Assessing the perceived realism of agent crowd behaviour within virtual urban environments using psychophysics

Inhabited virtual environments feature in a growing number of graphical applications. Simulated crowds are employed for different purposes; ranging from evaluation of evacuation procedures to driving interactable elements in video games. For many applications, it is important that the displayed crowd behaviour is perceptually plausible to the intended viewers. Crowd behaviour is inherently in flux, often depending upon many different variables such as location, situation and crowd composition. Researchers have, for a long time, attempted to understand and reason about crowd behaviour, going back as far as famous psychologists such as Gustave Le Bon and Sigmund Freud who applied theories of mob psychology with varying results. Since then, various other methods have been tried, from articial intelligence to simple heuristics, for crowd simulation. Even though the research into methods for simulating crowds has a long history, evaluating such simulations has received less attention and, as this thesis will show, increased complexity and high-delity recreation of recorded behaviours does not guarantee improvement in the plausibility for a human observer. Actual crowd data is not always perceived more real than simulation, making it dicult to identify gold standards, or a ground truth. This thesis presents new work on the use of psychophysics for perceptual evaluation of crowd simulation in order to develop methods and metrics for tailoring crowd behaviour for target applications. Psychophysics itself is branch of psychology dedicated to studying the relationship between a given stimuli and how it is perceived. A three-stage methodology of analysis, synthesis and perception is employed in which crowd data is gathered from the analysis of real instances of crowd behaviour and then used to synthesise behavioural features for simulation before being perceptually evaluated using psychophysics. Perceptual thresholds are calculated based on the psychometric function and key congurations are identied that appear the most perceptually plausible to human viewers. The method is shown to be useful for the initial application and it is expected that it will be applicable to a wide range of simulation problems in which human perception and acceptance is the ultimate measure of success

Assessing the perceived realism of agent grouping dynamics for adaptation and simulation

Virtual crowds are a prominent feature for a range of applications; from simulations for cultural heritage, to interactive elements in video games. A body of existing research seeks to develop and improve algorithms for crowd simulation, typically with a goal of achieving more realistic behaviours. For applications targeting human interaction however, what is judged as realistic crowd behaviour can be subjective, leading to situations where actual crowd data is not always perceived to be more real than simulation, making it difficult to identify a ground truth. We present a novel method using psychophysics to assess the perceived realism of behavioural features with respect to virtual crowds. In this instance, a focus is given to the grouping dynamics feature, whereby crowd composition in terms of group frequency and density is evaluated through thirty-six conditions based on crowd data captured from three pedestrianised real-world locations. The study, conducted with seventy-eight healthy participants, allowed for the calculation of perceptual thresholds, with configurations identified that appear most real to human viewers. The majority of these configurations correlate with the values extracted from the crowd data, with results suggesting that viewers have more perceptual flexibility when group frequency and density are increased, rather than decreased.</p

Words into Movement: the Ballet as Intersemiotic Translation

Roman Jakobson, in his 1959 article “On Linguistic Aspects of Translation”, extended the concept of translation to include transfer between different sign systems. On the basis of this definition, many ballets may be perceived as a form of intersemiotic translation, since their aesthetic structure and narrative content is largely derived from some preceding text, which may be either verbal or musical or both. This paper looks at the mechanisms involved in the transfer of meaning from the verbal into the kinesthetic code, with reference to the work of classic dance theorists such as Rudolf Laban, Doris Humphries, Merce Cunningham, etc., and to contemporary culturalist approaches. Examples are drawn from 4 different versions of Romeo and Juliet

A graphical simulator for modeling complex crowd behaviors

Abnormal crowd behaviors of varied real-world settings could represent or pose serious threat to public safety. The video data required for relevant analysis are often difficult to acquire due to security, privacy and data protection issues. Without large amounts of realistic crowd data, it is difficult to develop and verify crowd behavioral models, event detection techniques, and corresponding test and evaluations. This paper presented a synthetic method for generating crowd movements and tendency based on existing social and behavioral studies. Graph and tree searching algorithms as well as game engine-enabled techniques have been adopted in the study. The main outcomes of this research include a categorization model for entity-based behaviors following a linear aggregation approach; and the construction of an innovative agent-based pipeline for the synthesis of A-Star path-finding algorithm and an enhanced Social Force Model. A Spatial-Temporal Texture (STT) technique has been adopted for the evaluation of the model's effectiveness. Tests have highlighted the visual similarities between STTs extracted from the simulations and their counterparts - video recordings - from the real-world

