New augmented reality (AR) techniques enable increasingly advanced modifications of body representation. This representation and its control are crucial from a social perspective, with many studies focusing on body representation in medical contexts. In this article, we propose a device that allows, in AR, the modification of the user’s appearance by controlling the width of their body. We then conduct a user study to investigate the impact of this modification on body perception, specifically its perceived affordance. Additionally, we record the participant’s internal perception (Sense of Embodiment, body-shape perception) to study their interaction with body perception. Our results show that this system can effectively modify the perceived affordances. They also highlight the strong variability of body perception and its interaction with several factors such as Sense of Embodiment and initial body perception. This work contributes to expanding knowledge of body perception within the specific context of AR and provides significant perspectives for enriching the understanding and treatment of individuals suffering from body image misperception.

Swarm fragmentation, the breakdown of communication and coordination among robots, can critically compromise a swarm's mission. Integrating Augmented Reality support into swarm monitoring-especially through co-located visualisations anchored directly on the robots- may enable human operators to detect early signs of fragmentation and intervene effectively. In this work, we propose three localised visual cues-targeting robot connectivity, dominant decision influences, and movement direction-to make explicit the underlying Perception-Decision-Action (PDA) loop of each robot. Through an immersive Virtual Reality user study, 51 participants were tasked with both anticipating potential fragmentation and selecting the appropriate control to prevent it, while observing swarms exhibiting expansion, densification, flocking, and swarming behaviours. Our results reveal that a visualisation emphasising inter-robot connectivity significantly improves anticipation of fragmentation, though none of the cues consistently enhance control selection over a baseline condition. These findings underscore the potential of co-located AR-enhanced visual feedback to support human-swarm interaction and inform the design of future AR-based supervisory systems for robot swarms. A free copy of this paper and all supplemental materials are available at https://osf.io/49gny.

In the context of robot swarms, fragmentation refers to a breakdown in communication and coordination among the robots. This fragmentation can lead to issues in the swarm self-organisation, especially the loss of efficiency or an inability to perform their tasks. Human operators influencing the swarm could prevent fragmentation. To help them in this task, it is necessary to study the ability of humans to perceive and anticipate fragmentation. This article studies the perception of different types of fragmentation occurring in swarms depending on their behaviour selected amongst swarming, flocking, expansion and densification. Thus, we characterise human perception thanks to two metrics based on the distance separating fragmented groups and the separation speed. The experimentation protocol consists of a binary discrimination task in which participants have to assess the presence of fragmentation. The results show that detecting fragmentation for expansion behaviour and anticipating fragmentation, in general, are challenging. Moreover, they show that humans rely on separation distance and speed to infer the presence or absence of fragmentation. Our study paves the way for new research that will provide information to humans to better anticipate and efficiently prevent the occurrence of swarm fragmentation.

Virtual Reality (VR) has emerged as a promising solution to address the pressing concern of transferring know-how in the manufacturing industry. Making an immersive training experience often involves designing an instrumented replica of a tool whose use is to be learned through virtual training. The process of making a replica can alter its mass, making it different from that of the original tool. As far as we know, the influence of this difference on learning outcomes has never been evaluated. To investigate this subject, an immersive training experience was designed with pre and post-training phases under real conditions, dedicated to learning the use of a rotary tool. 80 participants took part in this study, split into three groups: a control group performing the virtual training using a replica with the same mass as the original tool ($\mathrm{m}=100\%$), a second group that used a replica with a lighter mass than the original tool ($\mathrm{m}= 50\%$) and a third group using a replica heavier than the original tool ($\mathrm{m}=150\%$). Despite variations in the mass of the replica used for training, this study revealed that the learning outcomes remained comparable across all groups, while also demonstrating significant enhancements in certain performance measures, including task completion time. Overall, these findings provide useful insights regarding the design of tool replicas for immersive training.

International audience

The main use of Augmented Reality (AR) today for the general public is in applications for smartphones. In particular, social network applications allow the use of many AR filters, modifying users’ environments but also their own image. These AR filters are increasingly and frequently being used and can distort in many ways users’ facial traits. Yet, we still do not know clearly how users perceive their faces augmented by these filters. In this paper, we present a study that aims to evaluate the impact of different filters, modifying several facial features such as the size or position of the eyes, the shape of the face or the orientation of the eyebrows, or adding virtual content such as virtual glasses. These filters are evaluated via a self-evaluation questionnaire, asking the participants about the personality, emotion, appeal and intelligence traits that their distorted face conveys. Our results show relative effects between the different filters in line with previous results regarding the perception of others. However, they also reveal specific effects on self-perception, showing, inter alia, that facial deformation decreases participants’ credence towards their image. The findings of this study covering multiple factors allow us to highlight the impact of face deformation on user perception but also the specificity related to this use in AR, paving the way for new works focusing on the psychological impact of such filters.

