Using the Corridor Map Method for Path Planning for a Large Number of Characters

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Using the Corridor Map Method for Path Planning
for a Large Number of Characters

• Roland Geraerts, Arno Kamphuis, Ioannis
  Karamouzas, Mark Overmars
• MIG08

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Do We Need a New Path Planning Algorithm?
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Goals

• Fast and flexible path planner
• Real-time planning for thousands of characters
• Dealing with local hazards
• Natural paths
• Smooth
• Short
• Keeps some distance to obstacles
• Avoids other characters

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Outline

• Corridor Map Method
• Path variation
• Obstacle avoidance
• Crowd simulation
• Coherent groups
• Conclusions future work

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The Corridor Map Method

• Construction phase (off-line)
• Create a system of collision-free corridors for
  the static obstacles
• Extract the Generalized Voronoi Diagram
• If a path exists, then it can be found
• All cycles are included
• Corridors have maximum clearance

Sampled GVD
Corridor Map GVD clearance info
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The Corridor Map Method

• Construction phase (off-line)

McKenna MOUT environment
Footprint and Corridor Map 0.05s
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The Corridor Map Method

• Construction phase (off-line)

City environment
Footprint and Corridor Map 0.64s
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The Corridor Map Method

• Query phase (on-line)
• Extract corridor for given start and goal ?
  provides global route
• The characters follows an attraction point ?
  provides local route
• Runs along backbone path toward goal
• Used to define a force function, applied to the
  character
• Path is obtained by integration over time while
  updating the velocity, position, and attraction
  point of the character
• Yields a smooth (C1-continuous) path
• Other behavior locally adjust path by adding
  forces

Query points
Corridor andbackbone path
Path
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The Corridor Map Method

• Query phase (on-line)

McKenna MOUT environment
Corridor and path 0.2ms (average)
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The Corridor Map Method

• Query phase (on-line)

City environment
Corridor and path 1.2ms (average)
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Path Variation

• Alternative paths for a character
• Provides a less predictable opponent (in a game)
• May enhance the realism of the gaming experience
• Approach
• Add a random force (bias) to the character
• Control the direction of the bias by e.g. Perlin
  Noise

100 random paths
Lane formation
Shorter path
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Obstacle Avoidance

• Helbing and Molnars social force model forces
• Acceleration toward the desired velocity of
  motion
• Repulsive forces from other characters and
  borders to keep some clearance
• Attractive forces among characters
• We need efficient nearest neighbor computations
• 2D grid storing the characters

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Crowd Simulation

• Goal oriented behavior
• Each character has its own long term goal
• A start and goal fixes a corridor
• When a character has reached its goal, a new goal
  will be chosen
• Wandering behavior
• Each character makes local decisions
• Each character follows its attraction point
• When the attraction point reaches a vertex in the
  corridor map, one of the outgoing edges is
  selected

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Crowd Simulation

• Goal oriented behavior
• Forces standard force, biasing force, collision
  avoidance force

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Crowd Simulation

• Goal oriented behavior
• Forces standard force, biasing force, collision
  avoidance force

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Coherent Groups

• In a coherent group, characters stay close to
  each other
• Group coherence is obtained by limiting
• The width of the corridor
• The extent along the corridor where the
  characters can move

Large width and area
Small width, large area
Small width and area
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Coherent Groups
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Conclusions

• The Corridor Map Method is fast
• 10,000 characters can be simulated in real-time
• The Corridor Map Method is flexible
• Path variation
• Collision avoidance
• Crowds
• Coherent groups
• The Corridor Map Method produces natural paths
• Smooth
• Short
• Keeps some distance to obstacles