using the corridor map method for path planning for a large number of characters roland geraerts,...
TRANSCRIPT
Using the Corridor Map Method for Path Planning for a Large Number of Characters
Roland Geraerts, Arno Kamphuis, Ioannis Karamouzas, Mark OvermarsMIG’08
Do We Need a New Path Planning Algorithm?
Robotics Virtual environments
Nr. Entities a few robots many characters
Nr. DOFs many DOFs a few DOFs
CPU time much time available little time available
Type path nice path natural path
Algorithms A*, roadmap-based, waypoint-based, …
A*, roadmap-based, waypoint-based, …
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
• …
Outline
• Corridor Map Method• Path variation• Obstacle avoidance• Crowd simulation• Coherent groups• Conclusions & future work
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
The Corridor Map Method
• Construction phase (off-line)
McKenna MOUT environment Footprint and Corridor Map: 0.05s
The Corridor Map Method
• Construction phase (off-line)
City environment Footprint and Corridor Map: 0.64s
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
The Corridor Map Method
• Query phase (on-line)
McKenna MOUT environment Corridor and path: 0.2ms (average)
The Corridor Map Method
• Query phase (on-line)
City environment Corridor and path: 1.2ms (average)
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
Obstacle Avoidance
• Helbing and Molnar’s 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
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
Crowd Simulation
• Goal oriented behavior• Forces: standard force, biasing force, collision avoidance force
Crowd Simulation
• Goal oriented behavior• Forces: standard force, biasing force, collision avoidance force
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
Coherent Groups
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
• …