Commonly used Head Mounted Displays (HMDs) in Augmented Reality (AR), namely Optical See-Through (OST) displays, suffer from a main drawback: their focal lenses can only provide a fixed focal distance. Such a limitation is suspected to be one of the main factors for distance misperception in AR. In this paper, we studied the use of an emerging new kind of AR display to tackle such perception issues: Retinal Projection Displays (RPDs). With RPDs, virtual images have no focal distance and the AR content is always in focus. We conducted the first reported experiment evaluating egocentric distance perception of observers using Retinal Projection Displays. We compared the precision and accuracy of the depth estimation between real and virtual targets, displayed by either OST HMDs or RPDs. Interestingly, our results show that RPDs provide depth estimates in AR closer to real ones compared to OST HMDs. Indeed, the use of an OST device was found to lead to an overestimation of the perceived distance by 16%, whereas the distance overestimation bias dropped to 4% with RPDs. Besides, the task was reported with the same level of difficulty and no difference in precision. As such, our results shed the first light on retinal projection displays' benefits in terms of user's perception in Augmented Reality, suggesting that RPD is a promising technology for AR applications in which an accurate distance perception is required.

While perceptual biases have been widely investigated in Virtual Reality (VR), very few studies have considered the challenging environment of Optical See-through Augmented Reality (OST-AR). Moreover, regarding distance perception, existing works mainly focus on the assessment of egocentric distance perception, i.e. distance between the observer and a real or a virtual object. In this paper, we study exocentric distance perception in AR, hereby considered as the distance between two objects, none of them being directly linked to the user. We report a user study (n=29) aiming at estimating distances between two objects lying in a frontoparallel plane at 2.1m from the observer (i.e. in the medium-field perceptual space). Four conditions were tested in our study: real objects on the left and on the right of the participant (called real-real), virtual objects on both sides (virtual-virtual), a real object on the left and a virtual one on the right (real-virtual) and finally a virtual object on the left and a real object on the right (virtual-real). Participants had to reproduce the distance between the objects by spreading two real identical objects presented in front of them. The main findings of this study are the overestimation (20%) of exocentric distances for all tested conditions. Surprisingly, the real-real condition was significantly more overestimated (by about 4%, p=.0166) compared to the virtual-virtual condition, i.e. participants obtained better estimates of the exocentric distance for the virtual-virtual condition. Finally, for the virtual-real/real-virtual conditions, the analysis showed a non-symmetrical behavior, which suggests that the relationship between real and virtual objects with respect to the user might be affected by other external factors. Considered together, these unexpected results illustrate the need for additional experiments to better understand the perceptual phenomena involved in exocentric distance perception with real and virtual objects.

In this paper, we present the design of ten different 3D user interactions using passive haptics and embedded in an escape game scenario in which users have to escape from a pyramid in a limited time. Our solution is innovative by its modularity, allowing interactions with virtual objects using tangible props manipulated either directly using the hands and feet or indirectly through a single prop held in the hand, in order to perform several interactions with the virtual environment (VE). We also propose a navigation technique based on the “impossible spaces” design, allowing users to naturally walk through several overlapping rooms of the VE. All together, our different interaction techniques allow the users to solve several enigmas built into a challenging scenario inside a pyramid.

The topic of distance perception has been widely investigated in Virtual Reality (VR). However, the vast majority of previous work mainly focused on distance perception of objects placed in front of the observer. Then, what happens when the observer looks on the side? In this paper, we study differences in distance estimation when comparing objects placed in front of the observer with objects placed on his side. Through a series of four experiments (n=85), we assessed participants' distance estimation and ruled out potential biases. In particular, we considered the placement of visual stimuli in the field of view, users' exploration behavior as well as the presence of depth cues. For all experiments a two-alternative forced choice (2AFC) standardized psychophysical protocol was employed, in which the main task was to determine the stimuli that seemed to be the farthest one. In summary, our results showed that the orientation of virtual stimuli with respect to the user introduces a distance perception bias: objects placed on the sides are systematically perceived farther away than objects in front. In addition, we could observe that this bias increases along with the angle, and appears to be independent of both the position of the object in the field of view as well as the quality of the virtual scene. This work sheds a new light on one of the specificities of VR environments regarding the wider subject of visual space theory. Our study paves the way for future experiments evaluating the anisotropy of distance perception in real and virtual environments.