Wiley Introducing 3ds Max 2008
Contents
1. PRODUCTION WORKFLOW 5 Writing a Script Whether a CG project has a ton of dialogue or doesn t have a single spoken word both the project and you will benefit from having at least a rudimentary script Even abstract ani mations can benefit from a script that presents a highly detailed explanation of timings and colors whether that script is typed neatly or scribbled on a cocktail napkin A script serves as your intention Without having a clear intention of what you wish to say with your film your production time may as well be spent lying on a lounge chair drinking iced tea you will not get much done in either case Storyboards A storyboard is the next step in defining the action laid out in the script It shows the tim ing and framing for the camera as well as the action and dialogue if any To create an effective storyboard you should dissect your script into scenes and further dissect the scenes into shots with each shot presenting a distinct view from the camera or a distinct cut of action Each storyboard panel describes what is happening in that shot The panels show you the overall action of the project in a linear shot by shot fashion and how it should come together in editing Even if your storyboards are simple ones composed of stick figures they are important to preproduction Concept Art Conceptuals also called concept art are the design elements that are needed for a CG production If you don t have concept a2. 8 Introduction to Animation and Chapter 9 Character Studio and IK Animation cover animation techniques in 3ds Max Lighting Lighting is the most important aspect of CG production This area is where you get to see your models and textures as well as set the mood of the project During lighting you set up virtual lights in 3D space that will illuminate the objects in your scene when it comes time to render Lighting can drastically change how your scene looks Using lighting wisely is a learned skill and it takes tons of time to master there are no shortcuts to becoming a good lighter Not only are you dealing with the aesthetics of getting your shot to look great but you are also dealing with rendering issues and bottlenecks that could make rendering your shot a nightmare These issues come up with much larger scenes than the ones you will be using in the first years of your CG education however it s important to start learn ing how to use lighting efficiently as well as aesthetically Lighting can make or break all your hard work You can use lighting to affect the believ ability of your models and textures as well as to create the proper mood and tone 12 CHAPTER 1 BASIC CONCEPTS In this stage of the pipeline the lighting workflow begins when you are texturing your objects You need to light your scene initially to evaluate how your textures are progressing However the final lighting and look really happen after eve
3. In the first frame of this sequence a keyframe is set on the position rota tion and scale of the cone On frame 30 the same properties are again keyframed The computer calculates all the movement inbetween 26 CHAPTER 1 BASIC CONCEPTS Weight Weight is an implied facet of design and animation Weight denotes the heaviness or pres ence of an element in a design The more weight an element has the more power it has in the composition The weight of an object in a composition is affected by its color its con trast its background its position in the frame and other variables The weight of an object in animation roughly follows that idea but more pragmatically denotes the actual weight of the object as it relates to its environment Giving an object a good weight in animation is critical to the believability of the animation You will have a chance to animate an object and edit the animation to give it weight in Chapter 8 s Bounc ing Ball and Knife exercises Weight in animation is a perception of mass An object s movement and how it reacts in motion and to other objects are critical to conveying the feeling of weight Otherwise the animation will look bogus or cartoonish Over the years animators have created a set of techniques to give their subject weight in animation Manipulating these concepts correctly in your work will greatly help your animations Squash and Stretch Squash and stretch is
4. You can render one scene while another scene is in production but working on a sys tem that is rendering is not advisable unless you re using a dual processor machine with plenty of memory Once everything has been rendered properly the final images will be sorted and the CG project assembly will begin Rendering is the subject of Chapter 11 3ds Max Rendering PRODUCTION WORKFLOW Compositing editing and adding sound are advanced postproduction activities and a detailed discussion of them is beyond the scope of this book However a multitude of books are available on these topics for further study Compositing CG is often rendered in different layers These segments ultimately need to be put back together For example in a scene where multiple characters interact each character can be rendered separately from the others and from the setting Compositing is the process of bringing together rendered elements to form the final scene usually using compositing software such as Autodesk s Combustion Adobe s After Effects or Apple s Shake Compositing can greatly affect the look of a CG project and professionals consider it to be an integral part of CG creation Compositing programs allow you to compose CG ele ments together but they also give you additional control over color timing and a host of other additions and alterations you can make to a scene A lot of students assume that they need to render a scene in a single pas
5. a cartoon concept that allows a character to physically squash down when he is landing from a jump or stretch out thin while he is jumping up The overall mass of an object should never really change When you squash an object down you should also reduce its height to make it seem as if it s squashing down Similarly when you stretch an object up you should also thin it This technique will make a charac ter seem to respond to gravity You will see how this applies in the Bouncing Ball exercise in Chapter 8 Ease In and Ease Out Things in the real world don t immediately come to an abrupt stop There is always a slowing before a stoppage no matter how fast the stop may be This is called ease out Just as objects don t suddenly stop they don t immediately start moving either Pretty much everything needs to accelerate no matter how fast it begins moving This is called ease in The mechanics of ease in and ease out will also be illustrated in the Bouncing Ball exercise in Chapter 8 Follow Through and Anticipation Exaggerating the weight of an object in animation is sometimes necessary Objects ending an action usually have some type of follow through motion For example a ponytail on a girl jumping down from a chair will continue to move after she lands on the floor There BASIC 3DS MAX TERMS AND CONCEPTS 27 should be a slight resting follow through to her action For example she may bend slightly at the waist to center he
6. adjustment on an object that is based on a fixed reference such as World Space An absolute scale of 2 will scale the object to a flat unit of 2 Relative refers to an adjustment made to an object that takes its current state into account Scaling with a relative value of 2 will make that object twice its current size Track In 3ds Max a track is a display of animation data for an animated object When an object has animation on several parameters such as Translation X and Y as well as Scale in X and Z it is said to have four tracks One track defines one animation on one parame ter of that object on one axis SUGGESTED READING The more you know about all the arts that are used in CG the more confident you ll feel among your peers To get started check out the following excellent resources Art and Design These books provide valuable insights into the mechanics and art of design The more you understand design theory the stronger your art will be Bowers John Introduction to Two Dimensional Design Understanding Form and Function New York John Wiley amp Sons 1999 Itten Johannes Design and Form The Basic Course at the Bauhaus and Later New York John Wiley amp Sons 1975 Ocvirk Otto G and others Art Fundamentals Theory and Practice New York McGraw Hill 1997 Wong Wucius Principles of Form and Design New York John Wiley amp Sons 1993 BASIC 3DS MAX TERMS AND CONCEPTS 29 CG CG has an interesting h
