Projects

We propose an approach to facilitate adjustable grip for object interaction in virtual reality. It enables the user to handle objects with a loose and firm grip using conventional controllers. Pivotal design properties were identified and evaluated in a qualitative pilot study. Two revised interaction designs with variable grip were compared to the status quo of invariable grip in a quantitative study. The users performed placing actions with all interaction modes. Performance, clutching, task load, and usability were measured. While the handling time increased slightly using variable grip, the usability score was significantly higher. No substantial differences were measured in positioning accuracy. The results lead to the conclusion that variable grip can be useful and improve realism depending on tasks, goals, and user preferences.

It is challenging to provide users with a haptic weight sensation of virtual objects in VR since current consumer VR controllers and software-based approaches such as pseudo-haptics cannot render appropriate haptic stimuli. To overcome these limitations, we developed a haptic VR controller named Triggermuscle that adjusts its trigger resistance according to the weight of a virtual object. Therefore, users need to adapt their index finger force to grab objects of different virtual weights. Dynamic and continuous adjustment is enabled by a spring mechanism inside the casing of an HTC Vive controller. In two user studies, we explored the effect on weight perception and found large differences between participants for sensing a change in trigger resistance and, thus, for discriminating virtual weights. The variations were easily distinguished and associated with weight by some participants, while others did not notice them at all. We discuss possible limitations, confounding factors, how to overcome them in future research and the pros and cons of this novel technology.

Hand interaction plays a key role in virtual reality (VR) sports. While in reality, athletes mostly rely on haptic perception when holding and throwing objects, these sensational cues can be missing or differ in virtual environments. In this work, we investigated how the visibility of a virtual hand can support players when throwing and what impact it has on the overall experience. We developed a Frisbee simulation in VR and asked 29 study participants to hit a target. We measured the throwing accuracy and self-reports of presence, disc control, and body ownership. The results show a subtle advantage of hand visibility in terms of accuracy. Visible hands further improved the subjective impression of realism, body ownership and subjective control over the disc.

When playing sports in virtual reality, foot interaction is crucial for many disciplines. We investigated how the visibility of the foot influences penalty shooting in soccer. In a between-group experiment, we asked 28 players to hit eight targets with a virtual ball. We measured the performance, task load, presence, ball control, and body ownership of inexperienced to advanced soccer players. In one condition, the players saw a visual representation of their tracked foot, which significantly improved the accuracy of the shots. Players with invisible foot needed 58% more attempts. Further, with foot visibility, the self-reported body ownership was higher.

Questionnaires are among the most common research tools in virtual reality (VR) user studies. Transitioning from virtuality to reality for giving self-reports on VR experiences can lead to systematic biases. VR allows the embedding of questionnaires into the virtual environment, which may ease participation and avoid biases. To provide a cohesive picture of methods and design choices for questionnaires in VR (inVRQ), we discuss 15 inVRQ studies from the literature and present a survey with 67 VR experts from academia and industry. Based on the outcomes, we conducted two user studies in which we tested different presentation and interaction methods of inVRQs and evaluated the usability and practicality of our design. We observed comparable completion times between inVRQs and questionnaires outside VR (nonVRQs) with higher enjoyment but lower usability for inVRQs. These findings advocate the application of inVRQs and provide an overview of methods and considerations that lay the groundwork for inVRQ design.

Providing haptic feedback in virtual reality to make the experience more realistic has become a strong focus of research in recent years. The resulting haptic feedback systems differ greatly in their technologies, feedback possibilities, and overall realism, making it challenging to compare different systems. We propose the Haptic Fidelity Framework, providing the means to describe, understand and compare haptic feedback systems. The framework locates a system in the spectrum of providing realistic or abstract haptic feedback using the Haptic Fidelity dimension. It comprises 14 criteria that either describe foundational or limiting factors. A second Versatility dimension captures the current trade-off between highly realistic but application-specific and more abstract but widely applicable feedback. To validate the framework, we compared the Haptic Fidelity score to the perceived feedback realism of evaluations from 38 papers and found a strong correlation, suggesting the framework accurately describes the realism of haptic feedback.

Room-scale mapping facilitates natural locomotion in virtual reality (VR), but it creates a problem when encountering virtual walls. In traditional video games, player avatars can simply be prevented from moving through walls. This is not possible in VR with room-scale mapping due to the lack of physical boundaries. Game design is either limited by avoiding walls, or the players might ignore them, which endangers the immersion and the overall game experience.

To prevent players from walking through walls, we propose a combination of auditory, visual, and vibrotactile feedback for wall collisions. This solution can be implemented with standard game engine features, does not require any additional hardware or sensors, and is independent of game concept and narrative. A between-group study with 46 participants showed that a large majority of players without the feedback did pass through virtual walls, while 87% of the participants with the feedback refrained from walking through walls. The study found no notable differences in game experience.