Survey of Virtual Reality Interactions via Haptic Solutions
In the past few years, the terms “Virtual Reality” and “Haptics” have been amongst the most quoted keywords in HCI conferences.
Why enabling haptics in VR?
Virtual Reality experiences are evaluated in terms of presence. Presence is the feeling of being in another place than the one we are actually in. It heavily relies on the users’ senses. Currently, immersion and realism levels in terms of vision and auditory cues are really convincing in VR. Nonetheless, the sense of touch is still behind.
The issue behind this evaluation protocol and the current implementations, is that no matter the haptic feeedback we receive in VR, it is always considered as a plus to increase presence. Indeed, current questionnaires to quantify presence are outdated and focus on graphics rendering, on vision cues. The questions regarding haptic feedback only consist in “How well could you manipulate objects in the VE?”. Hence, even a classic controller would have great results. Moreover, interfaces are often compared with a baseline that does not even involve haptics, hence the results are often expected and obviously positive.
In this paper, we emphasize the available haptic interactions and haptic features that can be potentially be provided from a haptic solution in VR, and propose a novel 2D-design space to analyse the solutions that provide these interactions. It depicts the interfaces types according to their degree of physicality, i.e. their physical consistency and level of resemblance as to replicating an object, and their degree of actuation, i.e. whether they rely on a motor-based hardware implementation enabling autonomous displacements of the interface.
This design space is useful to characterize, classify and compare haptic interactions and the corresponding haptic solutions. We also propose two criteria, User experience and Conception costs, highlighting the implicit trade-offs between the quality of the user experience and the intricacy for the designer to implement these solutions. Both of the user’s and designer’s perspectives are hence considered in a novel framework to evaluate haptic interactions. Finally, we illustrate the utility of our design space by analyzing and comparing four haptic solutions. This analysis indicates that (1) the use of real props in a virtual environment benefits the user experience, but limits the interactions to the existing props available within the VR arena; (2) the use of robotised interfaces enables more various interactions; (3) combining them offers the best user experience/design cost trade-off; (4) current evaluation methods do not allow a fair representation and comparison of haptic solutions.
We then propose guidelines to evaluate haptic interactions from both the user and designer perspectives. We also outline how intertwining interfaces can expand haptic opportunities, by conducting a deeper investigation on Robotic Graphics interfaces. Indeed, in the quest of the Ultimate Display, these show (a) the largest variety of interactions, (b) the most reliable interfaces through their automation, and (c) the most natural interactions as they encounter the users at their positions of interest without further notice.