7. and moving into CG workflow we discussed how productions are gen erally run Next you learned the different types of tasks used in CG production and the professional specialties that have arisen from them After that you learned about core computer concepts color space and output formats Finally you saw a preview of some of the key 3ds Max terms and concepts that are covered in depth in the following chapters No matter how you use this chapter or even if you skip it entirely to get right to the action there is a lot of background information here that can be useful in your overall knowledge of CG production Although it takes some extra time to develop a good foun dation having one is an excellent idea because gaining true understanding of a subject is fundamental to its mastery Having said this take the rest of the book as it comes enjoy the challenges of the exercises and remember that some frustration with an exercise will inevitably help you learn the concepts better so keep at it
8. are aligned However when the object is rotated its Local Coordinate System rotates with it Because of this an object created in a Front viewport for instance will have a different Local axis than if it were created in the Top viewport COORDINATE SYSTEMS 23 24 CHAPTER 1 BASIC CONCEPTS Figure 1 5 The Object space of the box aligns with the World Space Figure 1 5 shows a box The X Y and Z axes of the box are displayed in the center of the box and align with the axes of the home grid which shows the World Space axes displayed in the lower left corner of the window When the box in the scene is rotated Max retains them as Local space instead of substi tuting its own axes The X axis of the box does not change Now the Local axis and the World Space axis are not aligned This is a very good feature because it allows you to manip ulate the box based on its original Local axes Basic Animation Concepts A wealth of information regarding animation concepts and techniques is available on the Internet There are tons of books out there that also teach the basics of animation In this very brief section you will be exposed to a few important concepts behind animation These concepts will help you better understand what yow re doing in 3ds Max Frames Keyframes and In Betweens Animation is based on change over time so you need a unit of measure for time In ani mation time is almost always expressed in frames One
9. or other unit of measure in the horizontal and vertical directions Because raster images are based on a fixed grid these images do not scale larger very well The closer you zoom into a raster image or the larger a raster image is scaled the larger the pixels seem which makes the zoomed or enlarged image blocky or pixelated To use larger raster images you need to start with a higher resolution when the image is created The higher the resolution the larger the file size will be Figure 1 3 shows what happens when you blow up a raster image CORE CONCEPTS 15 Figure 1 3 A raster image does not scale up very well Here is the front of a stereo receiver that has been blown up by several hundred per cent The pixels look blocky 16 CHAPTER 1 BASIC CONCEPTS So why are raster images even used if you can t scale them well Most common displays and output methods such as television or computer screens or even printers are actually raster displays The display devices need raster images to display the pictures properly The term raster originally referred to the display area of a television or computer monitor To form an image the electronics in these devices paint it as a grid of red green and blue pixels on a glowing screen Every image generated by a computer therefore must either begin as a raster image or be rasterized as part of rendering for display Vector Images Why does the interface for 3ds Max l
10. the animator s Character TDs can also work with motion capture systems to transfer motion to a character They use recorded data from a live action stage where actors are outfitted in special equipment that records their movements Effects TDs are specialists who generally animate special effects such as tornadoes clouds or explosions These specialists generally rely on particles and dynamics as well as textures lights and rendering tricks to perform their effects This specialty requires a strong eye in all stages of CG production and a strong ability to troubleshoot and come up with solutions that are frequently not standard techniques in a program such as 3ds Max Lighters light and render a scene once it is completed Lighters specialize in being able to final a shot in other words to complete a shot for final approval and output A good lighter needs to understand how models and textures behave in a scene and sometimes must remodel or retexture an object to make it work Good lighters also need to be good 14 CHAPTER 1 BASIC CONCEPTS compositors because so much of CG can be broken into elements that later need to be put back together For example the shadows in a scene may be rendered separately from the rest of the scene Compositing as a specialty requires much less knowledge of CG although today s com petitive compositors should know as much as they can cram in their brains about CG Compositors not only have to assemble a
11. 30fps animation at 24fps will create a faster moving animation that will either skip some frames or end later than it should Games do not typically have a set playback rate for animation When a scene is created for a game the assets in the scene are rendered and played back on the user s computer system in real time therefore many factors contribute to the playback speed of scenes created for games On the Internet typical playback speeds for animated content on websites average about 12 to 15 frames per second about half of what you would see on a TV or film screen This saves the viewer considerable download time because the files are much smaller Coordinate Systems Coordinates are numerical representations of where an object is in 3D space Every object in 3ds Max has a coordinate of where it exists Without this coordinate it would be gone poof into thin air Max s 3D space is organized with the Cartesian coordinate system which uses a three pronged axis to define width height and depth as X Y and Z respec tively The overall coordinate system in Max is called the world coordinate system It is an absolute coordinate system that is fixed and unchangeable Objects in Max can have their own coordinate systems as well When an object is created it has its own width height and depth again expressed as X Y and Z Upon creation the local coordinate system belonging to the created object and the world coordinate system
12. CHAPTER 1 Basie Concepts Any way you cut it everyone learns in different ways especially when they are learning about Autodesk 3ds Max 10 or any other computer graphics CG package You should realize that the best education you ll get is through months or even years of work ing with the software in different capacities Ask any successful student and they will tell you one thing There is no such thing as book smarts when it comes to good CG pro duction it all comes down to what you can achieve Achievement comes only from practice You can t avoid the many pitfalls of produc tion work without falling into and climbing out of them Some readers may find this idea frustrating but it is an intractable truth The more you work with 3ds Max the better you will become with it And the more you struggle fail and recover the more you will learn This chapter introduces you to basic concepts in computer graphics production Topics in this chapter include How to Read This Book What Is CGI Production Workflow Core Concepts for Animation 2 CHAPTER 1 BASIC CONCEPTS How to Read This Book First and foremost you don t need to read this book cover to cover and front to back to get the most from it If you are the type who loves to jump right into the pool to learn to swim then skip this chapter and jump into Chapter 2 Your First 3ds Max Animation to start working with the interface If you already know how to nav
13. D Space 3D space the virtual canvas in which you create 3D objects is a simulation of space that is divided into three axes X Y and Z representing in loose terms left right up down and in out Figure 1 1 shows 3D space in a Max window So what the heck do you with 3D space In many ways setting up a scene in CG is like setting up a photo shoot With a photo shoot you gather your subjects and pose them in your composition You set up lights to illuminate them as dramatically or naturally as you need them to look and then take pictures with your camera framing the composition as you like it Next you develop and fine tune your photos or adjust them with tools such as Photoshop before you print them Finally comes the happy part of showing them off and sharing your work with others Computer graphics production has much the same workflow although with CG you create nearly everything from scratch in your 3D space Instead of running out and hunt ing down the perfect models and all the props and settings you need for a photo you cre ate them You model everything first and then apply colors and texture to the surfaces you created Once you lay out your scene with all the settings and props you need you set up your CG lights to illuminate the models Lighting is perhaps the most important aspect of CG as this stage of CG production really makes or breaks a scene Once your lighting is ready you render the scene This is akin to developing
