Abstract: With 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.
Our paper about the influence of being embodied in a standard or obese stereotype avatar on food purchase habits has been published in Frontiers in Robotics and AI: Virtual Environments.
This work is a collaboration between our team, Audencia Business School and Keio University.
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.
A new book is out! it is co-edited with my colleagues and friends Bruno Arnaldi and Pascal Guitton. Around 30 persons have participated to this book. It is jointly published by ISTE and Wiley.
Virtual Reality (VR) and Augmented Reality (AR) are two expressions that have recently appeared in the media but which remain largely unknown to the general public and professional world. This book aims to improve our understanding of these technologies by exploring the way in which they function and the applications we can expect for future users.
VR and AR have existed for a long time but have primarily been limited, until now, to the research domain and a few large companies. The emergence of new low-cost devices (HMDs, sensors, etc.) has led to the rise of new applications for the wider public.
In order to appreciate the advantages these new technologies bring, as well as the flaws which remain to be rectified, this book defines fundamental concepts and describes practical usage examples. These recent technological developments are then placed within a temporal dynamic by recalling the major evolutions of the past ten years and by providing some prospective avenues for the future.
our paper on the study of consumer purchase behavior with regard to non standard fruit and vegetables in VR has been accepted as a long paper to IEEE VR.
Reference: Verhulst, A.; Normand, J.M. ; Lombart, C. & Moreau, G. (2017) A Study on the Use of an Immersive Virtual Reality Store to Investigate Consumer Perceptions and Purchase Behavior toward Non-standard Fruits and Vegetables. to appear into the proceedings of IEEE Virtual Reality. Los Angeles, CA.
Abstract: In this paper we present an immersive virtual reality user study aimed at investigating how customers perceive and if they would purchase non standard (i.e. misshaped) fruits and vegetables (FaVs) in supermarkets and hypermarkets. Indeed, food waste is a major issue for the retail sector and a recent trend is to reduce it by selling non-standard goods. An important question for retailers relates to the FaVs’ “level of abnormality” that consumers would agree to buy. However, this question cannot be tackled using “classical” marketing techniques that perform user studies within real shops since fresh produce such as FaVs tend to rot rapidly preventing studies to be repeatable or to be run for a long time. In order to overcome those limitations, we created a virtual grocery store with a fresh FaVs section where 142 participants were immersed using an Oculus Rift DK2 HMD. Participants were presented either “normal”, “slightly misshaped”, “misshaped” or “severely misshaped” FaVs. Results show that participants tend to purchase a similar number of FaVs whatever their deformity. Nevertheless participants’ perceptions of the quality of the FaV depend on the level of abnormality.
Our paper on 3D reconstruction of Surface of Revolution from dense SLAM has been accepted for oral presentation at 3D Vision conference held in Stanford University.
Reference: Yang, L.; Uchuyama, H.; Normand, J.M.; Moreau, G.; Nagahara, H. & Taniguchi, R. (2016) Real-time surface of revolution reconstruction on dense SLAM. International conference on 3D Vision. Stanford, Palo Alto, CA, USA.
Abstract: We present a fast and accurate method for reconstructing surfaces of revolution (SoR) on 3D data and its application to structural modeling of a cluttered scene in real-time. To estimate a SoR axis, we derive an approximately linear cost function for fast convergence. Also, we design a framework for reconstructing SoR on dense SLAM. In the experiment results, we show our method is accurate, robust to noise and runs in real-time.
Our paper about precise and fast calibration of projector camera systems for augmented reality has been accepted for publication at ISMAR 2016, Merida.
Yang, L. ; Normand, J.M. & Moreau, G. (2016) Practical and precise projector-camera calibration. IEEE ISMAR 2016, Merida, Mexico.
abstract: Projectors 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. 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 (250x353mm) calibration board.