Walking with virtual humans : understanding human response to virtual humanoids' appearance and behaviour while navigating in immersive VR

In this thesis, we present a set of studies whose results have allowed us to analyze how to improve the realism, navigation, and behaviour of the avatars in an immersive virtual reality environment. In our simulations, participants must perform a series of tasks and we have analyzed perceptual and behavioural data. The results of the studies have allowed us to deduce what improvements are needed to be incorporated to the original simulations, in order to enhance the perception of realism, the navigation technique, the rendering of the avatars, their behaviour or their animations. The most reliable technique for simulating avatars’ behaviour in a virtual reality environment should be based on the study of how humans behave within the environment. For this purpose, it is necessary to build virtual environments where participants can navigate safely and comfortably with a proper metaphor and, if the environment is populated with avatars, simulate their behaviour accurately. All these aspects together will make the participants behave in a way that is closer to how they would behave in the real world. Besides, the integration of these concepts could provide an ideal platform to develop different types of applications with and without collaborative virtual reality such as emergency simulations, teaching, architecture, or designing. In the first contribution of this thesis, we carried out an experiment to study human decision making during an evacuation. We were interested to evaluate to what extent the behaviour of a virtual crowd can affect individuals' decisions. From the second contribution, in which we studied the perception of realism with bots and humans performing just locomotion or varied animations, we can conclude that the combination of having human-like avatars with animation variety can increase the overall realism of a crowd simulation, trajectories and animation. The preliminary study presented in the third contribution of this thesis showed that realistic rendering of the environment and the avatars do not appear to increase the perception of realism in the participants, which is consistent with works presented previously. The preliminary results in our walk-in-place contribution showed a seamless and natural transition between walk-in-place and normal walk. Our system provided a velocity mapping function that closely resembles natural walk. We observed through a pilot study that the system successfully reduces motion sickness and enhances immersion. Finally, the results of the contribution related to locomotion in collaborative virtual reality showed that animation synchronism and footstep sound of the avatars representing the participants do not seem to have a strong impact in terms of presence and feeling of avatar control. However, in our experiment, incorporating natural animations and footstep sound resulted in smaller clearance values in VR than previous work in the literature. The main objective of this thesis was to improve different factors related to virtual reality experiences to make the participants feel more comfortable in the virtual environment. These factors include the behaviour and appearance of the virtual avatars and the navigation through the simulated space in the experience. By increasing the realism of the avatars and facilitating navigation, high scores in presence are achieved during the simulations. This provides an ideal framework for developing collaborative virtual reality applications or emergency simulations that require participants to feel as if they were in real life.En aquesta tesi, es presenta un conjunt d'estudis els resultats dels quals ens han permès analitzar com millorar el realisme, la navegació i el comportament dels avatars en un entorn de realitat virtual immersiu. En les nostres simulacions, els participants han de realitzar una sèrie de tasques i hem analitzat dades perceptives i de comportament mentre les feien. Els resultats dels estudis ens han permès deduir quines millores són necessàries per a ser incorporades a les simulacions originals, amb la finalitat de millorar la percepció del realisme, la tècnica de navegació, la representació dels avatars, el seu comportament o les seves animacions. La tècnica més fiable per simular el comportament dels avatars en un entorn de realitat virtual hauria de basar-se en l'estudi de com es comporten els humans dins de l¿entorn virtual. Per a aquest propòsit, és necessari construir entorns virtuals on els participants poden navegar amb seguretat i comoditat amb una metàfora adequada i, si l¿entorn està poblat amb avatars, simular el seu comportament amb precisió. Tots aquests aspectes junts fan que els participants es comportin d'una manera més pròxima a com es comportarien en el món real. A més, la integració d'aquests conceptes podria proporcionar una plataforma ideal per desenvolupar diferents tipus d'aplicacions amb i sense realitat virtual col·laborativa com simulacions d'emergència, ensenyament, arquitectura o disseny. En la primera contribució d'aquesta tesi, vam realitzar un experiment per estudiar la presa de decisions durant una evacuació. Estàvem interessats a avaluar en quina mesura el comportament d'una multitud virtual pot afectar les decisions dels participants. A partir de la segona contribució, en la qual estudiem la percepció del realisme amb robots i humans que realitzen només una animació de caminar o bé realitzen diverses animacions, vam arribar a la conclusió que la combinació de tenir avatars semblants als humans amb animacions variades pot augmentar la percepció del realisme general de la simulació de la multitud, les seves trajectòries i animacions. L'estudi preliminar presentat en la tercera contribució d'aquesta tesi va demostrar que la representació realista de l¿entorn i dels avatars no semblen augmentar la percepció del realisme en els participants, que és coherent amb treballs presentats anteriorment. Els resultats preliminars de la nostra contribució de walk-in-place van mostrar una transició suau i natural entre les metàfores de walk-in-place i caminar normal. El nostre sistema va proporcionar una funció de mapatge de velocitat que s'assembla molt al caminar natural. Hem observat a través d'un estudi pilot que el sistema redueix amb èxit el motion sickness i millora la immersió. Finalment, els resultats de la contribució relacionada amb locomoció en realitat virtual col·laborativa van mostrar que el sincronisme de l'animació i el so dels avatars que representen els participants no semblen tenir un fort impacte en termes de presència i sensació de control de l'avatar. No obstant això, en el nostre experiment, la incorporació d'animacions naturals i el so de passos va donar lloc a valors de clearance més petits en RV que treballs anteriors ja publicats. L'objectiu principal d'aquesta tesi ha estat millorar els diferents factors relacionats amb experiències de realitat virtual immersiva per fer que els participants se sentin més còmodes en l'entorn virtual. Aquests factors inclouen el comportament i l'aparença dels avatars i la navegació a través de l'entorn virtual. En augmentar el realisme dels avatars i facilitar la navegació, s'aconsegueixen altes puntuacions en presència durant les simulacions. Això proporciona un marc ideal per desenvolupar aplicacions col·laboratives de realitat virtual o simulacions d'emergència que requereixen que els participants se sentin com si estiguessin en la vida realPostprint (published version