14. The emerging television standard sometimes also referred to as 1080i 1K Academy 1K refers to 1024 x 768 Typically the lowest allowable resolution for film 1000 pixels across production at Academy ratio Because film is an optical format whereas TV is a raster format there is no real set defined resolution for film Suf fice it to say the higher the better 2K Academy 2K refers to 2048 x 1556 Most studios output CG for film at this resolution 2000 pixels across which gives the best size to performance ratio 4K Academy 4K is 4000 pixels 4094 x 3072 A high resolution for film used for highly detailed across shots Any discussion of resolution must include the matter of aspect ratio Aspect ratio is the ratio of the screen s width to its height There are a variety of standard aspect ratios Table 1 2 Table 1 2 STANDARD SIZE NOTES Standard Aspect Academy Standard 1 33 1 or 4 3 The most common aspect ratio The width is 1 33 Ratios times the length of the height This is the NTSC National Television Standards Committee televi sion aspect ratio as well as the aspect ratio of 16mm films and some 35mm films especially classics such as Gone with the Wind Widescreen TV 1 78 1 or 16 9 With HD and widescreen TVs gaining popularity the 16 9 standard is commonplace now This aspect is used in HD programming and is also the aspect ratio of many widescreen computer moni tors and laptops This aspect is very close to how most film
15. a Flash cartoon plays on a web page you are visiting for example the informa tion for that cartoon is downloaded into your computer in vector form The data contains the position size and shape of all the elements of the animation The vector information is then converted into raster images called rasterization so you can view the final image or animation Your computer renders this information on the fly in real time into a raster display that you can enjoy on your screen This is roughly how things are done with 3D programs such as 3ds Max You begin your work in Max s 3D space in vectors When you are ready to render Max renders the scene contents into raster images or movie files that you can display You use the tools in 3ds Max to change the geometric information which in turn changes the scene and then rerender to show the output Changing a raster image such as a digital photo alters that CORE CONCEPTS 17 original file assuming you do not have a backup file once you save your work because it directly affects the pixels of the image Figure 1 4 A vector image of a girl at its original size left and blown up to a few hundred percent right shows no loss in quality The curves are not stepped or pixelated Image Output When you re done with all your CG you will probably want as many people to see your work as possible To accomplish this you will need to render the scene out to image files or a movie file These f
16. ail than needed than to give too little The detailing process will teach you a majority of what you need to learn about modeling This in turn will benefit your overall speed and technique With more experience you will be able to discern the level of detail you really need and work more efficiently Here is a quick rundown of some different kinds of modeling Character Modeling Character modeling includes the modeling of any characters in your scene from humanoids to animals to ordinary objects that are animated to life Most characters are organic forms such as animals humans aliens and so on However a talking cheese sandwich is just as much a character as the person holding it As a good character modeler you need to keep in mind the animation needs of a character when you re modeling It s important to know what you need from your shot way ahead of time so you can model appropriately Traditional characters such as humans need to appear seamless once they re modeled Character animation usually requires the model to deform in some way such as bending and warping at certain points like the elbows The pieces that make up the model may tear apart if the character is not built to accommodate deformation and movement Like the park bench we talked about earlier your character must be built with the level of detail required by the scene As a matter of fact you could wind up with multiple mod els for a single character that are b
17. dobe s Premiere or even Apple s Final Cut Pro If you don t have an editing program you can use the Video Post module in 3Ds Max This functionality is not covered in this introductory text however 7 8 CHAPTER 1 BASIC CONCEPTS Sound Sound design can add an entirely new dimension of reality or mood to any CG The audi ence needs to associate visuals with audio Even a basic soundtrack adds a boost to a simple animation by enhancing realism mood narrative and other aspects of its feel A good music soundtrack and well placed sound effects can be very powerful Sound effects such as footsteps can be added to match the action in the animation this type of sound effect is also known as Foley sound Just as with any film adding music to most animations can help with pacing as well as mood In this case music and live action sound design are pretty similar Once you combine everything you assess the sound needs The one glaring difference between CG and live action sound relates to dialogue When you shoot live action you generally capture the sound and dialogue live as you shoot With CG all dialogue needs to be recorded and edited at the beginning of the production phase In other words dialogue is a part of the CG preproduction and postproduction phases This is because animators need to hear dialogue spoken so they can animate images to match the lips of the characters speaking this is known as lip sync Recordin
18. frame is a single rendered image in an animation or a single drawing in a traditional animation Frame also refers to a single unit of time in your animation The exact length of that time depends on the final frame rate at which the animation will be played back For example at film rate 24fps a single frame will last 1 24 of a second At NTSC video rate 30fps that same frame will last 130 of a second Therefore a video based output will require more frames for the same amount of time as would a film Keyframes or keys are points at which the animator cre ates a pose for a character or whatever is being animated A keyframe in CG terms is a frame in which a pose a posi tion or some other parameter s value has been saved in time Animation is when the object travels or changes between keyframes Because the change happens between keys these frames are called in between frames The computer extrapo lates what needs to happen to get the object from its state in keyframe 1 to its state in keyframe 2 You will have plenty to keyframe in the coming chapters of this book In 3ds Max a keyframe can be set on almost any parame ter of an object such as its color position or size In reality you can set several keyframes on any one frame in CG ani mation Figure 1 6 illustrates a keyframe sequence Frame 10 Frame 15 BASIC ANIMATION CONCEPTS 25 Keyframe at Frame 1 Frame 5 Frame 20 Frame 25 Keyframe at 30 Figure 1 6
19. g the dia logue with actors also helps you animate the CG characters because you can imitate the gestures and actions of the live actors to help make your animation more real CG Workflow CG is a collaborative effort in which all the stages of production work hand in hand to achieve your final images Because of how CG comes together following a structured pro duction pipeline or workflow generally works best The layout of this book and its exer cises follow this overall workflow You begin by modeling texturing animating lighting and then rendering You can texture after you animate if you wish however for most projects the workflow described here is best What is universally true is that you will go back and forth between these stages several times throughout the process as you assess and further define your needs For example you may have to change some textures once you see the lighting or change a model according to an unexpected animation need Modeling Modeling is the topic of Chapters 4 through 6 of this book Modeling is usually the first step in CG creation and it can sometimes take the longest time You probably already know that modeling and modeling tutorials are popular on the Internet where you will also find a generous number of free and fee based models You might be able to find a lot of the props and characters you need for your scene there Unless you enjoy modeling take a look through Google or another search e
