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Animation

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Title: Introduction to Computer Graphics CS 445 / 645 Author: David Brogan Last modified by: Retestrak Created Date: 8/29/2002 6:32:11 PM Document presentation format – PowerPoint PPT presentation

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Title: Animation


1
Animation
2
Introduction
  • We 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 colors
  • Animation is mapping objects, intentions, and
    external forces to a vector of new object
    positions / orientations

3
We will not
  • Develop drawing skills
  • but we may study how others draw so we can
    automate the process
  • Learn how to use Maya
  • but we may use Maya as a rendering tool
  • Hone our video game or moviemaking skills
  • but 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

4
Study how things move
  • Who else does this?

5
Study how things move
  • Well investigate
  • Human walking, running, dancing
  • Bicycle riding
  • Group behaviors
  • Rigid body dynamics

6
Generate graphics that is good enough
PicassoThe Bull (1946)
MonetLa Cathédrale de Rouen (1894)
  • Who else studies this?
  • Perceptual psychologists
  • Artists

University of Utah
7
Generate graphics that is good enough
  • Well investigate
  • Recent perceptual literature (change blindness)
  • Recent computer animation experiments (faking
    physics)

8
Completing the mapping
  • Bridge gap between knowledge of how things move
    to how they need to be rendered
  • Artists use their minds and hands
  • Computer scientists use math and programs

9
Traditional techniques
  • Keyframing (Shoemake)
  • Orientation reps (quaternion, euler)
  • Curve reps (linear, quadratic, wavelets)
  • Interpolation (computing arclength, Gaussian
    Quadrature, SLERP)
  • Disney artists (Johnson)
  • Timing / storyboarding

10
Numerical Methods
  • Curve fitting (least squares)
  • Optimization
  • Simulated annealing (Numerical Recipes)
  • Simplex
  • Spacetime Constraints (Witkin Kass)
  • Genetic Algorithms (Sims)
  • Neural Networks (Grzeszczuk)

11
Human Motion
  • Motion Capture
  • Retargeting (Gleicher, J. Lee, Z. Popovic,
    Arikan)
  • Blending (Rose)
  • Abstraction (Unuma)
  • Walking
  • Biomechanics (McMahon, Ruina)
  • Gait Generation (Metaxas, van de Panne, Hodgins)

12
Physical Simulation
  • Rigid Body
  • Physics for games (Hecker)
  • Featherstones Method
  • Constraint satisfaction
  • Integration
  • Runge-Kutta
  • Euler
  • Simplification (Chenney, Lin, Popovic)
  • Perception (OSullivan, Proffitt)

13
Autonomous Agents
  • Behaviors (Thalmann, Badler, Blumberg)
  • Group actions (Reynolds, Brogan, Helbing)

14
Perception
  • Positive afterimage (persistence of vision)
  • the visual stimulus that remains after
    illumination has changed or been removed
  • Motion blur
  • Persistence of vision causes an object to appear
    to be multiple places at once

15
Motion Blur
  • Virtual camera in computer graphics usually
    shoots with infinitely small shutter speed
  • No motion blur results
  • Without motion blur, 30 fps results in fast
    moving objects that look like they are strobing,
    or hopping

16
Whats the rate?
  • Playback rate
  • The number of samples displayed per second
  • Sample rate
  • The number of different images per second

Playback Rate Sample Rate
TV Cartoon 30 6
TV Sitcom 30 30 (on fields)
CG Lipsync on film 24 12
17
Perception
  • Computer graphics rendering can rely on
    four-hundred years of perception research by
    artists
  • The 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.

18
Animation timeline
  • Persistence of vision
  • Thaumotrope (1800s)
  • Flipbook
  • Zoetrope (1834)
  • Shadow puppets

pbsKids
19
Animation timeline
  • Photography
  • Muybridge (1885)
  • Film projector (Edison, 1891)

20
Animation Timeline
  • First Animation
  • 1896, Georges Melies, moving tables
  • 1900, J. Stuart Blackton, added smoke
  • First celebrated cartoonist
  • Winsor McCay
  • Little Nemo (1911)
  • Gertie the Dinosaur (1914)

21
Animation Timeline
  • 1910, Bray and Hurd
  • Patented translucent cels (formerly celluloid was
    used, but acetate is used now) used in layers for
    compositing
  • Patented gray-scale drawings (cool!)
  • Patented using pegs for registration (alignment)
    of overlays
  • Patented the use of large background drawings and
    panning camera

22
Brays Studio Produced
  • Max Fleischer Betty Boop
  • Paul Terry Terrytoons
  • George Stallings Tom and Jerry
  • Walter Lantz Woody Woodpecker
  • 1915, Fleischer patented rotoscoping
  • Drawing images on cells by tracing over
    previously recorded live action (MoCap)
  • 1920, color cartoons

23
Disney
  • Advanced animation more than anyone else
  • First to have sound in 1928, Steamboat Willie
  • First to use storyboards
  • First to attempt realism
  • Invented multiplane camera

24
Multiplane Camera
  • Camera is mounted above multiple planes
  • Each plane holds an animation cel
  • Each plane can translate freely on 3 axes
  • What is this good for?

