Simulating Crowds Simulating Dynamical Features of Escape Panic

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Simulating Crowds Simulating Dynamical Features
of Escape Panic Self-Organization Phenomena
in Pedestrian Crowds

• Papers by Helbing
• Presented by Thiago Ize

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Why do we care?

• Easy to use when doing crowds
• For the layman animator
• For the sleep deprived programmer
• Lots of goodies come for free ?
• Escape panic features
• Faster-is-slower effect
• Crowding around doorway
• Mass behavior
• Normal pedestrian traffic features
• Lanes
• Waiting at doors
• Braking rules

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The model
Missing the !
pushes a away from all pedestrians, ß
closest part of static things, ?, that a should
avoid
gets a to desired velocity,
pushes a towards certain pedestrians, i
These use potential force fields
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What are potential force fields?

• Field around an object that exerts a force on
  other objects
• Used by roboticists

exponential
square
directional
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The model normal condition

• Lots of room for choice of potential function
• Helbing uses an elliptical directional potential

directional
Directional potential
Gradient
a
ß
a
a
Force applied on a by ß
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What does that do?

• Lane formation
• Potential force behind leader is low
• Leader is moving away (force is not increasing)
• Turn taking at doorways (its a polite model)
• Easy to follow someone through the door.
• Eventually pressure from other side builds up and
  direction changes
• Rudimentary collision avoidance

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Panic !!

• People are now really close together
• Body force counteracts bodily compression
• Sliding friction force people slow down when
  really close to other people and things
• Desired speed, , has increased
• Switch from directional to exponential potential
  field (but would probably still work with
  directional)

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The model - panic condition
Exponential potential field
body force
sliding friction force
g() 0 if a and ß are not touching, otherwise
distance from a to ß
tangential velocity difference
normal from ß to a
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What does that do?

• Faster-is-slower effect
• Sliding friction term
• High desired velocity (panic)
• Squishes people together
• Gaps quickly fill up
• Exits get an arch-like blockage

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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 everyones desired velocity is
  high and points to same location

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Mass behavior

• Confused people will follow everyone else

average direction of neighbors j in a certain
radius Ri
individual direction
panic probability
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Problems

• Possible to go through boundaries
• Can be fixed by increasing force of boundary
• Sometimes good
• Excels at crowds, not individual pedestrian
  movement
• When focus is on big crowds and not on
  individuals, this is good.

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Questions?