Animation

IntroductionWe are going to study how things move and the creation of computer graphics representations that look good enough

Rendering is: mapping light sources and surfaces to a vector of pixel colorsAnimation is: mapping objects, intentions, and external forces to a vector of new object positions / orientations

We will notDevelop drawing skillsbut we may study how others draw so we can automate the processLearn how to use Mayabut we may use Maya as a rendering toolHone our video game or moviemaking skillsbut we will study how modern animation technology contributes to video games and what elements of moviemaking artistry (timing, camera angles, etc.) must reside in animation tools

Study how things moveWho else does this?

Study how things moveWell investigateHuman walking, running, dancingBicycle ridingGroup behaviorsRigid body dynamics

Generate graphics that is good enoughWho else studies this?Perceptual psychologistsArtistsPicasso The Bull (1946)Monet La Cathdrale de Rouen (1894)University of Utah

Generate graphics that is good enoughWell investigateRecent perceptual literature (change blindness)Recent computer animation experiments (faking physics)

Completing the mappingBridge gap between knowledge of how things move to how they need to be renderedArtists use their minds and handsComputer scientists use math and programs

Traditional techniquesKeyframing (Shoemake)Orientation reps (quaternion, euler)Curve reps (linear, quadratic, wavelets)Interpolation (computing arclength, Gaussian Quadrature, SLERP)Disney artists (Johnson)Timing / storyboarding

Numerical MethodsCurve fitting (least squares)Optimization Simulated annealing (Numerical Recipes)SimplexSpacetime Constraints (Witkin & Kass)Genetic Algorithms (Sims)Neural Networks (Grzeszczuk)

Human MotionMotion CaptureRetargeting (Gleicher, J. Lee, Z. Popovic, Arikan)Blending (Rose)Abstraction (Unuma)WalkingBiomechanics (McMahon, Ruina)Gait Generation (Metaxas, van de Panne, Hodgins)

Physical SimulationRigid BodyPhysics for games (Hecker)Featherstones MethodConstraint satisfactionIntegrationRunge-KuttaEulerSimplification (Chenney, Lin, Popovic)Perception (OSullivan, Proffitt)

Autonomous AgentsBehaviors (Thalmann, Badler, Blumberg)Group actions (Reynolds, Brogan, Helbing)

PerceptionPositive afterimage (persistence of vision)the visual stimulus that remains after illumination has changed or been removedMotion blurPersistence of vision causes an object to appear to be multiple places at once

Motion BlurVirtual camera in computer graphics usually shoots with infinitely small shutter speedNo motion blur resultsWithout motion blur, 30 fps results in fast moving objects that look like they are strobing, or hopping

Whats the rate?Playback rateThe number of samples displayed per secondSample rateThe number of different images per second

Playback RateSample RateTV Cartoon306TV Sitcom3030 (on fields)CG Lipsync on film2412

PerceptionComputer graphics rendering can rely on four-hundred years of perception research by artistsThe best animators have is eighty years of Disney

In 1550, after 100 years of refining the art of perspective drawing, artists were shocked to think that the geometric purity of their modeled world didnt map to recent discoveries of the human eye. They couldnt even imagine how cognition affected what one saw. 200 more years would pass.

Animation timelinePersistence of visionThaumotrope (1800s)FlipbookZoetrope (1834)Shadow puppetspbsKids

Animation timelinePhotographyMuybridge (1885)

Film projector (Edison, 1891)

Animation TimelineFirst Animation1896, Georges Melies, moving tables1900, J. Stuart Blackton, added smokeFirst celebrated cartoonistWinsor McCayLittle Nemo (1911)Gertie the Dinosaur (1914)

Animation Timeline1910, Bray and HurdPatented translucent cels (formerly celluloid was used, but acetate is used now) used in layers for compositingPatented gray-scale drawings (cool!)Patented using pegs for registration (alignment) of overlaysPatented the use of large background drawings and panning camera

Brays Studio ProducedMax Fleischer Betty BoopPaul Terry TerrytoonsGeorge Stallings Tom and JerryWalter Lantz Woody Woodpecker

1915, Fleischer patented rotoscopingDrawing images on cells by tracing over previously recorded live action (MoCap)1920, color cartoons

DisneyAdvanced animation more than anyone elseFirst to have sound in 1928, Steamboat WillieFirst to use storyboardsFirst to attempt realismInvented multiplane camera

Multiplane CameraCamera is mounted above multiple planesEach plane holds an animation celEach plane can translate freely on 3 axesWhat is this good for?Zooming, moving foreground characters off camera, parallax, prolonged shutter allows blurring some layers (motion blur)

Stop-motion AnimationWillis OBrien King KongRay Harryhausen Mighty Joe YoungNick Park Wallace and GrommitTim Burton Nightmare Before Christmas

Animation Heritage1963 Ivan Sutherlands (MIT) Sketchpad1970 Evans and Sutherland (Utah) start computer graphics program (and Co.)1972 Ed Catmulls (Utah) animated hand and face (later co-founded Pixar)1970s Norm Badler (Penn) Center for Modeling and Simulation and Jack

