CS 551/651
Advanced Graphics
Introduction to Animation
Technical Background
Principles of Computer
Animation
• John Lasseter, "Principles of Traditional
Animation Applied to 3D Computer
Animation", Computer Graphics, pp.
35-44, 21:4, July 1987 (SIGGRAPH 87).
• Ollie Johnston and John Lasseter,
Course 1 at SIGGRAPH 94, "Animation
Tricks".
Comments from Lasseter
Keyframing
• Computers are stupid
– Worst case, keyframe require for every frame
• John discovered that some degrees of freedom
(DOFs) require more keyframes than others to
look natural
• You must start with a clear idea of the motion
you desire
• Plan actions with thumbnail sketches and plot
timing on exposure sheet
• Refer to sketches/timing frequently
Lasseter: 2-D vs. 3-D
• Native computer character is 3-D
– Sometimes makes it harder
• A character’s hand may go through its body
when seen from a certain angle
– Sometimes makes it easier
• Animation reuse: An animation may look very
different when seen from different locations
Lasseter: Weight and Size
• Rendering can make realistic-looking
objects (marble, feathers, steel)
• Good rendering benefits are lost if
animation is poor
• Physics matters – heavy things take
longer to start/stop moving…
• Proper timing/spacing of poses is more
important than the poses themselves
Lasseter: Weight and Size
• See videos on desktop
Lasseter: Thinking Character
• Every motion must exist for a reason
– Mood
– Personality
– Attitude
• You must convey the character’s
thoughts to tell the story
– Use anticipation
Lasseter: Anticipation
• Lead with the eyes
– Move eyes first, with lock-in of focus a few
frames before the head
– Head follows and leads the body by a few
frames
– More delay implies more thought required
• Use this relationship as a tool
– External forces cause opposite timing
relationship
Lasseter: Moving Holds
• Traditional 2-D animation permits “holds”
– Reuse of one drawing for multiple frames
– This is one way to control timing
• In computer animation action dies
immediately
– Perhaps due to realistic rendering and
smooth animations
• Eye picks it up every time
Lasseter: Moving Holds
• Have some part of the character continue to
move in same direction during holds
• Remember to coordinate realism of character
to realism of motions
– More realistic characters (rendering style and
dimensions) require more realistic movements
– This rule limits the straightforward reuse of human
facial mocap for non-human 3D characters
Lasseter: Emotion
• Character’s personality conveyed through emotion
• Emotion dictates animation pace
• Distinguish emotional state of two characters
through contrast in movement
– No two characters perform same action in same manner
Lasseter: Readability of Actions
• To make sure an idea or action is
unmistakably clear, the audience’s eye
must be led to the right place at the right
time
– Timing
• Not too slow or audience eyes wander
• Not too fast or action is misunderstood
• The faster the motion, the more critical it is to
make the audience focus on it
Harold Whitaker and John Halas, Timing for Animation, 1981
Lasseter: Readability of Actions
• To make sure an idea or action is
unmistakably clear, the audience’s eye
must be led to the right place at the right
time
– Staging
• Audience can only see one idea at a time
• Object of interest must be contrasted
against rest of scene
–Pick strongest and simplest technique
–Ex: Still object vs. busy background
Lasseter: Readability of Actions
• To make sure an idea or action is
unmistakably clear, the audience’s eye
must be led to the right place at the right
time
– Anticipation
• First action should not be brought to
complete stop before starting second
• Slight overlapping preserves flow
• Ex: Luxo Jr.
Lasseter: Story Tricks
• Animation must be timed to stay slightly
ahead or behind audience’s understanding
– Ahead conveys suspense and surprise
• Initial scene of Luxo Jr. where Dad is surprised by
ball
• Closing scene of Red’s Dream
– Behind reveals the story to the audience
before a character to convey character’s
discovery
Lasseter: Ask Why
• Why is this here?
• Does it further the story?
• Does it support the whole?
– Change of shape shows a character is thinking
– “It is the thinking that gives the illusion of life.
It is the life that gives meaning to the expression”1
– “It’s not the eyes, but the glance – not the lips, but
the smile”2
1.
Frank Thomas and Ollie Johnston, Disney Animation – The Illusion of Life, 1981
2.
