive site or something we may dislike such as creatures or different food. [9]

Psychology is a vital factor for facial expressions and human emotions as it is the only means we have by which we can understand the emotions and the expressions both through various psychological theories, statements and studies. Psychological theories from Psychologists such as Paul Ekman, Charles Darwin and Friesen [9] [10] [11] are the main areas of interest as their studies and theories are directly related to facial expressions, emotions and the reasons behind them.

1.3 Current 3D modelling and animation packages

This section contains a brief summary of four 3d packages currently available in the market, which have similar three-dimensional modelling and animation uses. This section also includes a brief comparison of the features of each of these four packages and detailed information about 3D Studio Max and MAXScripts, which is the core development environment for this project.

The four packages covered in this subsection include; Maya, Light-wave, Softimage XSI and 3DStudio Max. These four packages enable 3d application users to construct models using simple objects, such as Boxes, Planes, sphere etc and are all commercial packages.

The most popular method of modelling and one which is used in all four of these applications is polygon modelling. This method is used to represent surfaces of the object using polygons. [26] Surfaces are two-dimensional manifolds and polygons are objects that are bound by their own edges and sides. When these edges and sides meet they are called points, which can be referred to as polygon vertices or corners. [24]

1.3.1 Summary of the four 3d packages

Package: Maya

Developed By: Alias Wave-front

Maya is a very high-level 3d modelling and animation package which was original developed by Alias Wave-front but is now owned by Autodesk. Maya is mainly being used within the entertainment industry such as movies and TV programs; it is also used in the development of computer and video games. Although Maya is not the most popular package currently in the market it is one of the most widely used among high-level graphic developers, which places it in second position on the table of animation packages after 3D Studio Max. The great aspect of Maya is that it has its own scripting language called Maya Embedded Language (MEL) which can be used to develop various different features into Maya. It also allows its users to create their own customizable interfaces similar to 3d Studio Max scripting language (MAXScript). [1] [31]

Package: Light-wave

Developed By: New-Tek

Light-Wave also know as ‘Light-Wave 3D’, was one the first packages to be developed for 3d modelling, animating and rendering of objects. Research shows that it one the most difficult packages to use and become familiar with, the package was very slow with rendering as it used up a lot of hardware which degrades its performance. It consists of a C type language to customize objects and interfaces. This is very powerful package but needs enormous amounts of hardware power to prove its abilities. [1] [31]

Package: Soft-Image-XSI

Developed By: Avid Computer Graphics

Softimage currently known as Softimage-XSI is a very strong package for modelling objects using the polygon modelling method. It is the latest package to be released among the four packages explained in this subsection. This package has a very user friendly environment which makes it more inviting to users who are just beginning to model and animate three-dimensional objects. It also has the ability to develop customizable interfaces using scripting methods similar to MAXScript and Maya Embedded Language (MEL). [1] [31]

Package: 3D Studio Max

Developed By: Autodesk Media and Entertainment

3D Studio Max is the most widely used and most powerful three-dimensional modelling and animation package currently available in the market. The high level professional tools and animation effects it comprises are the result of this package being at the top of all three-dimensional animation packages, currently ranking at number one posistion. It consists of a flexible plug-in architecture with a huge amount of open source and commercial plug-ins available, for example light effects, fluid dynamics, ray tracing and many more.

This package is mainly used by computer and video game developers, TV commercial studios, architectural visualisation studios and movie effects. These abilities of 3D Studio Max make it the leading and most powerful package today; hence the reason for it being the most expensive software currently on the market. [31] 3D Studio Max has its own scripting language similar to Maya’s embedded language (MEL) [1], called MAXScript. MAXScript provides the ability to practically develop features and customized tools within 3D Studio Max by just using its own scripting language. There are many sources of help and support provided for MAXScript on the internet and there are quite a few text books available to aid one in using MAXScript. [6]

3D Studio Max has a very easy to use interface and is not very difficult to get familiar with for beginners, although high-level modelling and animation techniques can be difficult to adapt to for beginners, it provides many tutorials within the package and online to get started on modelling and animating. [31]

1.3.2 3ds Max

The first 3D Studio package was developed by the Yost Group to work within the DOS platform and was published by Autodesk. The package was then purchased by Autodesk and they entirely reviewed and changed the development of the product in the next two versions that were released.