Zooming, moving foreground characters off camera,
parallax, prolonged shutter allows blurring some
layers (motion blur)
25
Stop-motion Animation
  • Willis OBrien King Kong
  • Ray Harryhausen Mighty Joe Young
  • Nick Park Wallace and Grommit
  • Tim Burton Nightmare Before Christmas

26
Animation Heritage
  • 1963 Ivan Sutherlands (MIT) Sketchpad
  • 1970 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

27
Animation Heritage
  • 1970s New York Institute of Technology (NYIT)
    produced Alvy Ray Smith (Cofounded Pixar and
    Lucasfilm) and Catmull
  • 1980s Daniel and Nadia Magnenant-Thalmann
    (Swiss Universities) become European powerhouses

28
Animation Heritage
  • 1980s z-buffer invented, SGI founded, and
    Alias/Wavefront founded
  • 1977 Starwars
  • 1982 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)

29
Animation Heritage
  • 1986 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)

30
Animation Heritage
  • ILM 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 Egypt
  • Pixar Toy Story, A Bugs Life, Monsters Inc.

31
Americans are hardest working Recent history
  • United Nations report from Sept 1, 2003
  • /worker-year
  • US 60,728, Belgium (top EU) 54,333
  • hours/worker-year
  • US Japan 1825, EU 1300 1800
  • /worker-hour
  • Norway, France, Belgium, US 38 35
    34 32
  • Why is US on top of /worker-year?
  • Best economies encourage widespread use of
    communications and information technology
  • Even though were fat, dumb, and happy we dont
    take month-long vacations and one-year maternity
    breaks

32
Lets talk about computer animation
  • Must 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?

33
Animation A broad Brush
  • Traditional Methods
  • Cartoons, stop motion
  • Keyframing
  • Digital inbetweens
  • Motion Capture
  • What you record is what you get
  • Simulation
  • Animate what you can model (with equations)

34
Computer Animation
35
Keyframing
  • Traditional animation technique
  • Dependent on artist to generate key frames
  • Additional, inbetween frames are drawn
    automatically by computer

36
Keyframing
How are we going to interpolate?
From The computer in the visual arts, Spalter,
1999
37
Linear Interpolation
Simple, but discontinuous velocity
38
Nonlinear Interpolation
Smooth ball trajectory and continuous velocity,
but loss of timing
39
Easing
Adjust the timing of the inbetween frames. Can
be automated by adjusting the stepsize of
parameter, t.
40
Style or Accuracy?
  • Interpolating timecaptures accuracyof velocity
  • Squash and stretchreplaces motionblur stimuli
    andadds life-likeintent

41
Traditional Motivation
  • Ease-in andease-out is likesquash andstretch
  • Can weautomate theinbetweens forthese?

The Illusion of Life, Disney Animation Thomas
and Johnson
42
More squash and stretch
43
Anticipation and Staging
  • Dont surprise theaudience
  • Direct their attention to whatsimportant

44
Follow Through
  • Audience likes to see resolution of action
  • Discontinuities are unsettling

45
Combined
46
Secondary Motion
  • Characters should exist in a real environment
  • Extra movements should not detract

47
Interpolation
  • Many parameters can be interpolated to generate
    animation
  • Simple interpolation techniques can only generate
    simple inbetweens
  • More complicated inbetweening will require a more
    complicated model of animated object and
    simulation

48
Interpolation
  • Strengths
  • Animator has exacting control (Woodys face)
  • Weaknesses
  • Interpolation hooks must be simple and direct
  • Remember the problems with Euler angle interp?
  • Time consuming and skill intensive
  • Difficult to reuse and adjust

49
(No Transcript)
50
Examples
  • Sports video games
  • Madden Football
  • Many movie characters
  • Phantom Menace
  • Cartoons

51
Motion Capture Strengths
  • Exactly captures the motions of the actor
  • Michael Jordans video game character will
    capture his style
  • Easy to capture data

52
Motion Capture Weaknesses
  • Noise, noise, noise!
  • Magnetic system inteference
  • Visual system occlusions
  • Mechanical system mass
  • Tethered (wireless is available now)

53
Motion Capture Weaknesses
  • Aligning motion data with CG character
  • Limb lengths
  • Idealized perfect joints
  • Foot sliding
  • Reusing motion data
  • Difficult to scale in size (must also scale in
    time)
  • Changing one part of motion

54
Motion Capture Weaknesses
  • Blending segments
  • Motion clips are short (due to range and tethers)
  • Dynamic motion generation requires blending at
    run time
  • Difficult to manage smooth transition

55
(No Transcript)
56
Procedural
http//jet.ro/dismount
www.sodaplay.com
57
Examples
  • Inanimate video game objects
  • GT Racer cars
  • Soapbox about why this is so cool
  • Special effects
  • Explosions, water, secondary motion
  • Phantom Menace CG droids after they were cut in
    half

