Transcript Simulating Crowds

Simulating Crowds
Simulating Dynamical Features of Escape Panic &
Self-Organization Phenomena in Pedestrian Crowds
Papers by Helbing
Presented by Thiago Ize
Why do we care?
Easy to use when doing crowds
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For the layman animator
For the sleep deprived programmer
Lots of goodies come for free 
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Escape panic features
Faster-is-slower effect
Crowding around doorway
Mass behavior
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Normal pedestrian traffic features
Lanes
Waiting at doors
Braking rules
The model
Missing the
 !
B
gets α to desired
0
velocity, v e
closest part of static
things, Β, that α
should avoid
pushes α away
from all
pedestrians, β
pushes α towards
certain pedestrians, i

B
These use potential force fields
What are potential force fields?
Field around an object that exerts a force
on other objects
Used by roboticists
exponential
square
directional
The model – normal condition
Lots of room for choice of potential function
Helbing uses an elliptical directional potential
directional
Directional potential:
Gradient:
α
Force applied on α by β:
β
α
α
What does that do?
Lane formation
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Potential force behind leader is low
Leader is moving away (force is not
increasing)
Turn taking at doorways (it’s a polite model)
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Easy to follow someone through the door.
Eventually pressure from other side builds up
and direction changes
Rudimentary collision avoidance
Panic !!
People are now really close together
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Body force – counteracts bodily compression
Sliding friction force – people slow down when
really close to other people and things
Desired speed, v0 , has increased
Switch from directional to exponential
potential field (but would probably still work with directional)
The model - panic condition
Exponential
potential field
body force
sliding friction force
r  d
t
 ( Ai e
 kg(r  d )) n  g (r  d )v
t
Bi
g() = 0 if α and β
are not touching,
otherwise = r  d
distance from α to β
r  radius   radius 
d  r  r
normal from β to α
n 
r  r
d ij
tangential velocity
difference
t
v
 (v  v )  t
What does that do?
Faster-is-slower effect
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Sliding friction term
High desired velocity (panic)
Squishes people together
Gaps quickly fill up
Exits get an arch-like blockage
Integrating panic with normality
Sliding friction and body term can safely
be used in all situations
Would probably make all scenes look
better
Panic occurs when everyone’s desired
velocity is high and points to same location
Mass behavior
Confused people will follow everyone else
individual direction
panic probability
average direction of
neighbors j in a
certain radius Ri
Problems
Possible to go through boundaries
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Can be fixed by increasing force of boundary
Sometimes good
Excels at crowds, not individual pedestrian
movement
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When focus is on big crowds and not on
individuals, this is good.
Questions?