Controlling Individual Agents in High-Density Crowd Simulation

Simulating the motion of realistic, large, dense crowds of autonomous agents is still a challenge for the computer graphics community. Typical approaches either resemble particle simulations (where agents lack orientation controls) or are conservative in the range of human motion possible (agents lack psychological state and aren’t allowed to ‘push’ each other). Our HiDAC system (for High-Density Autonomous Crowds) focuses on the problem of simulating the local motion and global wayfinding behaviors of crowds moving in a natural manner within dynamically changing virtual environments. By applying a combination of psychological and geometrical rules with a social and physical forces model, HiDAC exhibits a wide variety of emergent behaviors from agent line formation to pushing behavior and its consequences; relative to the current situation, personalities of the individuals and perceived social density

Multi-agent geo-simulation of crowds and control forces in conflict situations : models, application and analysis

Peu de modèles et de simulations qui décrivent les comportements de foule en situations de conflit impliquant des forces de l’ordre et des armes non-létales (NLW) existent. Ce mémoire présente des modèles d’agents de la foule et des forces de l’ordre ainsi que des NLWs dans des situations de conflit. Des groupes ainsi que leurs interactions et actions collectives sont explicitement modélisés, ce qui repousse les approches de simulation de foule existantes. Les agents sont caractérisés par des profils d’appréciation de l’agressivité et ils peuvent changer leurs comportements en relation avec la Théorie de l’identité sociale. Un logiciel a été développé et les modèles ont été calibrés avec des scénarios réalistes. Il a démontré la faisabilité technique de modèles sociaux aussi complexes pour des foules de centaines d’agents, en plus de générer des données pour évaluer l’efficacité des techniques d’intervention.Few models and simulations that describe crowd behaviour in conflict situations involving control forces and non-lethal weapons (NLW) exist. This thesis presents models for crowd agents, control forces, and NLWs in crowd control situations. Groups as well as their interactions and collective actions are explicitly modelled, which pushes further currently existing crowd simulation approaches. Agents are characterized by appreciation of aggressiveness profiles and they can change their behaviours in relation with the Social Identity theory. A software application was developed and the models were calibrated with realistic scenarios. It demonstrated the technical feasibility of such complex social models for crowds of hundreds of agents, as well generating data to assess the efficiency of intervention techniques

Social identity modelling

This is an editorial to the special section on “Social Identity Modelling”, published in Volume 26, Issues 2 and 3, 2023 of the Journal of Artificial Societies and Social Simulation. It provides information on how the Social Identity Approach (SIA) and the research using its theoretical framework explains collective behaviour, tailored specifically for modellers. The discussion centres around describing and reflecting on the state of the art in modelling SIA. The editorial ends with looking ahead towards formalising SIA as a means to enable more collective behavioural realism in agent-based social simulations.Energie and Industri

