International audience

Teleportation, a widely-used locomotion technique in Virtual Reality (VR), allows instantaneous movement within VR environments. Enhanced hand tracking in modern VR headsets has popularized hands-only teleportation methods, which eliminate the need for physical controllers. However, these techniques have not fully explored the potential of bi-manual input, where each hand plays a distinct role in teleportation: one controls the teleportation point and the other confirms selections. Additionally, the influence of users’ posture, whether sitting or standing, on these techniques remains unexplored. Furthermore, previous teleportation evaluations lacked assessments based on established human motor models such as Fitts’ Law. To address these gaps, we conducted a user study $( \mathrm{N}=20)$ to evaluate bi-manual pointing performance in VR teleportation tasks, considering both sitting and standing postures. We proposed a variation of the Fitts’ Law model to accurately assess users’ teleportation performance. We designed and evaluated various bi-manual teleportation techniques, comparing them to uni-manual and dwell-based techniques. Results showed that bi-manual techniques, particularly when the dominant hand is used for pointing and the non-dominant hand for selection, enable faster teleportation compared to other methods. Furthermore, bi-manual and dwell techniques proved significantly more accurate than uni-manual teleportation. Moreover, our proposed Fitts’ Law variation more accurately predicted users’ teleportation performance compared to existing models. Finally, we developed a set of guidelines for designers to enhance VR teleportation experiences and optimize user interactions.

Touchscreen is the primary solution to interact with public devices such as Automated Teller Machines (ATMs). However, the touch modality raises health concerns since users have to touch the screens, and therefore risking the spread of contagious diseases. We design PalmSpace, an alternate input technique leveraging users’ hand palms to interact with public devices. With Palmspace, UI elements are mapped onto the users’ palms and can be accessed by touching various locations directly on the palm. We conduct a series of user studies to evaluate several design options, such as interface layout, item size, preferred item location, and suitable feedback for items. Based on the results, we design PalmSpace and compare its performance with mid-air input. We show that PalmSpace is a potential solution to interact with public devices without using their touchscreen. We conclude with design guidelines for using the palm as an alternative input space for touchscreen devices.

Large curved displays are becoming increasingly popular due to their ability to provide users with a wider field of view and a more immersive experience compared to flat displays. Current interaction techniques for large curved displays often assume a user is positioned at the display's centre, crucially failing to accommodate general use conditions where the user may move during use. In this work, we investigated how user position impacts pointing interaction on large curved displays and evaluated cursor enhancement techniques to provide faster and more accurate performance across positions. To this effect, we conducted two user studies. First, we evaluated the effects of user position on pointing performance on a large semi-circular display (3m-tall, 3270R curvature) through a 2D Fitts' Law selection task. Our results indicate that as users move away from the display, their pointing speed significantly increases (at least by 9%), but accuracy decreases (by at least 6%). Additionally, we observed participants were slower when pointing from laterally offset positions. Secondly, we explored which pointing techniques providing motor- and visual-space enhancements best afford effective pointing performance across user positions. Across a total of six techniques tested, we found that a combination of acceleration and distance-based adjustments with cursor enlargement significantly improves target selection speed and accuracy across different user positions. Results further show techniques with visual-space enhancements (e.g., cursor enlargement) are significantly faster and more accurate than their non-visually-enhanced counterparts. Based on our results we provide design recommendations for implementing cursor enhancement techniques for large curved displays.

Large curved displays have emerged as a powerful platform for collaboration, data visualization, and entertainment. These displays provide highly immersive experiences, a wider field of view, and higher satisfaction levels. Yet, large curved displays are not commonly available due to their high costs. With the recent advancement of Head Mounted Displays (HMDs), large curved displays can be simulated in Virtual Reality (VR) with minimal cost and space requirements. However, to consider the virtual display as an alternative to the physical display, it is necessary to uncover user performance differences (e.g., pointing speed and accuracy) between these two platforms. In this paper, we explored users’ pointing performance on both physical and virtual large curved displays. Specifically, with two studies, we investigate users’ performance between the two platforms for standard pointing factors such as target width, target amplitude as well as users’ position relative to the screen. Results from user studies reveal no significant difference in pointing performance between the two platforms when users are located at the same position relative to the screen. In addition, we observe users’ pointing performance improves when they are located at the center of a semi-circular display compared to off-centered positions. We conclude by outlining design implications for pointing on large curved virtual displays. These findings show that large curved virtual displays are a viable alternative to physical displays for pointing tasks.

