Fidelity describes how closely a replication resembles the original. It can be helpful to analyze how faithful interactions in virtual reality (VR) are to a reference interaction. In prior research, fidelity has been restricted to the simulation of reality—also called realism. Our definition includes other reference interactions, such as superpowers or fiction. Interaction fidelity is a multilayered concept. Unfortunately, different aspects of fidelity have either not been distinguished in scientific discourse or referred to with inconsistent terminology. Therefore, we present the Interaction Fidelity Model (IntFi Model). Based on the human-computer interaction loop, it systematically covers all stages of VR interactions. The conceptual model establishes a clear structure and precise definitions of eight distinct components. As a communication tool, it helps teams to understand and discuss fidelity in VR. It was reviewed through workshops with fourteen VR experts. We provide guidelines, diverse examples, and educational material to apply the IntFi Model universally to any VR experience and propose foundational research opportunities.

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.

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 improved the accuracy of the shots significantly. Players with invisible foot needed 58% more attempts. Further, with foot visibility the self-reported body ownership was higher.

The use of voice assistants (VAs) is spreading widely. Most common VAs consist of a single, usually female voice that responds to the user’s inquiry. We designed a VA system appearing as a group of agents, each with a different voice and a specialized task domain. We conducted a quantitative user study comparing our multi-agent approach with a conventional single-agent assistant in a smart home scenario as virtual reality (VR) simulation. The results show significantly higher user experience ratings for the multi-agent concept. Based on our findings, we discuss the potentials and challenges of designing multi-party VA systems.

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 to embed 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.

We propose an approach to facilitate adjustable grip for object interaction in virtual reality. It enables the user to handle objects with 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 preference.

Digital home assistants have an increasing influence on our everyday lives. The media now reports how children adapt the consequential, imperious language style when talking to real people. As a response to this behavior, we considered a digital assistant rebuking impolite language. We then investigated how adult users react when being rebuked by the AI. In a between-group study (N = 20), the participants were being rejected by our fictional speech assistant "Eliza" when they made impolite requests. As a result, we observed more polite behavior. Most test subjects accepted the AI's demand and said "please" significantly more often. However, many participants retrospectively denied Eliza the entitlement to politeness and criticized her attitude or refusal of service.

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.

Many virtual and mixed reality games focus on single player experiences. In this paper, we describe the concept and prototype implementation of a mixed reality multiplayer game that can be played with a smartphone and an HMD in outdoor environments. Players can team up to fight against attacking alien drones. The relative positions between the players are tracked using GPS, and the rear camera of the smartphone is used to augment the environment and teammates with virtual objects. The combination of multiplayer, mixed reality, the use of geographical location and outdoor action together with affordable, mobile equipment enables a novel strategic and social game experience.