No. 66: Xenophobic Violence in South Africa: Denialism, Minimalism, Realism

Violent xenophobia has become a regular feature of South African life. Everyday animosity frequently spills over into violence against individual migrants and refugees and their economic enterprises. Some of these incidents reach the scrutiny of the media and officialdom, but most remain invisible and unremarked. The fact that most of the violence occurs in marginal urban locations of informal settlements, townships and inner-city suburbs in South Africa has prompted intense debate over the nomenclature and identification of the underlying causes. Explanations for the large-scale anti-migrant violence that swept the country in May 2008, and continues in more isolated and sporadic fashion through to the present day, fall into three general categories: “xenophobia denialism”, “xenophobia minimalism” and “xenophobia realism.” The denialists reject the argument that xenophobia plays any role in violence against migrants and refugees. The South African government, initially bewildered by the unexpectedness and ferocity of the May 2008 violence, settled on an official position that the deaths, destruction and displacement were the work of criminal elements in the affected areas. This argument that attacks on migrants and refugees are simply acts of criminality, not xenophobia, is now state orthodoxy. Xenophobia denialism has also shaped official South African responses to criticism from the international community. Violence perpetrated by the police and South African citizens continues to be explained away by politicians as criminal acts by isolated, anti-social elements. The government’s position has been echoed by some researchers and political commentators who suggest that only a very small group of individuals engage in such acts and that these are not symptomatic of wider prejudice against migrants within South African society. Another form of denialism shifts the blame from xenophobia to the state’s dereliction of its duties, particularly its failure to control borders. According to this view, the problem is that the state has not seriously engaged with the “foreign threat.” It is difficult to see how South Africa’s draconian border and immigration controls can be considered either soft or lenient. The post-apartheid state has intensified border and immigration enforcement and, even at the height of the 2008 violence, officials were deporting displaced victims they claimed had entered South Africa illegally. State agencies have typically focused on identifying irregular migrants among victims of violence and deporting them, reinforcing the biases and prejudices that fuelled the violence to begin with. The xenophobia minimalists also eschew it as an explanation for violence against migrants and refugees, seeing it instead as an epiphenomenon or symptom of a deeper malaise. This is a particularly prevalent tendency amongst neo-marxist scholars seeking a materialist explanation for the violence, which they view as the outworking of structural economic inequalities and the capture of the African National Congress by neoliberalism, with the consequent inability of the state to effect a fundamental transformation and redistribution of wealth and resources in the country. The minimalists essentially argue that although xenophobia might exist, it is an epiphenomenon that does not get at the root causes of violence. One strand of minimalism sees the violence as a signifier of a broader, deepening social crisis in South Africa tied to intense competition for scarce resources such as jobs, shelter and services. According to this view, the effects of the inadequate post-apartheid transition have been felt most acutely in marginal urban locations where much of the violence has occurred and where difference has become the site around which the palpable anger and frustrations of those left out has been expressed. Certainly, the spatial incidence of violence in May 2008 was strongly correlated with the geography of poverty. But this simply begs the question of why not all poor areas (including many in which migrants and refugees resided) erupted or why poor South Africans were not attacking each other with similar ferocity. The economic insecurity of the offenders may account for their extreme anxiety and heightened dissatisfaction, but it does not explain why only certain groups were and are singled out for deadly assault. Furthermore, if economic competition between poor residents and migrants is the underlying cause of