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

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

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ARTIS-GRAVIR / IMAG INRIA ICA INPG 3D visualization NPR style –Coherent with the style of the scene –Historical references for the costumes Real-time rendering –Each character is a billboard –We texture it with a movie of a walking person: 20 points of view and 8 different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