After the fourth version of 3D Studio the product was upgraded from the DOS to the Windows NT platform and the name of the product was changed to 3D Studio MAX. This package was then released by Autodesk’s division of media and entertainment called Kinetix. The product again changed its name to ‘3ds max’ and was also branded with the Autodesk logo by the release of version 8. The product is currently still known as the name of ‘3ds Max’ but has recently released a new package called ‘3ds Max 2008’. [23] [31]

3ds Max consists of many different commands which can be used to model any type of three-dimensional graphical object. It has been designed and developed in an object-oriented programming language called C++. 3ds Max is being used by many companies such as Rockstar Games, Relic Entertainment, Ubisoft and many more. [23] The product has also been used in many Hollywood movies to create animations and effects such as Jurassic Park, The Matrix Reloaded and Spider-Man 3. There have also been numerous games developed with the use of 3ds max such as Call of Duty, Far Cry, and Splinter Cell. [23] This shows that 3ds Max is widely used around the world and is a very powerful package for animations.

1.3.3 MAXScript

MAXScript is a programming language built-in 3ds Max, it is an object-oriented language similar to C++ but is much easier. MAXScript can be used to perform everything that 3ds Max can do such as geometry, cameras and lights. Therefore it is confined specifically to 3ds Max, however the limitation of MAXScript is that it cannot be used to create plug-ins as they are written in C++, there is a separate kit called Max SDK (Software Development Kit) which can be used to create plug-ins for 3ds Max. This project is based on creating a tool by using the scripting methods within 3ds Max. [6]

MAXScript is easier and a faster language, it is also limited and processes slower than C++. MAXScript enables users to control the programs interactively by the use of the command-line listener window; develop utility panels or modeless windows to create a custom standard user interface with rollouts, buttons, labels and much more. It can be used to extend the current 3ds max user interface; build customized import and export tools using the American Standard Code for Information Interchange (ASCII) and binary input/output file and build batch processing tools for example a script to compute batch rendering [6].

MAXScript was initially introduced as a plug-in within release two of 3d Studio MAX. Later it became part of the core code of 3ds Max. The functionality and usage of MAXScript has been significantly improved over the new releases, one of the main improvements include the insertion of macroScript (.mcr), this new scripting method allows users to call scripts as embedded code from within the 3ds Max user-interface and as keyboard shortcuts, menus or quad menus. The other improvement included a system called Function Publishing System (FPS); this new system enabled plug-in code developed to be made available to MAXScript. [6]

3ds Max initially included only one type of script which was called MAXScript with the extension .ms, as max script started to expand there was also an increase in the number of script types. There is now the macroScript (.mcr), the encrypted max script (.mse) and also there are embedded scripts that have no extensions, such as expression controllers. [6]

The macroScript are scripts that can be generated automatically by a series of user operations or even by physically typing the macroScript. The encrypted max script type is used to protect coding or software. A ‘.ms’ and ‘.mcr’ script can be converted into an encrypted (.mse) script which encrypts the script making it unreadable but at the same time it still can be executed and used. [6]

“Macro Scripts are scripts that are associated with toolbar buttons and are executed when the corresponding toolbar button is clicked. Macro Scripts have to be defined with the macro Script definition construct and can then be associated with a toolbar button by right-clicking a Shortcut toolbar or Tab and choosing Customize. The Customize User-Interface dialog is displayed, which lets you choose from either Command shortcuts or Macro Scripts. Macro Scripts are essentially pieces of MAXScript code that have a name, category and optionally a tooltip and icon. Macro Scripts do not automatically create user-interface items. If you want a Macro Script to display a dialog, you will need to create a rollout floater window and rollout(s)” [21]

“After MAXScript evaluates a macro Script construct, the Macro Script definition will show up in the appropriate category list in the Customize User-Interface dialog.” [21]

“macroScript <name> [ category:<string> ] [buttonText:<string>] [toolTip:<string>] [icon:#(<string>, <index>) | icon:<string>] [silentErrors:<boolean>] ( <macro_script_body> )” [21]

MacroScript serves as the core for this project, and serves as a simple way to develop the GUI and functionality for the proposed tool. Figure 1A shows simple script entered into the MAXScript listener window which creates a sphere and sets its radius. This is a good starting point for learning and understanding MAXScript.

Another good learning point is using the macro recorder, which captures the actions that the users carry out within 3ds Max and generates MAXScript commands for those actions. Figure 1B shows the same sphere created using the macro recorder. Once the user has created the sphere they can select the code that appears in the macro pane and drag it to the main toolbar. Once the icon is in the toolbar the user can click on it which will then run the script and create another sphere. [6]

s = sphere()

$Sphere:Sphere01 @ [0.000000,0.000000,0.000000]

s.radius = 50

50

Figure 1A: Script creates sphere.

macroScript Macro1

category:"DragAndDrop"

toolTip:""

(

Sphere radius:50 smooth:on segs:32 chop:0 slice:off sliceFrom:0 sliceTo:0 mapcoords:on recenter:off pos:[7.26169,67.0988,0] isSelected:on

)

Figure 1B: Script creates sphere using macro recorder/macro script.

