1. Computer Animation Algorithms and Techniques
Behavioral Animation
Rick Parent
Computer Animation

2.
Rick Parent
Computer Animation

3. Behavioral Animation Individuals Groups Reactive behavior
Intelligent behavior
Personality
Groups
Aggregate behavior
Crowd behavior
Rick Parent
Computer Animation

4. Reactive Behavior If <condition> then <action>
current conditions - usually omniscence
simple action - carried out directly and immediately
problems of scale: conflicting rules
priority selection or ordering
Rick Parent
Computer Animation

5. Aggregate Behavior Type Elements Physics Intelligence
Typical qualities
Type
Elements
Physics
Intelligence
Particles
Much
None
Flocking
Some
Limited
Crowds
Little
Little-much
Rick Parent
Computer Animation

6. Primitive Behavior - Flocking
Local control – for realism, the flock member only reacts to locally accessible information
Perception – fov vision – angle can change with speed
Interacting with other members – stay with friends, avoid bumping into each other
Interacting with the environment – collision avoidance is primary
Rick Parent
Computer Animation

7. Primitive Behavior - Flocking
Original work by Craig Reynolds
Global control – need control of flock
script flock leader
global migratory urge
Negotiating the motion
Collision avoidance – steer to avoid
Splitting and rejoining – difficult to tune parameters
Modeling flight – e.g., banking into turns
Rick Parent
Computer Animation

8. Negotiating the Motion
Forces Or
“Reasoning”
(e.g. rule-based)
Rick Parent
Computer Animation

9. Navigating Obstacles:
Using repulsive forces
Rick Parent
Computer Animation

10. Navigating using bounding sphere
Rick Parent
Computer Animation

11. Testing for being on a collision path with (bounding) sphere
Navigating
Testing for being on a collision path with (bounding) sphere
Given: P, V, C, r
Rick Parent
Computer Animation

12. Finding closest non-colliding point
Rick Parent
Computer Animation

13. Navigating – finding a pass
Render in z-buffer
Sample environments with rays
Rick Parent
Computer Animation

14. Modeling Flight –common in flocking
Rick Parent
Computer Animation

15. Modeling Flight
Rick Parent
Computer Animation

16. Modeling Flight
Rick Parent
Computer Animation

17. Modeling Flight
Rick Parent
Computer Animation

18. Primitive Behavior - Prey-Preditor
unbalanced abilities
maximum velocity
maximum acceleration
maximum angular acceleration
maximum angular velocity
vision - distance, movement, fov
Rick Parent
Computer Animation

19. Knowledge about environment
Intelligent behavior
Reasoning
Causation
Knowledge about environment
Vision - immediately sensed
Memory - previous experience
Rick Parent
Computer Animation

20. Vision Omniscience – access to the database
FOV vision – culling but no occlusions
Occluded vision
ray casting – sample environment
z-buffer using object IDs as z’s
Object recognition - ?
Rick Parent
Computer Animation

21. Memory What is recorded about the environment Spatial occupancy
Transient events: time-stamps
Rick Parent
Computer Animation

22. Intelligent Behavior Autonomous behavior ‘Self-animated’ characters
Perception & reasoning about environment
Personality, emotions, dispositions
Manifestations of Individuality
Body Expressions and Gestures
Facial expressions
Speech
Rick Parent
Computer Animation

23. Internal State Models what the agent needs to do
Suggested precedence classes of internal state variables
Imperatives
Desires
Suggestions
Rick Parent
Computer Animation

24. Levels of Behavior Arbitration among competing intentions
Hooks for the animator to impose control
Rick Parent
Computer Animation

25. Expressions and Gestures
ToBI – Tones and Break Indices
LMA – Laban Movement Analysis
BEAT
EMOTE
RUTH
Greta
Rick Parent
Computer Animation

26. Modeling Individuality
Personality – long term qualities
Emotions – short term
Mood – third level?
Basic emotions?: happy, sad, fear, disgust, surprise, anger
Models of personality from psychology
OCEAN: openness, conscientiousness, extroversion, agreeableness, neuroticism
PEN: extraversion, neuroticism, psychoticism
OCC: how perceptions dictate emotional experience
Rick Parent
Computer Animation

27. Modeling Individuality
Improv
AlphaWolf
Rick Parent
Computer Animation

28. Crowd Management Emergent behavior
Statistical behavior v. believable individual behaviors
Homogeneous activity v. Internal structure
For evaluation
Pedestrian traffic simulation
Traffic flow
Emergency response modeling
For entertainment
Background crowds
Rick Parent
Computer Animation

29. Crowds Emergent behavior: similar to flocking collision avoidance
‘intelligent’ paths
Crowds
From a distance: statistical behavior
nonsensical detailed motion
reasonable visual effect
Internal structure
limited interaction among members
group formation
Rick Parent
Computer Animation