Saint-Exupery, Wind, Sand, and Stars, 1932
Johnston Notes
• Use attitudes and actions to illustrate
ideas and thoughts, not words and
mechanical movements
• Squash and stretch the entire body for
attitudes
– Preserve volume
– Useful for face too
Johnston Notes
• Change of expression and dialog are
points of interest – don’t move head too
much
• Concentrate on drawing clear, not clean
• Everything has a function – know why
• Let the body attitude echo the facial
• Find best part of character’s pose to
squash and stretch
Johnston Notes
• The eye is pulled by the eyebrow muscles
• Get a plastic quality in the face
– Cheeks, mouth, and eyes
• The audience has a difficult time reading the
first 6 – 8 frames
• Actions can be eliminated and staging
“cheated” if it simplifies the picture you are
trying to show and it doesn’t disturb the
audience
Johnston Notes
• Spend half your time planning your
scene and the other half animating
• How to animate a four-legged walk:
– Work out acting patterns with squash and
stretch in body, neck, and head
– Animate the legs
– Adjust up and down motion of body
according to legs
Anticipation
• Can be anatomical
– Swinging your foot back before kicking
• Device that attracts viewer’s attention
– Staring off camera until character enters at
that position
• Can help convey mass. More wind-up
or concentration implies increased scale
Staging
• Contrast is powerful staging technique
– Motion is one example
– Original Disney characters were black and
white (no grayscale)
• Important motions had to be drawn in silhouette
because limbs passing in front of others were
not easy to see
• Even when grayscale (and color) is possible,
silhouette makes actions more visible
Follow through and
Overlapping Action
• "It is not necessary for an animator to take a
character to one point, complete that action
completely, and then turn to the following
action as if he had never given it a thought
until after completing the first action. When a
character knows what he is going to do he
doesn't have to stop before each individual
action and think to do it. He has it planned in
advance in his mind."
Walt Disney
Ease-in and Ease-out
• A facsimile of physics
– First, second, and third order continuity
– Remember challenges getting splines to
interpolate endpoints
Production Line
• Film a Sequences a Shot/Scene a Frames
• Preliminary story a Script a Storyboard
• Model Sheet
– Multiple drawings for each character
• Exposure Sheet
– Sound track cues, camera moves, and compositing
info for each frame
• Route Sheet
– Personnel responsible for each scene
Production Line
• Animatic or Story reel
– First pass at motion
• Scratch track
– First pass at audio (music, special fx, dialog)
Who Does What
• Story Department: build the storyboard
• Art Department: build consistent look to
coloring, lighting, models
• Modeling Department: build character
and prop models. Give character’s
hooks that animators can use to move
• Layout Department: build 3-D world for
staging and blocking
Who Does What
• Shading Department: builds texture
maps, shaders, lighting models
• Animation Department: animate
• Lighting Department: position lights
(hundreds) and camera to create final
image
• Camera Department: I want to be a
cowboy… render wrangling
Editing
• Nonlinear editing
– Cut and paste frames anywhere in animation
• Film splicing
• Video tape copying
– Source aDestination (Assemble Editing)
– Character generator and special effects
– Cannot splice into middle of destination reel (linear
editing)
– Industry standard: Sony BetaSP
• Frame accurate inserts
• Low quality degredation
Analog Editing
• Nothing is consistent
– Two decks play at different speeds (time-based
corrector / blackburst generator)
– NTSC refresh signal helps to synchronize
– Society of Motion Picture and Television Engineers
(SMPTE) time code is absolute 8-digit tag that is
pre-striped onto the tape (the parts of the visual
image TVs don’t show)
• Underscanning reveals
– Insert Editing allows flexible selection of insert
points on destination tape
Digital Editing
• Frames are always represented digitally
(no degeneration)
• Infinite compositing
• 21Mb/sec required for playback
• 1 hour of video = 76 Gb of storage
• D1 and digital Betacam are industry
standard
• Digital to analog or film?
Animation Heritage
• 1963 – Ivan Sutherland’s (MIT) Sketchpad
• 1970 – Evans and Sutherland (Utah) start
computer graphics program (and Co.)
• 1972 – Ed Catmull’s (Utah) animated hand
and face (later co-founded Pixar)
• 1970’s – Norm Badler (Penn) Center for
Modeling and Simulation
and Jack
Animation Heritage
• 1970’s – New York Institute of
Technology (NYIT) produced Alvy Ray
Smith (Cofounded Pixar and Lucasfilm)
and Catmull
• 1980’s – Daniel and Nadia MagnenantThalmann (Swiss Universities) become
European powerhouses
Animation Heritage
• 1980’s – 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)
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)
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 Bug’s Life, Monster’s Inc.
Homework
• Download FLTK 1.1 (pronounced Fulltick)
– www.fltk.org
• Compile visualc directory
• Get cube rendering program working
• We’re going to use fltk to build user
interfaces for our OpenGL/glut programs