20. igate 3ds Max you can begin with any of the other chapters You can leave this chapter for bathroom reading when youre bored or the cable goes out If you like slowly dipping your toe in the water first then by all means sit back put on your bifocals and have a long soak in this chapter It will cover a lot of basic concepts and core topics with which you may or may not already be familiar It will gently ease you into the powerful program that is Autodesk 3ds Max 10 and into computer graphics in general No matter how you choose to read this book it is crucial that you approach the lessons as a way to begin the learning process This book aims to give you a solid foundation in many aspects of 3ds Max so that you can take this beginning and move on to more study In keeping with that ideal you will need to understand that you will not necessarily become proficient in any one aspect of 3ds Max just by reading this book Instead you ll gain an understanding of how it works and how you can work with the program to create anima tions and models Frequently students are annoyed by tutorials that don t seem to lead them to perfec tion in the first go around This is the case for all tutorials and indeed for all books that purport to teach anything The key is to use the lessons as a guideline not just once but repeatedly Doing a lesson multiple times will help you understand the concepts better and give you opportunities to try out a few differe
21. iles can be output and saved in many different ways The kind of file output you will use will be determined by a combination of disk space personal pref erence project needs and output requirements Color Depth An image file stores the color of each pixel as three values representing red green and blue Image type depends on how much storage is allotted to each pixel the color depth These are the color depths common to image files in CG production Grayscale The image is black and white with varying degrees typically 256 of gray in between Grayscale images are good for rendering out black and white subjects because no extraneous color information is stored in the image file 18 CHAPTER 1 BASIC CONCEPTS 16 Bit Color Display or High Color 5 Bit Image File Each color channel red green blue gets 5 bits of space to store its value resulting in an image that can display a maximum of 32 768 colors Each color channel has a limited range of shades but still gives a nice color image You might notice the gradation in the different shades of each color which can result in color banding in the image There is little use of these limited color images in CG work though you will find them used in web pages to maximize efficiency 8 Bit Image File This format is referred to as 24 bit color display or True Color especially in Microsoft Windows desktop settings Each color channel is given 8 bits for a range of 256 shades of each red g
22. istory and is evolving at breakneck speeds Acquiring a solid knowl edge of this history and evolution is as important as keeping up with current trends Kerlow Isaac Victor The Art of 3 D Computer Animation and Imaging New York John Wiley amp Sons 2000 Derakhshani Dariush Introducing Maya 9 3D for Beginners San Francisco Sybex 2008 Kuperberg Marcia Guide to Computer Animation Burlington MA Focal Press 2002 Masson Terrence CG 101 A Computer Graphics Industry Reference Indianapolis New Riders Publishing 1999 Film Block Bruce The Visual Story Seeing the Structure of Film TV and New Media Burlington MA Focal Press 2001 General Myers Dale K Computer Animation Expert Advice on Breaking into the Business Milford MI Oak Cliff Press 1999 Periodicals These magazines offer great topical insights into the industry and product reviews as well as offering some tutorials for further study Computer Graphics World free subscription for those who qualify www cgw pennnet com cinefex www cinefex com HDRI3D www hdri3 D com 3D World www 3 Dwor 1dmag com Websites You ll find a wealth of information at your finger tips at these websites www area autodesk com www animationartist com www awn com www highend3d com www 3dcafe com 30 CHAPTER 1 BASIC CONCEPTS Summary In this chapter you learned the basic concepts that drive the CG field Starting with pro duction workflow
23. less compression and are frequently used for broadcast or video work These formats also have an alpha channel giving you better control when you later composite images together To see an animation rendered in a file sequence of TIFFs you will need to play them back using a frame player such as 3ds Max s RAM Player or you can compile them into a movie file such as a QuickTime file Your final image output format will depend on the project s needs If for example you need to composite your CG together you will need to output in a format that can be used in your compositing or editing program TIFF files are perhaps the best format to use as they are widely compatible store uncompressed color and have an alpha channel MOVIE FILES Animations can also be output to movie files such as AVI or QuickTime These usually large files are self contained and hold all the images necessary for the animation that they play back as frames Like image files movie files can be compressed to keep their sizes to a minimum but they suffer from quality loss as well 3ds Max can render directly to an AVI or QuickTime movie file This may seem like it saves you the hassle of rendering out large sequences of image files In reality you shouldn t render directly to a movie file at least for your final output It is best to render a sequence of files because image sequences can easily be compiled into a movie file later using a program such as Autodesk Comb
24. nd RGB give you different methods to control color allowing you to use the method you prefer All the colors available in 3ds Max from textures to lights are defined as either RGB or HSV values for the best flexibility You can switch from HSV to RGB def inition in 3ds Max at any time CMYK COLOR SPACE A CMYK color wheel is used for print work This is referred to as the four color process Color inkjet printers produce color printouts by mixing the appropriate levels of these inks onto the paper All output from a computer that is RGB based to a printer goes through a CMYK con version as it is being printed For professional print work specially calibrated monitors are used to better preview the CMYK color of an RGB image before it is printed Fortunately only print professionals need to worry about this conversion process because most of it is handled by graphics software to a fairly accurate degree VIEWING COLOR The broadcast standard for North America is called NTSC which stands for National Television Standards Committee Industry folks sometimes refer to the acronym as Never The Same Color calling attention to the fact that the color you see on one TV screen will inevitably look different on another TV The same is true for computer monitors especially flat panel displays Unless made to do so different screens are not calibrated to show the same color the same way so what you see on one screen will display differently on another
25. nd color time make final color decisions about CG shots but they also have to work with live action footage that needs to be altered or affected For example a compositor will need to remove a green screen from behind an actor and place that actor into a virtual rendered set With color correction and other tools at their disposal the compositors must make sure everything looks as though it belongs in the shot In many cases the line between lighter and compositor is blurred and the two specialties can become one Generalists are CG artists who can do everything This is not to say they are the be all and end all of all things CG Many studios and boutiques have short term jobs that are small in scale as compared to a production of the DreamWorks film Madagascar for example When a short turnaround is required you need artists who can take a shot from beginning to end by modeling texturing lighting animating and rendering a scene Gen eralists are more likely to work on commercials for example than feature films Core Concepts CG touches many disciplines and you will come across many different concepts as you learn CG You ll need to understand something about physics computer output film photography sculpting painting and other disciplines This section introduces several key concepts that will make it easier for you to understand how CG is created Again if you ve been around the block a few times you can skip large pa
