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Journal Articles Computers and Graphics Year : 2021

SPH crowds: Agent-based crowd simulation up to extreme densities using fluid dynamics

Abstract

In highly dense crowds of humans, collisions between people occur often. It is common to simulate such a crowd as one fluid-like entity (macroscopic), and not as a set of individuals (microscopic, agent-based). Agent-based simulations are preferred for lower densities because they preserve the properties of individual people. However, their collision handling is too simplistic for extreme-density crowds. Therefore, neither paradigm is ideal for all possible densities. In this paper, we combine agent-based crowd simulation with Smoothed Particle Hydrodynamics (SPH), a particle-based method that is popular for fluid simulation. We integrate SPH into the crowd simulation loop by treating each agent as a fluid particle. The forces of SPH (for pressure and viscosity) then augment the usual navigation behavior and contact forces per agent. We extend the standard SPH model with a dynamic rest density per particle, which intuitively controls the crowd density that an agent is willing to accept. We also present a simple way to let agents blend between individual navigation and fluid-like interactions depending on the SPH density. Experiments show that SPH improves agent-based simulation in several ways: better stability at high densities, more intuitive control over the crowd density, and easier replication of wave-propagation effects. Also, density-based blending between collision avoidance and SPH improves the simulation of mixed-density scenarios. Our implementation can simulate tens of thousands of agents in real-time. As such, this work successfully prepares the agent-based paradigm for crowd simulation at all densities.
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Dates and versions

hal-03270915 , version 1 (25-06-2021)

Identifiers

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Wouter van Toll, Thomas Chatagnon, Cédric Braga, Barbara Solenthaler, Julien Pettré. SPH crowds: Agent-based crowd simulation up to extreme densities using fluid dynamics. Computers and Graphics, 2021, 98, pp.306-321. ⟨10.1016/j.cag.2021.06.005⟩. ⟨hal-03270915⟩
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