58
Procedural Animation
  • Very general term for a technique that puts more
    complex algorithms behind the scenes
  • Technique attempts to consolidate artistic
    efforts in algorithms and heuristics
  • Allows for optimization and physical simulation

59
Procedural Animation Strengths
  • Animation can be generated on the fly
  • Dynamic response to user
  • Write-once, use-often
  • Algorithms provide accuracy and exhaustive search
    that animators cannot

60
Procedural Animation Weaknesses
  • Were not great at boiling human skill down to
    algorithms
  • How do we move when juggling?
  • Difficult to generate
  • Expensive to compute
  • Difficult to force system to generate a
    particular solution
  • Bicycles will fall down

61
Fundamental Animation Techniques
62
Fundamental Animation Techniques
  • Squash and Stretch
  • Timing
  • Anticipation
  • Staging
  • Slow In and Slow Out
  • Arcs
  • Exaggeration
  • Secondary Action
  • Appeal
  • Personality

63
Squash and Stretch
64
More squash and stretch
65
Timing is everything!
66
Timing
  • Timing speed of action
  • Relays the idea behind the action
  • Too fast
  • might not notice at all
  • Might not understand whats happened
  • might not pay enough attention
  • Too slow
  • Sense of action can be lost
  • can become boring

67
Timing
  • Defines weight of the object
  • Heavy objects accelerate slowly
  • Size in general should correspond to the mass
  • Shows emotional state
  • Identical key frames can have different timing

68
Timing example
  • Two key frames
  • Head leaning toward the right shoulder
  • Head over left shoulder, chin slightly raised
  • Vary the number of in-between frames, 0 to 10
  • Very different ideas can be communicated

69
Timing example, cont.
  • 0 hit by tremendous force
  • 1 hit by a brick, frying pan
  • 2 nervous tick, muscle spasm
  • 3 dodging a brick, frying pan
  • 4 giving a crisp order Move it !
  • 5 friendly Over here. Come on - hurry
  • 6 sees a sports car he always wanted
  • 7 tries to get a better look at something.
  • 8 searches for a book on a shelf
  • 9 appraises, considering thoughtfully
  • 10 stretches a sore muscle
  • Example from Thomas and Johnson Disney
    animation the illusion of life

70
Anticipation
71
Anticipation
  • Action has three parts
  • Preparation for the action (anticipation)
  • Action itself
  • Termination of the action (follow through)
  • Need anticipation to
  • Make actions natural
  • Muscle movement (kicking a ball)
  • Prepare audience for the following action
  • Direct attention to another part of the screen

72
Anticipation
  • Slow action can use little anticipation
  • Meaning is carried by the action itself
  • Fast action need more anticipation
  • Need to know whats going to happen even before
    the action
  • Exaggerated anticipation
  • Emphasize extreme weight / action difficulty

73
Staging
74
Follow-Thru and Overlapping Action
75
Follow through
  • Actions rarely come to sudden stops
  • There are leading parts, other participating
    parts and appendages
  • Action starts by leading part
  • Main action follows
  • Appendages continue to move longer
  • Heavy ones drag along longer

76
Follow Through
  • Audience likes to see resolution of action
  • Discontinuities are unsettling

77
Overlapping action
  • Add variations to timing of loose parts
  • Little extra actions make it more interesting
  • New action starts BEFORE previous one stops
  • Full stops are rare
  • locking open door
  • Start walking to the door
  • Before coming to the door, reach for the door
  • Before completely closing, reach for the key, etc.

78
Slow in and slow out
  • Even spacing between frames constant speed
  • Better to have gradual acceleration and slowing
    down

79
Bouncing Ball Example
  • The 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.

80
Arcs
  • Visual path should be an arc
  • Rather than a straight line

81
Exaggeration and secondary action
  • Keep it balanced
  • Have some natural elements and some exaggerated
    ones
  • Secondary action results directly from primary
    action
  • Gives natural complexity
  • Can be missed if happens in the middle of major
    move
  • Should be obvious but kept secondary

The secondary action of Luxo Jr's forward motion
is the rippling of his power cord.
82
Exaggeration
83
Secondary Action
84
Appeal Personality
85
Basic Camera Shots
  • Wide Shot/Establishing Shot/Long Shot
  • Medium Shot
  • Close Up Shot
  • Cutaway Shot/Over the Shoulder
  • Two Shot/Three Shot
  • Sequence
  • Length of shot

86
Wide Shot/Establishing
87
Medium Shot
88
Close Up Shot
89
Extreme Close Up
90
Two Shot/Three Shot
91
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.
92
Basic Camera Moves
  • Zoom In
  • Zoom Out
  • Pan Right, Pan Left
  • Action in the frame.
  • Follow the action/rolling shot.

93
Standard Movie Openings
  • Movie Opening 1
  • Wide Shot
  • Zoom to Medium
  • Some Action.
  • Zoom to close-up
  • Out to Medium.
  • Most Bond Films
  • Movie Opening 2
  • Tight Close-Up
  • Out to Medium
  • Action
  • Zoom to close-up
  • Out to Medium
  • Run with it.
  • Raiders of Lost Ark
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