Macro scripts are the same as MAXScript they have the same code but with additional information such as name, category, button text, tooltip and icon. Button text, tooltip and icon are optional. [21]

Figure 1C shows example source code of creating a floating window with a rollout within the window using macroScript. [21]

macroScript FloaterWindowExample

category:"FloaterWindowExample"

tooltip:"FloatingWindow"

(

rollout Example "Example"

(

)

theNewFloater = newRolloutFloater "Example Floating Window" 300 220

addRollout Example theNewFloater

)

Figure 1C: Source code creates floating window

If the same code was developed using the original MAXScript (.ms) extension instead of the macroScript (.mcr), then the window will appear right after the user evaluates the script, where as the macroScript is more efficient and organised as one can use a button in the toolbar or a keyboard shortcut to load the interface. When the user clicks on the button or uses the keyboard shortcut the script is executed and the window automatically appears on the screen.

“NewRolloutFloater <title_string> <width_integer> <height_integer> [<top_integer> <left_integer>]

Creates and opens a new rollout floater window with the title and width and height given. If you don't supply top and left coordinates, the window will open centred in the screen. The width of the 3ds Max command panel is 218, in case you want to duplicate its width for precisely accommodating Utilities panel rollouts. This method returns a Rollout Floater value to which you add rollouts.” [21]

“addRollout <rollout> [ <rolloutFloater> ] [ rolledUp:<boolean> ]

If the optional second argument is specified, it must be a RolloutFloater value as returned from the NewRolloutFloater() function. The rollout specified by the first argument is appended after any rollouts previously in the window.” [21]

The floating window can also be created by using variables within the script, which would be a different approach to the one shown in figure 1C. “Variables have an attribute called scope, which determines where in MAXScript code a variable can be accessed. MAXScript has two kinds of variable scope, global and local. Global variables are visible in all running MAXScript code and hold their values until you exit 3ds Max. Local variables are directly visible to code only in the lexical scope currently in effect, and hold their values only as long as the current scope is active. Once a scope is no longer active, you can no longer access the contents of a variable local to that scope. This is similar to how most modern programming languages implement variables.” [21]

For the purpose of this project there will only be the use of ‘Global’ variables. The difference between the two scripts is that a .ms script does not have the script name, category and tooltip information within the scripts coding and does not allow the use of buttons to launch the scripted tools. Therefore this project will make use of macroScript for the development of the morphing tool.

1.4 Current Morphing Software

There are currently 5 top morphing applications in the market, which have been specifically designed to ease the process of morphing face/character models. The morphing applicatications discussed in this section are FantaMorph, MorphBuster, Morpheus, FaceMorpher and FunMorph.

All these application are in the top ten of best morphing tools and include the same morphing methods. A brief review of the five applications and some of most popular plug-ins for 3ds max have been given in this section, which will be used to design and implement the new morphing tool in 3ds Max. [32]

Applications: FantaMorph, MorphBuster, Morphues, FaceMorpher and FunMorph.

Developers: Abrosoft, SoftBusters, Morpheus Software LLC, Luxand Developers, ZeallSoft Inc.

All five applications allow users to select the original image that is to be morphed and the image that will be morphed into the original image. The users can morph the image by just setting the different key points on the face and then by clicking on one button the morph can be created and preview at the same time. It also consists of an image library to keep the morphs created. The applications allow users to import images of many formats such as JPEG, BMP and GIF. They also allow users to add text to the images, set the number of frames per second and much more. Users are able to create numerous morphs on one image using any of the five applications. [32]

At present there are applications such as Absolute Character Tools which is a plug-in for 3Ds Max, which enables muscles in the face to be linked to the character and enable it to move independently within the skin. There are also other tools which include the ability to edit width, length and position of the muscles. [1] There are even more sophisticated applications such as Morph-O-Matic [33] which is another plug-in for 3ds Max and is a very popular software for industry animators. It enables users to easily apply lip movements, facial expressions and synchronise them. [29]

1.5 Modelling and Animating Methods

Facial modelling and animation has always attracted researchers in several areas, including computer vision, computer graphics and cognitive science. A graphics-based human model provides an effective solution for displaying information. The techniques for modelling and animation have been discussed in this section.

1.5.1 Modelling Methods

The most common method of constructing a three-dimensional face or head model is by using a two-dimensional sketch or photograph from two different angles; for example the front and the side of the face object. [8] These sketches or photographs can be used as templates to construct the three-dimensional face model; this method is called inflation or extrusion modelling.

The designer can model a three-dimensional face by tracing around the outline of the object in the sketch or photograph. [7] There are a range of modelling techniques that can be deployed to construct three-dimensional models, such as polygons and splines/NURBS. [8] There a few other techniques that can be used to model objects but this project only deals with the polygonal and splines/NURBS techniques. The following subsection discusses these techniques in more detail.

