Absh-act -This paper describes a model for simulating crowds of humans in real time. We deal with a hierarchy composed of virtual crowds, groups and individuals. The groups are the most complex structure that can he controlled in different degrees of autonomy. This autonomy refers to the extent to which the virtual agents are independent of the user intervention and also the amount of information needed to simulate crowds. Thus, depending on the complexity of the simulation, simple behaviors can be sufficient to simulate crowds. Otherwise, more complicated behavioral rules can be necessary, and in this case, it can be included in the simulation data in order to improve the realism of the animation. We present three different ways for controlling crowd behaviors: i) by using innate and scripted behaviors; ii) by defining behavioral rules, using events and reactions, and, iii) by providing an extemal control to guide crowd behaviors in real time. The two main contributions of our approach are: the possibility of increasing the complexity of grouplagent behaviors according to the problem to be simulated, and the hierarchical structure based on groups to compose a crowd. Index Terms -crowd motion, degrees of autonomy, reactive behaviors, behavioral animation, synthetic autonomous agents, virtual human crowds. Individual behavior in its most elementary form can be difficult to model. As soon as we consider several individuals and the interrelationships between them, the complexity d the system is substantially increased. In addition, the mass behaviors and motion of a large number of people have been studied and modeled in computer with different purposes. Some examples of crowd applications are the simulation of a realistic motion of numerous virtual people, which can be directed, as easily as only one agent and the emergent crowd motion simulation providing the evacuation of people in complex environments. Yet, if the application is to he processed in real time, e.g. integrated in a CVE (Collaborative Virtual Environment) including interactive aspects, a reasonable frame rate is required. This paper presents ViCrowd, a behavioraLbased multi-level framework to simulate virtual human crowds in real time. At the end of this paper, the time processing for the different levels of control that are discussed in this paper, are presented. First of all, we present some useful concepts that have been assumed in this work. A virtual human agent (here after referred to as an agent) is a humanoid whose behaviors are inspired by those of humans' [16]. The term group is used to refer to a group of agents whereas crowd is defined as set of groups. Crowd, groups and agents constitute the entiiies of the simulation. Inteniions corresponds to goals of the entities (e.g. go to the bank), beliefs represents intemal status of the entities (e.g. emotional status) while knowledge describes information of the virtual environment where the crowd is to be simulated (e.g. location of obstacles). Crowd behavior corresponds to a set of actions applied according to entities' intentions, beliefs, knowledge and perception. Finally, events represent the incidence of something causing a specific reaction, which can change the group behaviors. The problems we deal with in this paper include: I . 2. Modeling of crowd information and hierarchical structure, also concerning its distribution among groups; Different levels of realism, in order to provide simple crowd behaviors, as well as complex ones; The required structure to provide interaction with groups of agents during the simulation in real-time. The proposed solution addresses two main issues: i) crowd structure and ii) crowd behavior. Considering crowd structure, our approach deals with a hierarchy composed of crowd, groups and agents, where the groups are the most complex structure containing the information to he distributed among the individuals. Conceming crowd behavior, our virtual agents are endowed with different levels of autonomy. They can either act according to an innate and scripted crowd behavior (programmed behavior), react as a function of triggered events (reactive or autonomous behavior) or be guided by an interactive process during simulation guided behavior). We introduced the term <guided crowds> to define the groups of virtual agents that can be externally controlled in real time [I 81. The next section gives a brief overview of previous work. Section 3 discusses our model to create virtual crowds. In section 4, we introduce the programmed crowd while section 5 describes the concept of reactive behavior. Section 6 presents how to guide and interact with the guided crowds. The discussion closes with some results obtained, as well as with possible future lines of work
Musse and Thalmann REF developed virtual human agents with intentions, beliefs, knowledge and perception to create a realistic crowd behavior.
Hierarchical model for real time simulation of virtual human crowds
5th IEEE EMBS International Summer School on Biomedical Imaging, 2002.
5th IEEE EMBS International Summer School on Biomedical Imaging, 2002.
Computer Science