26. ngine and see what s already available especially at sites such as ww turbosquid com When you model of course you ll be faced with many choices about how to proceed Most Max modeling is done using polygons geometric representations of surfaces and objects however the specific tools you use to create the models will depend on how you like to work The process of modeling can be easier when you have a good idea of your whole story via a storyboard and copiously reference the object you are modeling If you identify your project needs as fully as you can at the outset you ll be able to fulfill them more easily when you start modeling or gathering models With forethought you will know how detailed your models need to be In many cases you can add sufficient detail to a model through texture If a park bench is shown in a wide shot from far away there is no need for abundant detail or complicated surfacing If you create a highly detailed model for that far away shot you will have wasted your time and will also increase your rendering time However if you have to show that park bench prominently in a close up it will need as much detail as possible In such cases viewers will see more of the bench and have more of an opportunity to question it The more you use models in scenes the better you will be at sensing exactly how much detail to give a specific model As you begin with CG however it s better to give too much attention to det
27. nt methods stray a little from the dic tated steps and try your own ideas on for size Ideally you will obtain a stronger educa tion this way but doing so will perhaps be slower and require you to be more patient However getting a good education always requires this sort of dedication What Is CGI In addition to standing for computer graphics CG is sometimes used as an acronym for computer generated You may have heard the term CGI computer generated imagery These terms refer to any image or images that are created with the aid of a computer In this day and age you d be hard pressed to find anyone with any computer experience who hasn t messed around with electronic images such as scanned pictures or digital photos Learning a CG package such as 3ds Max is just an extension of the simple concept of play ing around with a digital photo The obvious differences are that 3ds Max adds the dimen sion of depth as well as control over time Computer graphics is a more common toolset in the hands of the masses than it was just a few years ago Within the next decade or so 3D rendering will be as ubiquitous as Photoshopping a photo is today Artists who are not in the 3D or CG industry are finding that programs such as 3ds Max are valuable tools for generating elements for their own work digital or not Let s take a look at the concepts behind 3D creation The following sections break down the fundamental concepts behind CG 3
28. omes SUBTRACTIVE AND ADDITIVE COLOR Subtractive color mixing is used when an image will be seen with an external light source It s based on the way reflected light creates color Light rays bounce off colored surfaces and are tinted by the different pigments on the surface These pigments absorb and reflect only certain frequencies of the light hitting them in essence subtracting certain colors from the light before it gets to your eyes Pile up enough different colors of paint and you ll get black all the color is absorbed by the pigment and only black is reflected With subtractive color mixing for painting the traditional color wheel s primary colors are red blue and yellow These three pigments can be mixed together to form any other color pigment This is the basis for the color wheel most people are exposed to in art edu cation However in the world of print production a CMYK Cyan Magenta Yellow and blacK color wheel is used which places cyan yellow and magenta ink colors as the pri mary colors used to mix all the other ink colors for print work Projected light however is mixed as additive color Each light s frequency adds upon another s to form color The additive primary colors are red green and blue These three colors when mixed in certain ratios form the entire range of color When all are equally mixed together they form a white light A computer monitor uses only additive color mixing each color with am
29. ook so different from Photoshop s interface Where is the original image that gets altered in 3ds Max Autodesk 3ds Max and other 3D pro grams work with vectors Vectors are created using mathematical algorithms and geo metric functions A vector program defines its images using coordinates and geometric formulas to plot points that define areas volumes and shapes instead of defining the color of each and every pixel in a grid of a raster image Popular vector based image applications include Adobe Illustrator and Macromedia Flash as well as practically all computer aided design CAD programs including Auto CAD and SolidWorks These programs let you define shapes and volumes and add color and texture to them through their toolsets Vector files store the scene in 3D space using coordinates and equations of points in space and the color values are assigned through materials Therefore when a vector image is scaled the image does not suffer from the same blocky limitations as a raster image would As you can see in Figure 1 4 vectors can be scaled with no loss of quality They will never pixelate because they always redraw at the new scale Motion in a raster movie such as a QuickTime movie is stored in a long sequence of image files that when played back show animation or movement By contrast motion in vector programs is stored in the changes in the coordinates of the geometry and in the math that defines the shapes and volumes When
30. or painfully slow The amount of geometry the number of polygons you used to model the number and types of lights the size of texture images and the effects in your scene all affect render times When time or resources are limited you need to build your scene intelligently so that you don t spend hours rendering a single frame The more efficient your scene is the faster the rendering will go Having said that there is really no magic formula to figure out how long is too long for a render Some scenes require a massive amount of time to render for whatever reason and you are stuck with that but most do not In time you ll be able to ascertain for your self how long is too long for your renders A good gauge for render times is to identify what computers you have to render with and how much time you have before a project has to be completed With a little simple math you can determine an acceptable render time for your scenes and adjust your qual ity and output settings as well as your lighting setup to fit within your constraints CG SPECIALTIES 13 The general rule in production is You re always out of time Therefore the most efficient pipeline will be your savior because eventually your producer or boss will tire of hearing But I m still rendering For now go ahead and use as much geometry and lighting as you think is necessary With more experience you ll start pruning your scenes and getting more efficient
31. ounts of red green and blue RGB Output for print is converted to a CMYK color model Warm colors are those in the magenta to red to yellow range and cool colors are those in the green to cyan to blue range of the additive color wheel Warm colors seem to advance from the frame and cool colors seem to recede into the frame HOW A COMPUTER DEFINES COLOR Computers represent all information including color as sets of numeric values made up of binary 0s and 1s bits With a 24 bit RGB color depth each pixel is represented by three 8 bit values corresponding to the red green and blue channels of the image An 8 bit binary number can range from 0 to 255 therefore you have 256 possible levels for each primary color With three channels you have 256 x 256 x 256 16 7 million possible combinations of each primary color mixed to form the final color CORE CONCEPTS 21 Color value need not be expressed in values for red green and blue It can also be set on the hue saturation and value HSV channels of a color Again each channel holds a value from 0 to 255 in an 8 bit image that defines the final color The hue value defines the actual tint from red to green to violet of the color The saturation defines how much of that tint is present in the color The higher the saturation value the deeper the color Finally value defines the brightness of the color from black to white The higher the value the brighter the color HSV a