1.5.2 Polygon Modelling

`“A polygon is a portion of a plane bounded by three or more lines of segments”

[Analogy by P. Ratner, 2004][8]

Figure 1D: Polygon Sphere Model.

The designer can make use of the polygon modelling technique to display geometric details of an object. A polygon is graphically represented using a vector described as the polygon’s normal. A polygon mesh also known as an unstructured list is a collection of polygon objects and vertices linked together in to a curve. A vertex is the basic object used in mesh modelling, which are points in three-dimensional modelling; an edge is formed by connecting two vertices in a straight line. [8] Figure 1D shows a polygon model of a sphere.

A common method for building meshes is called ‘box modelling’; this method is used to overcome the disadvantage of hard edges in polygonal models. Box modelling makes use of two distinctive tools, the first one being the subdivide tool, which is self explanatory from its title. This tool basically adds extra vertices and splits the objects edges and faces into smaller particles.

For instance taking an example of a square the subdivide tool can be used to divided the square into four smaller squares by adding one vertex in the middle of the square and one vertex on each edge of the square. [22] [26] The second tool is called the extrude tool, this tool can be used to create an identical new face of the object at task. The new face would be of the same size and shape. This new face would then be connected to the edges of the original object by a face, again taking the example of a square when this extrude tool is applied on the square face it would create a cube. This box modelling technique is used by many developers as it aids in creating a smooth object such as a head model. [7] [8] [22] [26]

1.5.3 Splines/NURBS (No uniform rational B-spline)

NURBS represents curves and surfaces and is a mathematical model used in computer graphics. The edges of an object are defined by the use of Splines and NURBS. Wireframe mesh can be constructed by connecting a number of splines or NURBS; this then makes it possible for the designer to build their desired shape.

Smooth curved surfaces can be created using NURBS which are flexible lines. Splines consist of flexible line segments which are defined by edit points that are called vertices. [8] Figure 1E shows a NURBS model of the same sphere.

Figure 1E: NURBS Sphere Model

Careful examination of figures 1D and 1E revealed that a polygon model has a more segmented appearance where as a NURBS model is very smooth. However, the polygon technique is most widely used when it comes to modelling faces or head models as it is a quicker option, especially for beginners. To form a smooth polygon models one can make use of the mesh smooth modifier [22] within 3ds MAX once the model has been completed.

1.5.4 Slider and Spinner Controls

Sliders and spinner controls are basically a simple way which helps to control the morphs after they have been created and set. As it is believed that if the facial expressions are complicated the set up will be much more sophisticated. [16] One such example may be if you had 17 expressions, you would need 17 sliders and spinners to control the 17 morphs.

Each morph will be associated with a slider and a corresponding spinner. [1] Sliders and spinners have value ranging from 0 to 100, where 0 would be the neutral position and 100 for example, would be the happiness expression.

1.5.5 Facial Rigging and Morphing

Facial rigging is the most commonly used and easiest attempt to stimulate the muscles in the face. Someone who is animating would create bones connected by joints which are located under the characters skin, exactly the same way in which human anatomy is. [1] [4]

In the process of rigging the face, the animator locates the bones in areas where movement is going to be created however if a rather sophisticated set up is required the animator may create a set up which is much more sophisticated than the standard anatomy set up. One such example could be bones may be located under the eyebrow to pull a rather exaggerated look. [16] [18]

Therefore the bones are linked with either a smooth or rigid binding technique to the characters mesh, after which the rig is set up and once the rig is set up in the correct manner, animation can be started by a simple action of moving the joints which are connected to the bones in the modelled face. [1] [18]

“Morphing is an animation technique similar to tweening in 2D animation. A Morph object combines two or more objects by interpolating the vertices of the first object to match the vertex positions of another object. When this interpolation occurs over time, a morphing animation results. The original object is known as the seed or base object. The object into which the seed object morphs is known as the target object. You can morph one seed into multiple targets; the seed object's form changes successively to match the forms of the target objects as the animation plays.” [22]

Facial animation morphing can be created once the character/face has been modelled. The modelled character will act as the base object from which the different expressions can be sculpted. Each expression has to be sculpted on the base object and then a copy of the base object with the expression sculpted needs to be created. This has to be done for each expression that is created.

Once all the expressions have been created, they need to be added to the morpher modifier stack. This can be done by selected each face model one by one. After all the face models have been added, they can be selected from the morpher modifier stack list and a morph key can be created for each of the expressions set on each of the face models. [8] [22] The animation can then be played and the base object will be morphed into the expressions that have been added to the timeline as a morph key.

All of the essays in the free essays section were written by students and then submitted to us to display and help others. Thanks to all the students who have submitted their essays to us. You should not hand in our essays as your own. We do not condone plagiarism! If you need custom essay help, then have a look at our essay writing services.

Sign up and be the first to receive our latest offers: