Computer Animation
Computer Graphics
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Computer Animation
• What is Animation?
• Make objects change over time
according to scripted actions
• What is Simulation?
• Predict how objects change over time
according to physical laws
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3 Types of Animation
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Historically there are 3 major types of animation:
1. Hand Drawn Animation
2. Stop Motion Animation
3. Computer Animation
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Hand Drawn Animation
• Done by an artist who draws each character and
movement individually
• Very time consuming to have to draw, then colour, then
photograph each picture
• Draw pictures first, then colour them on celluloid, then
they take pictures and animate them
• Very expensive due to hours of labour involved
• Examples: Older Disney Movies i.e. Bambi, Fox and
Hound, Cinderella etc.
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Hand Drawn Animation
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Stop Motion Animation
• Can be done by virtually anyone, with no extensive
training
• Does not take that much time relative to the other 2
methods
• Uses jointed figures or clay figures that can be moved
to make motions
• Take still pictures of the individual movements, then
use relatively inexpensive computer software to
animate
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Stop or Model Animation
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Animation uses
• Animated Movies: Million dollar industry;
• 1- 20 millions spent on each movie
• Animation & Computer Graphics Effects are
used in movies frequently
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Outline
• Principles of Animation
• Keyframe Animation
• Articulated Figures
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Principle of Traditional Animation
– Disney –
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Squash and Stretch
Slow In and Out
Anticipation
Exaggeration
Follow Through and Overlapping Action
Timing
Staging
Straight Ahead Action and Pose-to-Pose Action
Arcs
Secondary Action
Appeal
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Squash and Stretch
Stretch
Squash
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Squash and Stretch
• The most important principle is "squash and
stretch", the purpose of which is to give a sense of
weight and flexibility to drawn objects. It can be
applied to simple objects, like a bouncing ball, or
more complex constructions, like the muscles of a
human face.
• A figure stretched or squashed to an exaggerated
degree can have a comical effect.
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Squash and Stretch
• In realistic animation, however, the most
important aspect of this principle is the fact that an
object's volume does not change when squashed or
stretched. If the length of a ball is stretched
vertically, its width (in three dimensions, also its
depth) needs to contract correspondingly
horizontally.
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Slow In and Out
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Slow in and Slow out
• The movement of the human body, and most other
objects, needs time to accelerate and slow down.
For this reason, animation looks more realistic if it
has more drawings near the beginning and end of
an action, emphasizing the extreme poses, and
fewer in the middle.
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Slow in and slow out
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Anticipation
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Anticipation
• Anticipation is used to prepare the audience for an
action, and to make the action appear more
realistic. A dancer jumping off the floor has to bend
his knees first; a golfer making a swing has to swing
the club back first.
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Exaggeration
• Exaggeration is an effect especially useful for
animation, as perfect imitation of reality can look
static and dull in cartoons. The classical definition
of exaggeration, employed by Disney, was to
remain true to reality, just presenting it in a wilder,
more extreme form. Other forms of exaggeration
can involve the supernatural, alterations in the
physical features of a character, or elements in the
storyline itself.
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Exaggeration
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Follow through and overlapping
actions
• . "Follow through" means that loosely tied parts of
a body should continue moving after the character
has stopped and the parts should keep moving
beyond the point where the character stopped to
be "pulled back" only subsequently towards
the center of mass.
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Timing and Motion
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Gives meaning to movement.
Proper timing is critical to making ideas
readable.
Examples:
1. Timing: tiny characters move quicker than
larger ones.
2. Motion: can define weights of objects.
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4. Staging
A clear presentation of an idea.
Some Techniques:
1. Use motion in a still
scene or use of static
movement in a busy
scene.
2. Use of silhouettes (to
the side)
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Straight Ahead Action and Poseto-Pose Action
1. Straight Ahead
Animator start from first drawing in the scene and
draw all subsequent frames until the end of scene.
2. Pose-to-Pose
Animator plans actions, draws a sequence of poses, in
between frames etc.
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Arcs
• Visual path of action for natural movement.
• Makes animation much smoother and less stiff
than a straight line.
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Secondary Action
• Action that results directly from another action.
• Used to increase the complexity and interest of a
scene.
Example:
Body movement is the
primary action, facial
expression is the
secondary action
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Appeal
• Refers to what an audience would like to see.
• Character cannot be too simple (boring) or too
complex.
Examples:
Avoid mirror symmetry,
assymmetry is interesting.
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Role of Personality
• Animator’s first goal is to entertain.
• Success of animation lies in the personality of the
characters.
Conclusion
Hardware/Software are simply not enough, these
principles are just as important tools too.
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That’s All Folks!
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Outline
• Principles of Animation
• Keyframe Animation
• Articulated Figures
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Keyframe Animation
• Define Character Poses at Specific Time Steps
Called “Keyframes”
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Keyframe Animation
• Interpolate Variables Describing Keyframes to
Determine Poses for Character in between
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Inbetweening
• Linear Interpolation
• Usually not enough continuity
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Inbetweening
• Spline Interpolation
• Maybe good enough
• May not follow physical laws
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Outline
• Principles of Animation
• Keyframe Animation
• Articulated Figures
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Articulated Figures
• Character Poses Described by Set of Rigid Bodies
Connected by “Joints”
Base
Arm
Hand
Scene Graph
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Articulated Figures
• Well-Suited for Humanoid Characters
R
R
R
R
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Articulated Figures
• Joints Provide Handles for Moving Articulated
Figure
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Example: Walk Cycle
• Articulated Figure:
Hip
Upper Leg
Knee
Lower Leg
Ankle
Foot
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Example: Walk Cycle
• Hip Joint Orientation:
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Summary
• Animation Requires ...
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Modeling
Scripting
Inbetweening
Lighting, shading
Rendering
Image processing
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