32. our scene will probably look different when you light and animate everything You ll learn more about texturing in Chapter 7 Materials and Mapping Animation Animation puts your scene into action and adds life to your characters Animation is change over time Anything in a scene that needs to change from one second to another will need to be animated to do so Everyone has their own reflexive sense of how things move This knowledge is gleaned through years of perception and observation Therefore your audience can be more criti cal of a CG scene s motion than lighting coloring or anything else You know when some thing doesn t look right So will your audience Animation takes quite a lot of setup sometimes more than just modeling For a charac ter you will need to create a rig a character s setup or digital armature used to drive char acter animation such as a Character Studio Biped to attach to the model and then create controls to make animation easier to operate It s thrilling to see your hard work on a scene come to life with animation On the flip side it can be extremely aggravating to see your creation working improperly Making mistakes is how you learn things and your frustrations will ease over time Your first sev eral attempts at animating a scene will not look like Pixar films but that should not dis suade you from working on more animations and scenes You will get better with more practice Chapter
33. reen and blue channel A total of 16 million colors are available to use in the image This color depth gives the best color quality for an image and is widely used in most animation applications The human eye cannot see quite as many shades of color as there are in a True Color image Most of your renders from 3ds Max will be 24 bit color files 16 Bit Image File Used primarily in film work using such file types as TIFF16 this type of image file holds 16 bits of information for each color channel resulting in an astounding number of color levels and ranges Each file can exceed several megabytes even at low res olutions These files are primarily used in the professional workplace and are more stan dard for film work because outputting CG to film can require high levels of color and brightness range in the image Floating Point 32 Bit Image File Thirty two bit floating point images are commonly used in film production to give the utmost attention to color depth Most computers are capable of rendering a huge range of tones and colors and 32 bit floating point images capture that range effectively These files such as EXR and HDR images are not easy to work with and require a lot of tweaking in compositing to output properly EXR based on the OpenEXR format pioneered by Industrial Light and Magic for high end film work and High Dynamic Range HDR images are usually in 32 bit float format and are incredibly detailed in the range of contrast
34. renders Right now knowing how a scene is put together is more important than knowing how efficient it needs to be CG Specialties As in most professions CG professionals specialize in specific areas Those areas coincide with the stages of CG production outlined earlier in this chapter Modelers create models for shows or projects They need to have a keen eye for detail as well as a sense of how objects come together Environment modelers create settings and character modelers specialize in creating organic surfaces for characters such as peo ple In all cases professional modelers need to understand form and function and be expe rienced in lighting rendering and texturing to effectively model professionally Animators are artists who work directly with the animation of a project Character ani mators specialize in character movement ranging from mimicking human movement to outlandish cartoon animation There are also animators who specialize in mechanical objects Frequently good animators can span the divide between character animation and other types of animation because they inherently understand motion and timing In some cases great animators are also great riggers Studios hire character TDs tech nical directors who specialize in rigging characters for motion This usually includes cre ating skeleton structures such as Bipeds or Bones for the character as well as skinning the model to such a system before handing it off to
35. rfaces and models in a scene Props Modeling A prop is any object in a scene that is actively used by a character in his or her action Props are useful to the narrative of the story They help the characters actions A prop can be anything from a baseball bat that a character is swinging to a purse that a character is carrying Any objects not used by the characters as props are called scenics as they are often used to add realism to the set by setting the scene Think about it If your scene takes place in front of a desk that desk will need scenics such as pens notebooks and papers to make it look more realistic Just showing an empty desk may not be enough to make the scene believable You usually can find the props and scenics you need on the Internet frequently in a format for 3ds Max Texturing Once you have created a model you ll want to finish its look You can apply materials to its surface s to make it look right whether it is supposed to look real or not Texturing is typically applied immediately after modeling and heavily tweaked when the scene is lighted The process of texturing essentially applies colors and tactile feeling to models 3ds Max automatically assigns simple colored materials to objects as you create them CG WORKFLOW 11 You don t need to finalize every texture at the beginning because you ll be coming back and making adjustments all the time Remember that the materials you create for y
36. rself once she lands You can also create a small amount of movement before your action is in full swing Before committing to an action a character may wind up to a greater or lesser extent Doing so will create a slight anticipation in the movement for example a hammer cock ing back slightly before it strikes or a cartoon superhero that bends down before he jumps up to fly away These concepts are covered in Chapter 8 Basic 3ds Max Terms and Concepts Any 3D program has terms and concepts you need to learn to become a good artist in that tool Most of these concepts are fairly transferable meaning they apply to more than one CG package although their names may vary depending on which package you are using Here are several terms and concepts you will encounter in the world of CG as they relate to 3ds Max If you are not already familiar with 3ds Max s interface running through this list before diving into the next chapter might be a good idea Objects An element in your 3ds Max scene is called an object An object may be converted to a more easily editable mesh at any time You will learn about this concept in Chapter 4 Modeling in 3ds Max Part I Primitives Primitives are basic Max objects such as spheres or boxes Primitives can be shaped and altered to suit the needs of the model Sub objects Many though not all objects are made up of components called sub objects You can select and manipulate sub objects in 3ds Ma
37. rt whether it s your own drawings or photos or images grabbed from the Internet you are in trouble You must have an idea of how you want your CG to look otherwise you are just burning calories and not saying i Figure 1 2 anything A character sheet If you have CG characters create character sheets for each character that show them in three different neutral poses from the front from the side and from an angle called a view You can even sculpt reference characters in clay or Play Doh if you need to have a better idea of how they should look in 3D space In Figure 1 2 you can see a character sheet gener ated for a student produced short at The Art Institute of California at Los Angeles 6 CHAPTER 1 BASIC CONCEPTS Sketch or download images of the props and sets you need in your scene You should map out the look for everything that you need to have in your scene When you are working on your project you won t be limited to the things you picked out at this stage however you will find that knowing how things should look will help enormously in get ting you to your final product The better your concept art and research the smoother the production and the better your end result will be Production Production is the meat of any project Film production begins when you start filming your project In the case of CG production begins when you start creating assets for your proj ects such as models or texture
