In absence of haptic feedback, the perception of contact with virtual objects can rapidly become a problem in extended reality (XR) applications. XR developers often rely on visual feedback to inform the user and display contact information. However, as for today, there is no clear path on how to design and assess such visual techniques. In this paper, we propose a design space for the creation of visual feedback techniques meant to represent contact with virtual surfaces in XR. Based on this design space, we conceived a set of various visual techniques, including novel approaches based on onomatopoeia and inspired by cartoons, or visual effects based on physical phenomena. Then, we conducted an online preliminary user study with 60 participants, consisting in assessing 6 visual feedback techniques in terms of user experience. We could notably assess, for the first time, the potential influence of the interaction context by comparing the participants’ answers in two different scenarios: industrial versus entertainment conditions. Taken together, our design space and initial results could inspire XR developers for a wide range of applications in which the augmentation of contact seems prominent, such as for vocational training, industrial assembly/maintenance, surgical simulation, videogames, etc.

In this article, we propose an approach towards an infinite surface haptic display. Our approach, named ENcountered-Type ROtating Prop Approach (ENTROPiA) is based on a cylindrical spinning prop attached to a robot's end-effector serving as an encountered-type haptic display (ETHD). This type of haptic display permits the users to have an unconstrained, free-hand contact with a surface being provided by a robotic device for the users' to encounter a surface to be touched. In our approach, the sensation of touching a virtual surface is given by an interaction technique that couples with the sliding movement of the prop under the users' finger by tracking their hand location and establishing a path to be explored. This approach enables large motion for a larger surface rendering, permits to render multi-textured haptic feedback, and leverages the ETHD approach introducing large motion and sliding/friction sensations. As a part of our contribution, a proof of concept was designed for illustrating our approach. A user study was conducted to assess the perception of our approach showing a significant performance for rendering the sensation of touching a large flat surface. Our approach could be used to render large haptic surfaces in applications such as rapid prototyping for automobile design.

Encountered-Type Haptic Displays (ETHDs) represent a field of haptic displays with the premise of not using any type of actuator directly in contact with the user skin, thus providing an alternative integration of haptic displays in virtual environments. In this paper, we present novel interaction techniques (ITs) dedicated to ETHDs. The techniques aim at addressing the issues commonly presented for these devices such as limited contact areas, lags and unexpected collisions with the user. First, our paper proposes a design framework based on several parameters defining the interactive process between user and ETHD (input, movement control, displacement and contact). Five techniques based on different ramifications of the design space framework were conceived, respectively named: Swipe, Drag, Clutch, Bubble and Follow. Then, a use-case scenario was designed to depict the usage of these techniques on the task of touching and coloring a wide, flat surface. Finally, a user study based on the coloring task was conducted to assess the performance and user experience for each IT. Results were in favor of Drag and Clutch techniques which are based on manual surface displacement, absolute position selection and intermittent contact interaction. Taken together our results and design methodology pave the way to the design of future ITs for ETHDs in virtual environments.

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.