  This paper presents a modeling process in order to produce a realistic
simulation of crowds in the ancient Greek agora of Argos. This place was a
social theater in which two kinds of collective phenomena took place:
interpersonal interactions (small group discussion and negotiation, etc.) and
global collective phenomena, such as flowing and jamming. In this paper, we
focus on the second type of collective human phenomena, called non-deliberative
emergent crowd phenomena. This is a typical case of collective emergent
self-organization. When a great number of individuals move within a confined
environment and under a common fate, collective structures appear
spontaneously: jamming with inner collapses, organized flowing with queues,
curls, and vortices, propagation effects, etc. These are particularly relevant
features to enhance the realism - more precisely the "truthfulness" - of models
of this kind of collective phenomena. We assume that this truthfulness is
strongly associated with the concept of emergence: evolutions are not
predetermined by the individual characters, but emerge from the interaction of
numerous characters. The evolutions are not repetitive, and evolve on the basis
of small changes. This paper demonstrates that the physically-based interacting
particles system is an adequate candidate to model emergent crowd effects: it
associates a large number of elementary dynamic actors via elementary
non-linear dynamic interactions. Our model of the scene is regulated as a
large, dynamically coupled network of second order differential automata. We
take advantage of symbolic non-photorealistic and efficient visualization to
render the style of the person, rather than the person itself. As an artistic
representation, NPR reinforces the symbolic acceptance of the scene by the
observer, triggering an immediate and intuitive recognition of the scene as a
plausible scene from ancient Greece.