38. rts of this chapter How ever you never know when you might come across a little tidbit that fills in an educational gap you never thought you had Computer Graphics Basics Here are some general terminologies and methodologies used in computer graphics Understanding them will help you understand how 3ds Max works First on our plate is the critical distinction between raster bitmap and vector graphics and how this distinc tion affects you as a 3ds Max user Raster Images Raster images also known as bitmap images or bitmaps make up the world of computer images today In raster images colored pixels are arranged to display an image on a screen these pixels come together to form the image like a tapestry The same is true of printouts where dots of ink serve as pixels to form the printed image The printed dots like each colored pixel come together to form the overall image When you work in a program such as Photoshop you are editing the pixels of an image directly by adjusting existing settings such as color size and position for all or part of an image In this manner you can bring a scanned photo or a digital picture of your house into Photoshop and paint one wall red just to see how it would look before you buy paint at the store Essentially a raster or bitmap image is a mosaic of pixels each pixel corresponding to a mosaic tile The resolution fineness of detail of an image is defined by the number of pixels per inch
39. rything else is done and you are left to go back and forth with the render to check and recheck fix and refix issues that come up in the rendered images You may even find for example that a model you ve built needs to be altered because a lighting scheme works for everything but that model Therefore a back and forth workflow with lighting does not just apply to texturing The more experience you gain with lighting the more you will start to notice that light ing affects every stage of CG creation Once you start mastering the subtleties of lighting and after years of modeling you may change how you model to accommodate how you now light Even your animation and texturing preferences may take a back seat to how a scene needs to be lighted CG is fundamentally all about light Manipulating how light is created and reflected is what you re doing with CG Luckily in 3ds Max lighting is set up to mimic the behavior of real lights used in live action at least in principle making the lighting process easier to use You will learn how to light in 3ds Max in Chapter 10 3ds Max Lighting Rendering You ve modeled it all textured it and lit your scene like a pro Hundreds of hours and several cases of Red Bull later you are ready to render Rendering is the stage where your computer makes all the computations necessary to create images from your 3D objects Depending on how much stuff is in your scene rendering may be super quick
40. s based on well researched reference materials The produc tion phase lasts until the rendering phase where you actualize your scene into image files Animation texturing and lighting are all performed between the modeling and ren dering phases Later in this chapter we ll divide the CG production phase into more stages however most of the techniques you ll learn in this book are components of the production phase Postproduction Postproduction begins when your scene elements and animation are all set up and raring to be completed Postproduction for a CG project is very similar to postproduction for a film When you click the Render button you ll end up with several image files or movie files that are then edited and put together to make your project You add sound correct color combine elements and add any finishing touches in postproduction Here is a quick rundown of the CG postproduction pipeline Rendering All CG scenes need to be rendered to their final image or movie files Again this is the process by which the computer calculates how everything in the scene should look and displays it Rendering makes your computer work hard It usually requires the full atten tion of your PC and can take a lot of time As you ll learn throughout this book the deci sions you make such as how much detail you give the objects you create for a scene can make a big difference in the rest of the process and can affect the rendering speed
41. s and create its intended look on the first try This is not the case CG has an inherently modular nature You can render items separately and composite them in the finishing stage while retaining the ability to make changes in the project without rendering everything again Rendering a proj ect in different layers sometimes called passes also gives you much greater control over the project s look Editing During editing rendered and composited CG footage is collected and edited to fit the script and storyboards This process is usually more straightforward for a CG film than for a live action movie provided that you made good storyboards during preproduction to follow when assembling the finished film With live action shoots you shoot much more footage than will ultimately end up in the film You do this to make sure you have enough material for all your scenes and to leave extra room for creative editing Additionally you have to run through all the footage and choose which takes will be in the final product Because CG footage is generally much more time consuming to generate than live action scenes and shots should be tightly arranged in preproduction storyboards The entire production can be edited beforehand in storyboards so the scenes that are built and animated can match the story almost down to the frame If your preproduction was done well it can be just a matter of putting the shots together using an editing program such as A
42. s are displayed 1 85 1 as seen below Widescreen Film 1 85 1 The most often used 35mm film aspect today aka Academy Flat When it s displayed on a television horizontal black bars appear above and below the picture so that the edges are not cropped off This is called letterboxing Anamorphic Ratio 2 35 1 Using a special lens called an anamorphic lens an image originally captured on 35mm film is squeezed When played back with a projector with an anamorphic lens the image is projected at a width 2 35 times its height On a standard TV the letterboxing would be more severe to avoid cropping the sides The number of frames that are played back per second determines the frame rate of an animation This is denoted as fps or frames per second The three standard frame rates for media are NTSC 30fps PAL 25fps Film 24fps Knowing what your final output medium is going to be before you begin your project is pretty important It is not crucial by any means but knowing what the screen will look like i e whether it will be a small web window or a large television will help you better compose your scenes You can always change your frame rate and render resolution later but it is much simpler to begin with it already worked out Playing back a 24fps animation at 30fps will yield a slower moving animation and will either require repeating some frames to fill in the gaps or ending the animation early Conversely playing a
43. screen If it is paramount that the color appear as you see it on a specific screen it makes sense to finalize the work and show it on that screen You can also download color bars from the Internet to display on monitors in an attempt to calibrate them to your eye This is not the best way to go but at least it will help a little without exacting the costs and trouble of using color calibration equipment Resolution Aspect Ratio and Frame Rate Resolution expresses the size of an image by the number of horizontal and vertical pixels it contains and usually is stated as x x y an example of this would be 640 x 480 The higher the resolution the finer the image detail will be You will adjust your final render size to suit the ultimate medium for which you are creating the animation Table 1 1 lists some typical video resolutions 22 CHAPTER 1 BAsIC CONCEPTS Table 1 1 STANDARD SIZE NOTES Typical Video VGA Video Graphics Array 640 x 480 Formerly the standard computing resolution and Resolutions still a popular television resolution for tape output NTSC D1 National Television 720 x 486 The standard resolution for broadcast television in System Committee North America NTSC DV 720 x 480 Close to the NTSC D1 resolution this is the typical resolution of digital video cameras PAL Phase Alternation Line 720 x 586 The standard broadcast resolution for most Euro pean countries HDTV High Definition TV 1920 x 1080
