Animation
CS 551 / 651
Lecture 3
Classical Animation
Review
Keyframing
• Provides extensive user control
• Automated but difficult to capture artist effects
– Liner, nonlinear, easing, squash/stretch,
anticipation, follow-through, secondary motion
Review
Motion Capture
• Easy to capture style, but difficult to reuse/adapt
• Data cleanup / foot sliding
Review
Procedural
• Build once, use often
• Difficult to build
http://taat.fi/taat/porrasturvat/
www.sodaplay.com
Euler Angle Interpolation
Euler Angle (Roll, Pitch, Yaw)
• Frequently encoded as 3x3 matrix
• Simple interpolation fails:
Identity
Rotate 90 degrees Interpolated
about x axis
(not orthonormal)
0
0
1 0 0
1 0 0 1
0 1 0 interp
0 0 1  0 0.5 0.5
0.5







 

0 0 1
0  1 0 0  0.5 0 
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: 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
Readability of Actions
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
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
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?
Homework
Reader Hecker articles 1 and 2