simulating virtual human crowds with a leader-follower model tsai-yen li, ying-juin jeng, shih-i...
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Simulating Virtual Human Crowds with a Leader-Follower Model
Tsai-Yen Li, Ying-Juin Jeng, Shih-I ChangNational Chengchi University
Slides updated and presented by Vishal SrivastavaOriginal slides by Romain Thibaux, Benson Limketkai
Problem Goal is to simulate the behavior of
crowds of people A crowd must navigate an
environment with: Obstacles Other moving crowds
Incredibly high degrees of freedom
Potential applications Virtual shopping in a 3D shopping
mall
Distributed networked games
Simulation of a tour group
Crowds Crowds contain one “leader” and
many “followers” Given a goal, the leader is in charge
of planning motions for its group Followers follow the leader closely as
it moves toward its goal
General Approach Decoupled planning approach
Paths executed by other leaders become the motion constraint for the current leader
Path planner estimates the shape and space of each group
Motion for followers is determined by artificial steering forces
Planning for Two Leaders
1
2
1
2
1
2
Path is planned using artificial potential field
Planning for Two Leaders
1
2
Coordinated motions
Solid circles mark leader positions
Circle traces are planned paths
Numbers indicate planning order
Four snapshots…
Motion of the Followers
Separation
Cohesion
Alignment
Obstacles
Leader
Steering Forces
Local Minima
Solution: Modify the attractive force to the leader’s last seen location.
Model the shape of crowds Treat each crowd as an object with
variable shape Estimate the shape Extend in CT-space when planning
Motion Planning For Crowds
Crowd Region Estimation Leader’s path
forms an axis Draw a half-circle
with diameter D behind the leader
Sweep the half-circle backward along the axis until it can accommodate all the followers
Example of Crowd Region Estimation
Implementations and Experiments
Stand-alone simulation module in Java
128 x 128 grid “planning time … is usually
fractions of a second” “planning times … are 500ms and
2000ms … on a low-end PC”
Screen shots
Concerns Is motion really human-like?
Is planning too expensive for real applications?
Summary
A planning system for generating coordinated motion for multiple crowds
Planner features: Crowd shape estimation module Integrated view of crowd motion planning
Applications in shared virtual environments and computer animation