Local Geometric Consensus: A General Purpose Point Pattern-Based Tracking Algorithm

Proceedings of ACM ISMAR 2015, Fukuoka, JapanInternational audienceWe present a method which can quickly and robustly match 2D and 3D point patterns based on their sole spatial distribution , but it can also handle other cues if available. This method can be easily adapted to many transformations such as similarity transformations in 2D/3D, and affine and perspective transformations in 2D. It is based on local geometric consensus among several local matchings and a refinement scheme. We provide two implementations of this general scheme, one for the 2D homography case (which can be used for marker or image tracking) and one for the 3D similarity case. We demonstrate the robustness and speed performance of our proposal on both synthetic and real images and show that our method can be used to augment any (textured/textureless) planar objects but also 3D objects

Practical and precise projector-camera calibration

International audienceProjectors are important display devices for large scale augmented reality applications. However, precisely calibrating projectors with large focus distances implies a trade-off between practicality and accuracy. People either need a huge calibration board or a precise 3D model [12]. In this paper, we present a practical projector-camera calibration method to solve this problem. The user only needs a small calibration board to calibrate the system regardless of the focus distance of the projector. Results show that the root-mean-squared re-projection error (RMSE) for a 450cm projection distance is only about 4mm, even though it is calibrated using a small B4 (250 × 353mm) calibration board

Développement territorial viable, capital social et capital environnemental : Quels liens ?

L’analyse des dynamiques de développement reste en grande partie le fait des sciences économiques. Ce faisant, les sphères spatiale, sociale et environnementale sont le plus souvent occultées au profit de l’étude de la croissance économique. Les interactions entre les composantes sociale et environnementale et leurs impacts sur la dynamique territoriale des communautés locales, au-delà de la pauvreté et de la détérioration environnementale, constituent un nouveau champ de réflexion. Les sciences régionales (Aydalot, 1985 ; Friedman et Weaver, 1979 ; Stöhr, 1981) et la géographie (Desmarais et Richot, 2000; Mohan et Mohan, 2002) s’intéressent d’ailleurs depuis longtemps à une approche territoriale « endogène » ou « par le bas ». De là, le paradigme de développement territorial viable (DTV), combiné à une approche humaniste du DD, constitue un cadre interprétatif pertinent pour mieux comprendre les liens entre le social et l’environnement (Gagnon, 2002; Theys, 2002). Il est ici envisagé comme une transformation sociale, caractérisée par un renouvellement du mode de gouvernance, la recherche de solutions alternatives et l’introduction de critères sociaux et culturels dans la prise de décision. Le cadre théorique s’appuie aussi sur les notions de capital social (Putman, 2001; Portes, 1988) et de capital environnemental (Costanza et al., 1997), un peu moins théorisé. En outre, à l’aide du concept de « connectivité civile », témoin de la présence de capital social dans une communauté, nous questionnons le dynamisme de la communauté en matière de valorisation de l’environnement. Le présent article tente donc d’apporter un éclairage nouveau sur les déterminants du développement territorial, suite à des recherches empiriques réalisées dans quatre territoires microrégionaux québécois (Gagnon et al., 2006).The analysis of the dynamics of development belongs, for the most part, to the domain of economics and as a result, the spatial, social and environmental dimensions are often overshadowed by the study of economic growth. However, the interactions between the social and environmental components and their impacts on the territorial dynamics of local communities, over and above those of poverty and environmental degradation, constitute new areas for reflection. Regional studies (Aydalot, 1985; Friedman et Weaver, 1979; Stöhr, 1981) and geography (Desmarais et Richot, 2000; Mohan et Mohan, 2002) have long focused on an “endogenous” or “bottom up” territorial approach to development. The paradigm of viable territorial development (VTD), combined with a humanistic approach to sustainable development (SD), provides a relevant interpretive framework for a better understanding of the links between the social and environmental dimensions of development (Gagnon, 2002; Theys, 2002). The paradigm envisaged here is one of social change characterized by a renewed mode of governance, the search for alternative solutions and the introduction of social and cultural criteria into decision-making. The theoretical framework is also based on the notions of social capital (Putman, 2001; Portes, 1988) and the somewhat less theorized environmental capital (Costanza et al., 1997). In addition, using the concept of community networks as indicator of the presence of social capital in a community, we examine community initiative regarding sustainable development. Following upon empirical research carried out in four “micro regions” of Quebec (FQRSC, Concerted Action 2005-2006), this article attempts to shed new light on the factors which determine territorial development