Animation Heritage1970s New York Institute of Technology (NYIT) produced Alvy Ray Smith (Cofounded Pixar and Lucasfilm) and Catmull1980s Daniel and Nadia Magnenant-Thalmann (Swiss Universities) become European powerhouses

Animation Heritage1980s z-buffer invented, SGI founded, and Alias/Wavefront founded1977 Starwars1982 Tron (first extensive use of gfx)1982 Early use of particle systems (Star Trek II: The Wrath of Khan)1984 The Last Starfighter (look for the Cray X-MP in credits)

Animation Heritage1986 Young Sherlock Homes (first use of synthetic character in film) 1986 First digital wire removal (Howard the Duck)1988 First digital blue screen extraction (Willow) The Abyss (1989) Terminator II (1991) Casper (1995), Men in Black (1997)

Animation HeritageILM: Jurassic Park (1993), Jumangi (1995), Mars Attacks (1996), Flubber (1997), Titanic (1999)Angel Studios: Lawnmower Man (1992)PDI: Batman Returns (1995) Tippett Studio: Dragonheart (1996), Starship Troopers (1997)Disney: Beauty and the Beast (1991), Lion King (1994), Tarzan (1999)Dreamworks: Antz, Prince of EgyptPixar: Toy Story, A Bugs Life, Monsters Inc.

Americans are hardest workingRecent historyUnited Nations report from Sept 1, 2003$/worker-yearUS = $60,728, Belgium (top EU) = $54,333hours/worker-yearUS = Japan = 1825, EU = 1300 1800$/worker-hourNorway, France, Belgium, US $38 $35 $34 $32Why is US on top of $/worker-year?Best economies encourage widespread use of communications and information technologyEven though were fat, dumb, and happy we dont take month-long vacations and one-year maternity breaks

Lets talk about computer animationMust generate 30 frames per second of animation (24 fps for film)Issues to consider:Is the goal to replace or augment the artist?What does the artist bring to the project?Is the scene/plot fixed or responsive to user?What can we automate?

Animation A broad BrushTraditional MethodsCartoons, stop motionKeyframingDigital inbetweensMotion CaptureWhat you record is what you getSimulationAnimate what you can model (with equations)

Computer Animation

KeyframingTraditional animation techniqueDependent on artist to generate key framesAdditional, inbetween frames are drawn automatically by computer

KeyframingFrom The computer in the visual arts, Spalter, 1999How are we going to interpolate?

Linear InterpolationSimple, but discontinuous velocity

Nonlinear InterpolationSmooth ball trajectory and continuous velocity, but loss of timing

EasingAdjust the timing of the inbetween frames. Can be automated by adjusting the stepsize of parameter, t.

Style or Accuracy?Interpolating time captures accuracy of velocitySquash and stretch replaces motion blur stimuli and adds life-like intent

Traditional MotivationEase-in and ease-out is like squash and stretchCan we automate the inbetweens for these?The Illusion of Life, Disney AnimationThomas and Johnson

More squash and stretch

Anticipation and StagingDont surprise the audienceDirect their attention to whats important

Follow ThroughAudience likes to see resolution of actionDiscontinuities are unsettling

Combined

Secondary MotionCharacters should exist in a real environmentExtra movements should not detract

InterpolationMany parameters can be interpolated to generate animationSimple interpolation techniques can only generate simple inbetweensMore complicated inbetweening will require a more complicated model of animated object and simulation

InterpolationStrengthsAnimator has exacting control (Woodys face)WeaknessesInterpolation hooks must be simple and directRemember the problems with Euler angle interp?Time consuming and skill intensiveDifficult to reuse and adjust

ExamplesSports video gamesMadden FootballMany movie charactersPhantom MenaceCartoons

Motion Capture StrengthsExactly captures the motions of the actorMichael Jordans video game character will capture his styleEasy to capture data

Motion Capture WeaknessesNoise, noise, noise!Magnetic system inteferenceVisual system occlusionsMechanical system massTethered (wireless is available now)

Motion Capture WeaknessesAligning motion data with CG characterLimb lengthsIdealized perfect jointsFoot slidingReusing motion dataDifficult to scale in size (must also scale in time)Changing one part of motion

Motion Capture WeaknessesBlending segmentsMotion clips are short (due to range and tethers)Dynamic motion generation requires blending at run timeDifficult to manage smooth transition

Proceduralwww.sodaplay.comhttp://jet.ro/dismount

ExamplesInanimate video game objectsGT Racer carsSoapbox about why this is so coolSpecial effectsExplosions, water, secondary motionPhantom Menace CG droids after they were cut in half

Procedural AnimationVery general term for a technique that puts more complex algorithms behind the scenesTechnique attempts to consolidate artistic efforts in algorithms and heuristicsAllows for optimization and physical simulation

Procedural Animation StrengthsAnimation can be generated on the flyDynamic response to userWrite-once, use-oftenAlgorithms provide accuracy and exhaustive search that animators cannot

Procedural Animation WeaknessesWere not great at boiling human skill down to algorithmsHow do we move when juggling?Difficult to generateExpensive to computeDifficult to force system to generate a particular solutionBicycles will fall down

Fundamental Animation Techniques

Fundamental Animation TechniquesSquash and StretchTimingAnticipationStagingSlow In and Slow OutArcsExaggerationSecondary ActionAppealPersonality

Squash and Stretch

More squash and stretch

Timing is everything!

