Data visualization benefits from non-visual cues to enable people to understand information by engaging with it through multimodality, yet most approaches rely on cumbersome technologies or large scale artifacts, making them difficult to adapt to dynamic or complex datasets. In this paper, we explore the use of cutaneous haptics as a lightweight quantitative channel for visualization tasks, allowing users to feel data and interact with it dynamically. We present Haptixel, an open-source DIY encountered-type wearable providing force-feedback on the users’ fingertips’ pulp. We propose an interaction framework illustrating how Haptixel can be used to complement visualization tasks through combinations of force levels and contact types. We evaluate our approach in a pixel-art-like VR user study (n=16) where pixels color/height are associated to forces as a univariate value mapping. Results show that participants can retrieve information with Haptixel, and significantly discriminate 3D-data with at least four levels of forces; suggesting that cutaneous force-feedback can function for quantitative distinctions in visualization tasks.

International audience

Haptic exoskeleton gloves are a widespread solution for providing force-feedback in Virtual Reality (VR), especially for 3D object manipulations. However, they are still lacking an important feature regarding in-hand haptic sensations: the palmar contact. In this paper, we present PalmEx, a novel approach which incorporates palmar force-feedback into exoskeleton gloves to improve the overall grasping sensations and manual haptic interactions in VR. PalmEx's concept is demonstrated through a self-contained hardware system augmenting a hand exoskeleton with an encountered palmar contact interface - physically encountering the users' palm. We build upon current taxonomies to elicit PalmEx's capabilities for both the exploration and manipulation of virtual objects. We first conduct a technical evaluation optimising the delay between the virtual interactions and their physical counterparts. We then empirically evaluate PalmEx's proposed design space in a user study (n=12) to assess the potential of a palmar contact for augmenting an exoskeleton. Results show that PalmEx offers the best rendering capabilities to perform believable grasps in VR. PalmEx highlights the importance of the palmar stimulation, and provides a low-cost solution to augment existing high-end consumer hand exoskeletons.

Pseudo-Haptic techniques, or visuo-haptic illusions, leverage user's visual dominance over haptics to alter the users' perception. As they create a discrepancy between virtual and physical interactions, these illusions are limited to a perceptual threshold. Many haptic properties have been studied using pseudo-haptic techniques, such as weight, shape or size. In this paper, we focus on estimating the perceptual thresholds for pseudo-stiffness in a virtual reality grasping task. We conducted a user study (n = 15) where we estimated if compliance can be induced on a non-compressible tangible object and to what extent. Our results show that (1) compliance can be induced in a rigid tangible object and that (2) pseudo-haptics can simulate beyond 24 N/cm stiffness (k > 24N/cm, between a gummy bear and a raisin, up to rigid objects). Pseudo-stiffness efficiency is (3) enhanced by the objects' scales, but mostly (4) correlated to the user input force. Taken altogether, our results offer novel opportunities to simplify the design of future haptic interfaces, and extend the haptic properties of passive props in VR.

Encountered-type of Haptic devices (ETHD) are robotic interfaces physically overlaying virtual counterparts prior to a user interaction in Virtual Reality. They theoretically reliably provide haptics in Virtual environments, yet they raise several intrinsic design challenges to properly display rich haptic feedback and interactions in VR applications. In this paper, we use a Failure Mode and Effects Analysis (FMEA) approach to identify, organise and analyse the failure modes and their causes in the different stages of an ETHD scenario and highlight appropriate solutions from the literature to mitigate them. We help justify these interfaces’ lack of deployment, to ultimately identify guidelines for future ETHD designers.

We present CoVR, a novel robotic interface providing strong kinesthetic feedback (100 N) in a room-scale VR arena. It consists of a physical column mounted on a 2D Cartesian ceiling robot (XY displacements) with the capacity of (1) resisting to body-scaled users' actions such as pushing or leaning; (2) acting on the users by pulling or transporting them as well as (3) carrying multiple potentially heavy objects (up to 80kg) that users can freely manipulate or make interact with each other. We describe its implementation and define a trajectory generation algorithm based on a novel user intention model to support non-deterministic scenarios, where the users are free to interact with any virtual object of interest with no regards to the scenarios' progress. A technical evaluation and a user study demonstrate the feasibility and usability of CoVR, as well as the relevance of whole-body interactions involving strong forces, such as being pulled through or transported.