ARTIS-GRAVIR / IMAG INRIA

ICA INPG

A Physically-Based Particle Model of Emergent Crowd

Behaviors

Laure Heïgeas, Annie Luciani,

Joelle Thollot, Nicolas Castagné

ICA INPG

ARTIS-GRAVIR/IMAG INRIA

ARTIS-GRAVIR / IMAG INRIA

ICA INPG

The agora of Argos•Center of the social life

•A visitor should have a feeling of this

•We need to put people walking around during our walkthrough session

•CG research question : how to animate a crowd and to render it in real time ?

ARTIS-GRAVIR / IMAG INRIA

ICA INPG

What kind of crowd

•We focus on collective behavior

•One character has to avoid others and buildings

•We try to produce some emergent behaviors: flows, files, groups

•We need a generative model

ARTIS-GRAVIR / IMAG INRIA

ICA INPG

State of the art•Three main approaches:

– Kinematic: key frames and interpolations preset the animation

– Agent systems: agents are managed in real time by rules of behavior defined with automata

– Particle-based system: particles are animated in real time by the application of different forces

•Particle systems seem to be well adapted: generative and simple, no need for special rules

ARTIS-GRAVIR / IMAG INRIA

ICA INPG

Our methodology•Analysis of the dynamic of a crowd:

– Dynamic structures• Traffic jams

• Flows

• Queues

– Obstacle avoidance• Distance around obstacles: apparent volume

• Distance around people: psychophysical volume

ARTIS-GRAVIR / IMAG INRIA

ICA INPG

Our methodology• Synthesis of the dynamic effects

– One character = one particle on a 2D ground

– Building = several particules

– Elastic interaction, piecewise linear• Thresholds given by the analysis

C - Impenetrable zone

B - Avoidance zone

A - Long DistanceAnticipation zone

F

D

D1 D2 D3

ARTIS-GRAVIR / IMAG INRIA

ICA INPG

Results•2D visualization of the trajectories

 

Avoidance of two persons passing face to face

The red discs form a queue and the green ones jam together

ARTIS-GRAVIR / IMAG INRIA

ICA INPG

3D visualization•NPR style

– Coherent with the style of the scene– Historical references for the costumes

•Real-time rendering– Each character is a billboard– We texture it with a movie of a walking person:

20 points of view and 8 different characters

[ Loscos et al. 02]

ARTIS-GRAVIR / IMAG INRIA

ICA INPG

Conclusion•Results:

– Reproduction of complex dynamic behaviors– Simple interaction model between pairs of objects– 3D real-time visualization

•Future works– Allowing the user to interact with the crowd real-time simulation– Anisotropic model of a character: front/back