Voir l'invisible : de la vision par ordinateur aux réalités augmentée et Virtuelle

International audienceThis article is dedicated to the soar of virtual reality (VR) and augmented reality (AR), with a focus on present and possible medical applications. After some de nitions of the eld, the article reviews current applications by classifying them between those that tend to allow perception of invisible objects or phenomena and those that tend to allow a different perception of what is already visible. Then, from the present limitations of AR/VR technologies, the article discusses possible applications in the histotechnology field.Cet article est consacré à l'essor de la réalité virtuelle (RV) et de la réalité augmentée (RA), notamment en ce qui concerne leurs applications médicales actuelles et potentielles. Après des définitions du domaine, il fournit un panorama des applications existantes selon une classification en deux catégories : celles qui cherchent à permettre la visualisation d'objets ou de phénomènes invisibles et celles qui cherchent a contrario à percevoir différemment ce qui est d'ores et déjà visibles. a partir des limites actuelles des technologies de rV/ra, l'article discute ensuite les applications potentielles en histotechnologie

The sense of embodiment in Virtual Reality and its assessment methods

The sense of embodiment refers to the sensations of being inside, having, and controlling a body. In virtual reality, it is possible to substitute a person’s body with a virtual body, referred to as an avatar. Modulations of the sense of embodiment through modifications of this avatar have perceptual and behavioural consequences on users that can influence the way users interact with the virtual environment. Therefore, it is essential to define metrics that enable a reliable assessment of the sense of embodiment in virtual reality to better understand its dimensions, the way they interact, and their influence on the quality of interaction in the virtual environment. In this review, we first introduce the current knowledge on the sense of embodiment, its dimensions (senses of agency, body ownership, and self-location), and how they relate the ones with the others. Then, we dive into the different methods currently used to assess the sense of embodiment, ranging from questionnaires to neurophysiological measures. We provide a critical analysis of the existing metrics, discussing their advantages and drawbacks in the context of virtual reality. Notably, we argue that real-time measures of embodiment, which are also specific and do not require double tasking, are the most relevant in the context of virtual reality. Electroencephalography seems a good candidate for the future if its drawbacks (such as its sensitivity to movement and practicality) are improved. While the perfect metric has yet to be identified if it exists, this work provides clues on which metric to choose depending on the context, which should hopefully contribute to better assessing and understanding the sense of embodiment in virtual reality

Influence of Being Embodied in an Obese Virtual Body on Shopping Behavior and Products Perception in VR

Research in Virtual Reality (VR) showed that embodiment can influence participants' perceptions and behavior when embodied in a different yet plausible virtual body. In this paper, we study the changes an obese virtual body has on products perception (e.g., taste, etc.) and purchase behavior (e.g., number purchased) in an immersive virtual retail store. Participants (of a normal BMI on average) were embodied in a normal (N) or an obese (OB) virtual body and were asked to buy and evaluate food products in the immersive virtual store. Based on stereotypes that are classically associated with obese people, we expected that the group embodied in obese avatars would show a more unhealthy diet, (i.e., buy more food products and also buy more products with high energy intake, or saturated fat) and would rate unhealthy food as being tastier and healthier than participants embodied in “normal weight” avatars. Our participants also rated the perception of their virtual body: the OB group perceived their virtual body as significantly heavier and older. They also rated their sense of embodiment and presence within the immersive virtual store. These measures did not show any significant difference between groups. Finally, we asked them to rate different food products in terms of tastiness, healthiness, sustainability and price. The only difference we noticed is that participants embodied in an obese avatar (OB group) rated the coke as being significantly tastier and the apple as being significantly healthier. Nevertheless, while we hypothesized that participants embodied in a virtual body with obesity would show differences in their shopping patterns (e.g., more “unhealthy” products bought) there were no significant differences between the groups. Stereotype activation failed for our participants embodied in obese avatars, who did not exhibit a shopping behavior following the (negative) stereotypes related to obese people. conversely, while the opposite hypothesis (participants embodied in obese avatars would buy significantly more healthy products in order to “transform” their virtual bodies) could have been made, it was not the case either. We discuss these results and propose hypotheses as to why the behavior of the manipulated group differed from the one we expected. Indeed, unlike previous research, our participants were embodied in virtual avatars which differed greatly from their real bodies. Obese avatars should not only modify users' visual characteristics such as hair or skin color, etc. We hypothesize that an obese virtual body may require some other non-visual stimulus, e.g., the sensation of the extra weight or the change in body size. This main difference could then explain why we did not notice any important modification on participants' behavior and perceptions of food products. We also hypothesize that the absence of stereotype activation and thus of statistical difference between our N and OB groups might be due to higher-level cognitive processes involved while purchasing food products. Indeed our participants might have rejected their virtual bodies when performing the shopping task, while the embodiment and presence ratings did not show significant differences, and purchased products based on their real (non-obese) bodies. This could mean that stereotype activation is more complex that previously thought