TimingTiming = speed of actionRelays the idea behind the actionToo fast: might not notice at allMight not understand whats happenedmight not pay enough attentionToo slow: Sense of action can be lostcan become boring

TimingDefines weight of the objectHeavy objects accelerate slowlySize in general should correspond to the massShows emotional stateIdentical key frames can have different timing

Timing exampleTwo key framesHead leaning toward the right shoulderHead over left shoulder, chin slightly raisedVary the number of in-between frames, 0 to 10Very different ideas can be communicated

Timing example, cont.0: hit by tremendous force1: hit by a brick, frying pan2: nervous tick, muscle spasm3: dodging a brick, frying pan4: giving a crisp order Move it !5: friendly Over here. Come on - hurry6: sees a sports car he always wanted7: tries to get a better look at something.8: searches for a book on a shelf9: appraises, considering thoughtfully10: stretches a sore muscleExample from: Thomas and Johnson Disney animation the illusion of life

Anticipation

AnticipationAction has three partsPreparation for the action (anticipation)Action itselfTermination of the action (follow through)Need anticipation to:Make actions naturalMuscle movement (kicking a ball)Prepare audience for the following actionDirect attention to another part of the screen

AnticipationSlow action: can use little anticipationMeaning is carried by the action itselfFast action: need more anticipationNeed to know whats going to happen even before the actionExaggerated anticipation:Emphasize extreme weight / action difficulty

Staging

Follow-Thru and Overlapping Action

Follow throughActions rarely come to sudden stopsThere are leading parts, other participating parts and appendagesAction starts by leading partMain action followsAppendages continue to move longerHeavy ones drag along longer

Follow ThroughAudience likes to see resolution of actionDiscontinuities are unsettling

Overlapping actionAdd variations to timing of loose partsLittle extra actions make it more interestingNew action starts BEFORE previous one stopsFull stops are rarelocking open door:Start walking to the doorBefore coming to the door, reach for the doorBefore completely closing, reach for the key, etc.

Slow in and slow outEven spacing between frames = constant speedBetter to have gradual acceleration and slowing down

Bouncing Ball ExampleThe ball on the left moves at a constant speed with no squash/stretch. The ball in the center does slow in and out with a squash/stretch.The ball on the right moves at a constant speed with squash/stretch.

ArcsVisual path should be an arcRather than a straight line

Exaggeration and secondary actionKeep it balancedHave some natural elements and some exaggerated onesSecondary action results directly from primary actionGives natural complexityCan be missed if happens in the middle of major moveShould be obvious but kept secondaryThe secondary action of Luxo Jr's forward motion is the rippling of his power cord.

Exaggeration

Secondary Action

Appeal & Personality

Basic Camera ShotsWide Shot/Establishing Shot/Long ShotMedium ShotClose Up ShotCutaway Shot/Over the ShoulderTwo Shot/Three ShotSequenceLength of shot

Wide Shot/Establishing

Medium Shot

Close Up Shot

Extreme Close Up

Two Shot/Three Shot

Cutaway Shot Cutaway (CA)A cutaway is a shot that's usually of something other than the current action. It could be a different subject (eg. this cat when the main subject is its owner), a close up of a different part of the subject (eg. the subject's hands), or just about anything else.The cutaway is used as a "buffer" between shots (to help the editing process), or to add interest/information.

Basic Camera MovesZoom InZoom OutPan Right, Pan LeftAction in the frame.Follow the action/rolling shot.

Standard Movie OpeningsMovie Opening 1Wide ShotZoom to MediumSome Action.Zoom to close-upOut to Medium.Most Bond FilmsMovie Opening 2Tight Close-UpOut to MediumActionZoom to close-upOut to MediumRun with it.Raiders of Lost Ark

Just two drawings of a head, the first showing it leaning toward the right shoulder and the second with it over on the left and its chin slightly raised, can be made to communicate a multitude of ideas, depending entirely on the timing used. Each in-between drawing added between these two extremes gives a new meaning to the action. NO inbetweens - The Character has been hit by a tremendous force. His head is nearly snapped off ONE inbetween - The Character has been hit by a brick, rolling pin, frying pan TWO inbetweens - The Character has a nervous tic, a muscle spasm, an uncontrollable twitch THREE inbetweens - The Character is dodging a brick, rolling pin, frying pan FOUR inbetweens - The Character is giving a crisp order, "Get going!" "Move it!" FIVE inbetweens - The Character is more friendly, "Over here." "Come on-hurry!" SIX inbetweens - The Character sees a good looking girl, or the sports car he has always wanted SEVEN inbetweens - The Character tries to get a better look at something EIGHT inbetweens - The Character searches for the peanut butter on the kitchen shelf NINE inbetweens - The Character appraises, considering thoughtfully TEN inbetweens - The Character stretches a sore muscle Establish the settingNarrate the storySay something importantSay something extremely important and dramatic.Narrate the storyConnect the scene to the audience.