Artificial Fishes:
Physics,
Locomotion,
Perception,
Behavior
Mar. 30, 2001
Xiaoyuan Tu and Demetri Terzopoulos,
Dept. of CS, University of Toronto
Presentation by Siddharth Dalal
Intro & Background
• What do fish do?
– eat, survive, when compelled by their libidos….
• Physics based graphic modeling
• Worm Dynamics, facial model
– more sophisticated spring mass model
• advanced behavioral animation
Any fish is good if caught on the hook.
Overview
Intention focuses sensory data causing behavior
Fishics 1 - Mechanics
• Spring Mass Model
2
d x
dx
w
mi 2  qi
 wi  f i
dt
dt
m = mass
x = position
q = damping factor
w = net force due to springs
f = external force
Fishics 2 - Hydrodynamics
• Swimming - Muscles + Hydrodynamics
Fishics 3 - Motor Controllers
• Swim MC
• Left and right MC
• Anterior and Posterior of fish - r1, s1, r2, s2
• Max params scaled from 0 - 1 to produce
varying speeds
Sensory Perception
• Two on board environment sensors:
– Vision Sensor - extracts information from scene
geometry, object database, physical simulation.
Cyclopean(?) vision - 300o viewing angle.
– Temperature sensor - senses ambient temp. at
center of body
Behavio(u)r 1
• Intention based on
– Habits
– Mental State
– Incoming Sensory Information
• decides behavior routine
• incremental - needs memory
Behavior 2 - Habits and Mind
• Habits - does fish like brightness, schooling,
male or female (yes this is in habits)
• Mental State
–
–
–
–
Three mental states - HLF - hunger, libido, fear
H= min[1-n(t)R(Δt)/α, 1]
L=min[s(Δt)(1-H(t)), 1]
(Fish like sex after dinner )
F=min[Σf, 1], f=min[D/d(t), 1]
Intentions 1
• Intentions
–
–
–
–
–
–
–
avoid,
escape
school
eat
mate
leave
wander
Intentions 2
• Features of Generator
– Persistence in intentions - no dithering
– focusser - focus on most important intention
• Create ‘abnormal fish’
– warp intentions
Intentions 3
• Behavior routines:
– eight - avoid static obstacle, avoid fish, eat,
mate, leave, wander, escape, school
– chasing target subroutine
– other subroutines - looping?, circling,
ascending?, nuzzling
Fish Type = Warped Intentions
• Artificial Fish Types
– Predators
• don’t escape, mate or
school
• always cruise, so don’t
leave
Fish Type = Prey Fish Grey Fish
• Artificial Fish Types
– Prey
• school
• evade predators
Pacifists
• Artificial Fish Types
– Pacifist
• no school, no escape
• just mate
• complex mating behavior implemented…
–
–
–
–
fish i chooses partner j
criteria if i is female/male
looping, circling, chasing-target, nuzzling
etc.
Result
• 10 fish, 15 food particles,
5 static obstacles at 4fps
on SGI R4400 Indigo2
• Future:
– reproduction
– other work
Links
• http://www.dgp.toronto.edu/people/tu/tu.html
• http://citeseer.nj.nec.com/tu94artificial.html
• http://www.cs.toronto.edu/~dt/
Guests and fish start to stink after two days.