Virtual Reality (VR) headsets equipped with multiple cameras enable hands-only teleportation techniques without requiring any physical controller. Hands-only teleportation is an effective alternative to controllers for navigation tasks in virtual reality - allowing users to move from one point to another instantaneously. However, the current implementation of hands-only techniques does not consider users' physical attributes (e.g., arm's reach). Thus, a hands-only teleportation technique can lead to different user experiences based on physical attributes. We propose PAWS, a personalized arm and wrist-based teleportation technique that incorporates users' physical attributes for improved teleportation experiences. We first evaluate different degrees of teleportation personalization with no-, partial, and full personalization. We find that full personalization offers faster locomotion - but at the cost of degraded performances with distant targets due to increased sensitivity. We hence further explore different combinations of mapping functions (e.g., sigmoid, quadratic) to personalize motor movements and find that asymmetric functions result in improved performance. Overall, our results show that PAWS helps users to navigate quickly in virtual environments.

Large curved displays inside Virtual Reality environments are becoming popular for visualizing high-resolution content during analytical tasks, gaming or entertainment. Prior research showed that such displays provide a wide field of view and offer users a high level of immersion. However, little is known about users' performance (e.g., pointing speed and accuracy) on them. We explore users' pointing performance on large virtual curved displays. We investigate standard pointing factors (e.g., target width and amplitude) in combination with relevant curve-related factors, namely display curvature and both linear and angular measures. Our results show that the less curved the display, the higher the performance, i.e., faster movement time. This result holds for pointing tasks controlled via their visual properties (linear widths and amplitudes) or their motor properties (angular widths and amplitudes). Additionally, display curvatures significantly affect the error rate for both linear and angular conditions. Furthermore, we observe that curved displays perform better or similar to flat displays based on throughput analysis. Finally, we discuss our results and provide suggestions regarding pointing tasks on large curved displays in VR.

Advancements in eye-tracking technology has compelled researchers to explore potential eye-based interactions with diverse devices. Though many commercial devices are now equipped with eye-tracking solutions (e.g., HTC VIVE Pro), little is known about users social acceptance and preference of eye-based interaction techniques, especially with smartphones. We report on three studies to explore users’ social acceptance and preferences regarding different head- and eye-based inputs with smartphones. Study results show that eye movements are more socially acceptable than other head- and eye-based techniques due to its subtle nature. Based on these findings, we further examine users preferences regarding saccade and pursuit eye movements. Results reveal users’ preference for saccade compared to pursuit eye movements. In a third study exploring delimiting actions to discriminate between intentional and unintentional eye-inputs, Dwell is shown as the preferred delimiter, both in public and private spaces. We conclude with design guidelines for eye-based interactions on smartphones.

Hierarchy structures such as file systems are widespread interfaces for item retrieval and selection tasks. Some hierarchies can be modified by end-users, such as application launchers on smartphones or pictures in a file folder. These modifiable hierarchies cannot benefit from an optimization made beforehand as their content, unknown during the design process, is constantly evolving. We hence propose an analytic model which designers can integrate in their system to recommend a range of local structure modifications (e.g., creating new folders) to end-users. Proposing a range of modifications gives flexibility to end-users regarding their own meaningful grouping and labeling choices to follow a recommendation. A first experiment confirms that the recommendations built on our model can lead to modified hierarchies resulting in faster theoretical selection times. A second experiment confirms that the theoretical selection times fit empirical selection times in different hierarchy visual layouts: linear, radial, and grid.

Autostereograms are 2D images that can reveal 3D content when viewed with a specific eye convergence, without using extra-apparatus. We contribute to autostereogram studies from an HCI perspective. We explore touch inputs and output design options when interacting with autostereograms on smartphones. We found that an interactive help (i.e. to control the autostereogram stereo-separation), a color-based feedback (i.e. highlight of the screen), and a direct touch input can provide support for faster and more accurate interaction than a static help (i.e. static dots indicating the stereo-separation), an animated feedback (i.e., a 'pressed' effect), and an indirect input. In addition, results reveal that participants learn to perceive smaller and smaller autostereogram content faster with practice. This learning effect transfers across display devices (smartphone to desktop screen).