Practical and precise projector-camera calibration

International audienceProjectors are important display devices for large scale augmented reality applications. However, precisely calibrating projectors with large focus distances implies a trade-off between practicality and accuracy. People either need a huge calibration board or a precise 3D model [12]. In this paper, we present a practical projector-camera calibration method to solve this problem. The user only needs a small calibration board to calibrate the system regardless of the focus distance of the projector. Results show that the root-mean-squared re-projection error (RMSE) for a 450cm projection distance is only about 4mm, even though it is calibrated using a small B4 (250 × 353mm) calibration board

A study on differences in human perception between a real and an AR scene viewed in an OST-HMD

International audienceWith the recent growth in the development of augmented reality (AR) technologies , it is becoming important to study human perception of AR scenes. In order to detect whether users will suffer more from visual and operator fatigue when watching virtual objects through optical see-through head-mounted displays (OST-HMDs), compared with watching real objects in the real world, we propose a comparative experiment including a virtual magic cube task and a real magic cube task. The scores of the subjective questionnaires (SQ) and the values of the critical flicker frequency (CFF) were obtained from 18 participants. In our study, we use several electrooculogram (EOG) and heart rate variability (HRV) measures as objective indicators of visual and operator fatigue. Statistical analyses were performed to deal with the subjective and objective indicators in the two tasks. Our results suggest that participants were very likely to suffer more from visual and operator fatigue when watching virtual objects presented by the OST-HMD. In addition, the present study provides hints that HRV and EOG measures could be used to explore how visual and operator fatigue are induced by AR content. Finally, three novel HRV measures are proposed to be used as potential indicators of operator fatigue

Effects of physical, non-immersive virtual, and immersive virtual store environments on consumers’ perceptions and purchase behavior

The application of virtual reality in human activities has been rapidly growing during the last decade. Shopping for food is an important part of people’s daily lives. As overnight delivery services of fresh produce, such as Amazon Fresh, are in their development stage, more studies on virtual stores for perishable products are needed, as the quality of fruits and vegetables (FaVs) cannot be easily assessed by consumers when virtual stores are used. This research examines the impact of a physical store, a non-immersive virtual store, and an immersive virtual store environment on consumers’ perceptions and purchase behavior toward FaVs. Experimental betweensubjects design (i.e., three groups), combined with a questionnaire survey (after-only design), was used to address the study objectives. The research found that consumers’ perceptions of FaVs in both non-immersive and immersive virtual stores (VS) are similar to those in a physical store. By contrast, consumers buy more FaVs in both non-immersive and immersive VS compared to a physical store. The findings also indicate that consumers tend to rely more on extrinsic cues (i.e., FaVs’ prices) in the immersive VS when evaluating FaVs on offer and less on intrinsic cues (e.g., FaVs’ appearance) they use in the physical store. The results have important implications for practitioners and researchers with regard to the usefulness of virtual reality for better understanding of consumer behavior

Consumer perceptions and purchase behavior toward imperfect fruits and vegetables in an immersive virtual reality grocery store

This study investigates the effects of fruits and vegetables (FaVs) abnormality on consumer perceptions and purchasing behavior. For the purposes of the study, a virtual grocery store was created with a fresh FaVs section, where 142 participants became immersed using an Oculus Rift DK2 Head-Mounted Display (HMD) software. Participants were presented either “normal”, “slightly” misshapen, “moderately” misshapen or “severely” misshapen” FaVs. The study findings indicate that shoppers tend to purchase a similar number of FaVs whatever their level of deformity. However, perceptions of the appearance and quality of the FaVs depend on the degree of abnormality. “Moderately” misshapen FaVs are perceived as significantly better than those that are “heavily” misshapen but also “slightly” misshapen (except for the appearance of fruits)