aggressive hostility, it does not explain why wealthy and privileged groups, who do not face direct or even indirect competition from these migrants, also espouse these prejudices. When vicious attacks on migrants are conceived primarily as the outcome of material realities and economic competition between citizens and “foreigners”, then the frames of reference are automatically loaded against the latter. Seen in such terms, resentment and antipathy towards migrants and other outsiders become inevitable aspects of the social landscape, justifying stringent controls over immigration, and exclusion (or at best very limited inclusion) of migrants. This distinction invigorates the very idea that the presence of migrants and refugees poses a perpetual threat to “legitimate insiders”. Similarly, the crises of governance and frustrated hopes in South Africa, particularly at local levels, have little if anything to do with the presence of migrants. These connections need to be constructed more carefully to avoid reproducing the very prejudices that need to be confronted. One cannot deny that there is rivalry between locals and migrants. However, migrants represent a very small minority in terms of South Africa’s total population, and the detrimental effects of this economic competition have been seriously overstated. Both xenophobia denialism and xenophobia minimalism ignore or sideline the evidence that most South Africans hold extremely negative views about migrants and refugees and want the state to exercise greater coercive power to purge the country of their presence. The realists suggest, by contrast, that xenophobia is a pervasive phenomenon throughout South African society and that there is a predisposition to resort to violence on the part of a considerable number of South Africans. This viewpoint is based on systematic representative sampling of the South African population as a whole. The Southern African Migration Programme (SAMP) has been monitoring the perceptions and attitudes of South Africans towards migrants and refugees since the late 1990s. These periodic surveys provide unequivocal evidence of deep-rooted and pervasive hostility and animosity towards migrants and refugees in the country. Three general findings are of relevance to our argument: (a) the nature and strength of myths about migrant and migration; (b) the level of public endorsement of coercive state measures to keep migrants out of the country and to remove those who are present; and (c) the degree of willingness to resort to coercion and violence against migrants. In this paper, we argue that xenophobia realism is the best way to make sense of the phenomenon of extreme xenophobia, that is, the translation of hostile attitudes into violent actions. We conceptualize extreme xenophobia as a heightened form of xenophobia in which hostility and opposition to those perceived as outsiders and foreigners is strongly embedded and expressed through aggressive acts directed at migrants and refugees. South Africans hold migrants responsible for crime, bringing disease, and “stealing” jobs, services and resources and view them as being illegally in the country. Moreover, perceptions of a rapid increase in the number of migrants intensify the levels of threat attached to them. Rights and entitlements for residents are directly and in a discriminatory fashion linked to migration and citizenship status, drawing the boundaries between those who are seen to belong and others who are not. High levels of migrant antipathy lead to recurrent episodes of violence. The primary challenge for xenophobia realists is to explain why, if hostility is so widespread, violence tends to be more confined, targeted at poorer neighbourhoods in the cities. First, whether and where animosity translates into actions depends on community-specific dynamics such as the nature of local leadership, the absence of dispute resolution mechanisms and the character of policing. Second, all of the common myths about migrants are offered by residents to explain why the attacks take place. Migration myths are not epiphenomena or post-hoc rationalizations; they have powerful mobilizing and animating effects spurring those who believe them into acts of extreme xenophobia. Disowning the existence of xenophobia not only flies in the face of a large body of quantitative and qualitative research, it illustrates a continuing lack of political will to own the problem and act against one of the most destructive and anti-democratic forces in post-apartheid South Africa