44. they store You should not worry about 32 bit images and high dynamic ranges such as this until you have gained a good amount of experience with lighting and rendering Color Channels As mentioned each image file holds the color information in channels All color images have a red green and blue color channel Each channel is a measurement of the amount of red green or blue in areas of the image A fourth channel called the alpha channel is used as a transparency channel This channel also know as the matte channel defines which portions of the image are transparent or opaque Not all image files have alpha channels CORE CONCEPTS 19 FILE FORMATS In addition to image types several image file formats are available today The most com mon is probably JPEG Joint Photographic Experts Group which is widely used on the Internet for its small size and reasonable image quality However JPEGs are too com pressed and lossy meaning they lose color detail when compared to the original to be used in most CG renders The main difference among file formats relates to how they store images Some formats compress the file to reduce file size however the greater the compression the poorer the image s color The popular formats to render into from 3ds Max are TIFF Tagged Image File For mat and Targa TGA These file formats maintain a good 24 bit color depth using an 8 bit image file are either uncompressed or hardly compressed loss
45. uilt to account for differences in detail level Using dif ferent versions of the same character can help keep the scene efficient and workable A CG WORKFLOW 9 10 CHAPTER 1 BASIC CONCEPTS low resolution model of a character one that uses few polygonal faces can easily be placed in wide shots and a more detailed higher resolution model can be used in close ups Architectural and Environmental Modeling 3ds Max is a natural tool for architectural and environmental modeling In fact architects and engineers use it to model and render designs for previsualizing This type of modeling includes the generation of backgrounds for sets and environments To do this you model any buildings or interiors as well as mountains and other required scenery such as trees roads lampposts and mailboxes Do not create overly detailed environments when they are far off in the background The biggest common mistake new CG practitioners make is over creating detail Doing this adds more geometry to a scene creates inefficiency and can crash a scene The more geometry that is used in a scene the more slowly the computer will run and the more time you will need to render the scene You can create a good deal of the environment using clever textures on simple geometry Detailed maps on bare surfaces are used frequently for game environments Because your computer stores everything in a scene as vector math the term geometry refers to all the su
46. ustion Adobe After Effects Premiere or even QuickTime Pro Rendering to images is less risky than rendering to a movie In addition to having a sequence you can easily manipulate you do not have to worry about crashing and losing rendering time Sometimes your render will crash or your machine will freeze If you are rendering to a movie file when that happens you ll need to restart rendering from the beginning because you can t append content to a half rendered QuickTime With a file sequence render you can simply pick up the render from the last good frame With a sequence you also have the option of reordering the frames or easily adjusting a few individual frames properties such as hue or saturation without affecting the entire movie file 20 CHAPTER 1 BASIC CONCEPTS Color Color is how we perceive the differences in the frequency of light The wide range of colors that we see the visible spectrum results when any of three primary colors of light red green and blue are mixed together Color can be mixed in two ways subtractive and additive These color definitions are most often displayed in color wheels which place pri mary colors equally spaced around a ring and place the colors that result when the primar ies are mixed in between the appropriate primaries Understanding how color works will help you gain more from your CG s color scheme and help you design your shots with greater flexibility and better outc
47. vastly different from those of live action photog raphy understanding this framework is useful to understanding CG Preproduction Preproduction for a CG workflow requires that the artist or artists gather together all the reference materials motion tests layout drawings model sketches and other components to make the actual CG production as uncomplicated as they can Because everything is essentially made from scratch you have to formulate a strong plan of attack You can t just take some actors into the park and begin shooting With CG you have to make it all from nothing or at least acquire assets such as models from places such as TurboSquid com The time spent in preproduction planning is vital to smooth production and postproduction and it helps the overall outcome of the project Never underestimate how much time and planning you should put into a CG project You will seriously sandbag your project if you don t plan it effectively Although you may get sick of hearing this it will always be true As you do the exercises in this book you will work with sketches and other files sup plied on the accompanying CD These are your preproduction assets Additionally you are strongly encouraged to put together as much information as you possibly can about your intended project no matter how short it may seem A poorly planned production will always fall short of its potential and give you many headaches throughout your project
48. x to alter the look or function of an object Kinds of sub objects include vertices faces polygons edges gizmos and centers The types of sub object you are able to manipulate depend on the type of object you are manipulating See Chapter 4 for more on sub objects Normals Each face of a polygon has a direction in which it points A normal is a vector that defines which way a face points Spinners Spinners are a function of the user interface UI in Max Spinners are the little i just th arrows to the right of value readouts they allow you to adjus iz oo values by clicking up or down on them A spinner for a sphere s radius value is shown here Flyouts Another UI term a flyout is an icon in 3ds Max that is actually several icons in one If you press and hold a flyout icon the other icons fly out and display themselves Scroll to the icon you need and click to activate its flyout properties A flyout icon has a black triangle in its lower right corner as here Flyouts are further covered in Chapter 3 The 3ds Max Interface 28 CHAPTER 1 BASIC CONCEPTS Figure 1 7 The Home Grid in the Perspective viewport y x lie Home Grid The Home Grid is a gray grid that displays the origin 0 0 0 It is useful for grounding yourself in the viewports and it helps with proportion and direction as well A Perspective viewport Home Grid is shown in Figure 1 7 Absolute Relative Absolute refers to an
49. your photos Knowing what the end result should be will dictate how you decide to render You can choose several settings for quality and output for example so you can show off your scene to your friends although a QuickTime movie can t be hung on the fridge the way a photo can WHAT IS CGI 3 Figure 1 1 3D space looks good enough to eat 4 CHAPTER 1 BASIC CONCEPTS Of course with CG you also have control over time because you can animate your scene The workflow we ll discuss in this chapter is best illustrated with a film production example The next section will briefly describe a film production workflow and how it relates to CG production Production Workflow There are three major stages to producing films preproduction production and postpro duction In preproduction the script is written storyboards are drawn up to outline the action costumes and sets are designed and built the actors are cast and prepared and a production crew is put together During the production phase the scenes are set up and shot according to a production schedule that lays everything out in the most efficient manner possible Finally in postproduction everything else happens The film is printed and edited a score and soundtrack are laid any digital effects are added and scenes are colored to match an overall aesthetic When all of this is finished the film is distributed for people to see Although the specific tasks of CG are
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