Hierarchical Model for Real Time Simulation of Virtual HumanCrowds

Bart van Greevenbroek

Overview

Article Authors ViCrowd Experiments Assessment

The Authors

Soraia Raupp Musse

Daniel Thalmann

The Article

Published in 2001 Cited 229 times Cited by “Finding Paths for Coherent

Groups Using clearance” (no 6 on our list) by Arno kamphuis and Mark Overmars

Controlling a Crowd

Scripted behaviors Reactive behaviors User-guided behaviors

Hierarchy

Crowds

Groups

Agents

ViCrowd

Behavioral based multi-level framework

Used to simulate crowds in real time Script-based language.

Knowledge, Beliefs and Intentions

Knowledge (information about the world)

Beliefs (states of emotion) Intentions (goals)

Events

Can change the knowledge, beliefs or intentions of an agent

And thus the behavior Example: A door closes, the

knowledge that the door closes changes, agents will not go through that door.

Example: A bomb goes off, agents within a radius panic, and behavior is altered.

Main Problems

Modeling of crowd information, also concerning the distribution of groups

Different levels of realism Required Structure to provide

interaction between groups of agents in real time

Related work

Different Types of Crowd Control

Priority

High level

Flocking Following Goal Changing Attraction Repulsion Split Space adaptability Safe-Wandering

Flocking

the agents from the same group share the same list of goals;

They walk at similar speeds; They follow the paths generated as

showed One agent can wait for another on

arrival at a goal when another agent from the same group is missing.

Following

A group can follow another group by sharing the same goals, either temporary or permanently.

Goal Changing

Agents can change groups, and this is influenced by the relationship value with each agent in the group (value between 0 and 1)

Agents have a leadership ability value, which is also taken into account

If an agent has a higher relationship with another group, it will join that group. If the leadership value is high enough

Attraction

The user can paint regions where the groups must be at a certain point, and the orientation can be influenced as well.

Groups are normally attracted to attraction points

Repulsion

Groups are repulsed by obstacles and each other (similar to the social force model)

Split

Groups can split randomly

Space Adaptability

The group wants to occupy all the walking space, using a bezier curve:

Safe-Wandering

Using a procedural method, the agents predict collisions using collision detection between two lines

Results (1)

Scripted Behavior (SB) Reactive Behavior (RB) Guided Behavior (GB)

Results (2)

Results (3)

Future work

Improving viCrowd script language by integrating Python

Panic and Emergency Behaviors

The Good

High level of compatibility with other methods

Very flexible system User has control over groups if

needed Groups are essential for a realistic

crowd, so its good to focus on groups Knowledge, Beliefs and Intentions is

a well-known paradigm in the AI field

The Bad

Performance is not awe-inspiring Exact formulae are missing No system specs are given, which

makes comparison with other methods difficult

A collection of simple motions are possible, but what about complex motions?

Seeing as groups follow attraction points, Oscillations can occur.

The ugly

The site with examples they mentioned, does not work.

Figures are sloppy, some text is cut off.

Meaningless pictures. If something is happening in the experiment involving motions, draw arrows or make the motion obvious.

In general, they go all over the place.