Current gesture interaction paradigm mainly involves a one-to-one gesture-command mapping. This leads to memorability issues regarding (1) the mapping - as each new command requires a new gesture, and (2) the gestures specifics (e.g., motion paths) - that can be complex to leverage the recognition of several gestures. We explore the concept of combining 3D gestures when interacting in smart environments. We first propose a design space to characterize the temporal and spatial combination aspects, and the gesture types used by the combination. We then report results from three user studies in the context of smart TV interaction. The first study reveals that end-users can create gesture sets with combinations fully optimized to reuse gestures. The second study shows that combining gestures can lead to improved memorability compared to single gestures. The third study reveals that preferences for gestures combination appear when single gestures have an abstract gesture-command mapping.

Smartwatches enable rapid access to information anytime and anywhere. However, current smartwatch content navigation techniques, for panning and zooming, were directly adopted from those used on smartphones. These techniques are cumbersome when performed on small smartwatch screens and have not been evaluated for their support in mobility and encumbrance contexts (when the user's hands are busy). We studied the effect of mobility and encumbrance on common content navigation techniques and found a significant decrease in performance as the pace of mobility increases or when the user was encumbered with busy hands. Based on these initial findings, we proposed a design space which would improve efficiency when navigation techniques, such as panning and zooming, are employed in mobility contexts. Our results reveal that our design space can effectively be used to create novel interaction techniques that improve smartwatch content navigation in mobility and encumbrance contexts.

We propose the concept of a guiding system specifically designed for semaphoric gaze gestures, i.e. gestures defining a vocabulary to trigger commands via the gaze modality. Our design exploration considers fundamental gaze gesture phases: Exploration, Guidance, and Return. A first experiment reveals that Guidance with dynamic elements moving along 2D paths is efficient and resistant to visual complexity. A second experiment reveals that a Rapid Serial Visual Presentation of command names during Exploration allows for more than 30% faster command retrievals than a standard visual search. To resume the task where the guide was triggered, labels moving from the outward extremity of 2D paths toward the guide center leads to efficient and accurate origin retrieval during the Return phase. We evaluate our resulting Gaze Gesture Guiding system, G3, for interacting with distant objects in an office environment using a head-mounted display. Users report positively on their experience with both semaphoric gaze gestures and G3.

Dynamic symbolic in-air hand gestures are an increasingly popular means of interaction with smart environments. However, novices need to know what commands are available and which gesture to execute in order to trigger these commands. We propose to adapt OctoPocus, a 2D gesture guiding system, to the case of 3D. The OctoPocus3D guidance system displays a set of 3D gestures as 3D pipes and allows users to understand how the system processes gesture input. Several feedback and feedforward visual alternatives are proposed in the literature. However, their impact on guidance remains to be evaluated. We report the results of two user experiments that aim at designing OctoPocus3D by exploring these alternatives. The results show that a concurrent feedback, which visually simplifies the 3D scene during the execution of the gesture, increases the recognition rate, but only during the first two repetitions. After the first two repetitions, users achieve the same recognition rate with a terminal feedback (after the execution of the gesture), a concurrent feedback, both or neither. With respect to feedforward, the overall stability of the 3D scene explored through the origin of the pipes during the execution of the gestures does not influence the recognition rate or the execution time. Finally, the results also show that displaying upcoming portions of the gestures allows 8% faster completion times than displaying the complete remaining portions. This indicates that preventing visual clutter of the 3D scene prevails over gesture anticipation.

We address the problem of mobile distal selection of physical objects when pointing at them in augmented environments. We focus on the disambiguation step needed when several objects are selected with a rough pointing gesture. A usual disambiguation technique forces the users to switch their focus from the physical world to a list displayed on a handheld device's screen. In this paper, we explore the balance between change of users' focus and performance. We present two novel interaction techniques allowing the users to maintain their focus in the physical world. Both use a cycling mechanism, respectively performed with a wrist rolling gesture for P2Roll or with a finger sliding gesture for P2Slide. A user experiment showed that keeping users' focus in the physical world outperforms techniques that require the users to switch their focus to a digital representation distant from the physical objects, when disambiguating up to 8 objects.