Locomotion In Virtual Reality Research Articles

Effects of invisible body and optic flow on experience of users voluntarily walking in a VR environment

Studies have demonstrated that a multi-modal virtual reality (VR) system can enhance the realism of virtual walking. However, a few studies explore the body awareness altered by visual presentation of virtual body and optic flow during locomotion in VR. This study investigated the impact of invisible body and optic flow on experience of users voluntarily walking in a camera-image VR environment. Participants wearing a head-mounted display performed six-step walking at their own timing. Three experimental conditions providing visible body and optic flow as a baseline, invisible body and optic flow, and invisible body and no flow, were conducted on three different days. We found that losing visual body per se decreased the feeling of being-there-now. However, providing continuous optic flow maintained virtual presence equivalent to the baseline in terms of immersion and natural walking, as opposed to providing discontinuous flow. We discussed these results in association with body awareness.

LoCoMoTe - A Framework for Classification of Natural Locomotion in VR by Task, Technique and Modality.

Virtual reality (VR) research has provided overviews of locomotion techniques, how they work, their strengths and overall user experience. Considerable research has investigated new methodologies, particularly machine learning to develop redirection algorithms. To best support the development of redirection algorithms through machine learning, we must understand how best to replicate human navigation and behaviour in VR, which can be supported by the accumulation of results produced through live-user experiments. However, it can be difficult to identify, select and compare relevant research without a pre-existing framework in an ever-growing research field. Therefore, this work aimed to facilitate the ongoing structuring and comparison of the VR-based natural walking literature by providing a standardised framework for researchers to utilise. We applied thematic analysis to study methodology descriptions from 140 VR-based papers that contained live-user experiments. From this analysis, we developed the LoCoMoTe framework with three themes: navigational decisions, technique implementation, and modalities. The LoCoMoTe framework provides a standardised approach to structuring and comparing experimental conditions. The framework should be continually updated to categorise and systematise knowledge and aid in identifying research gaps and discussions.

From Teleportation to Climbing: A Review of Locomotion Techniques in the Most Used Commercial Virtual Reality Applications

Exploration of virtual reality locomotion has a rich history, including in the creation of taxonomies categorising individual techniques. However, most existing research collects data from academic sources only, with both historic industry practitioner exploration and a state-of-the-art understanding of locomotion in commercial applications comparatively underexplored. This systematic software-level review of the complete locomotion options in 330 of the most used virtual reality applications released between 2016 and 2023 on the Steam, Meta, Oculus, Viveport, and SideQuest platforms highlights the trends and gaps that exist between industry and academic exploration. Results suggest a decline in the usage of teleportation, with the prevalence of titles containing at least one teleportation technique decreasing from 48% of those released in 2016 to 18% in 2023. Arm-tracked grabbing locomotion techniques such as climbing meanwhile are being increasingly adopted by practitioners, from almost unused in 3% of applications released in 2016 to over 30% in each year between 2020 and 2023. Additionally, although the tracking capabilities afforded by consumer-level head-mounted display hardware has resulted in a high exploration of room-scale tracking, the large academic focus on walking-based locomotion appears to not be shared by practitioners, where room-scale tracking instead is most often paired with conventional controller joystick sliding locomotion. Finally, temporal analysis results showing the growing number of locomotion techniques offered in an average application signifies the need for further accessibility-related locomotion research, particularly in areas beyond visual sickness mitigation. Our findings highlight the continuing evolution of locomotion in commercial virtual reality applications, with industry practitioner locomotion technique adoption rates displaying the divergent interests between industry and academia, in turn adding rigour to future locomotion selections across both domains.

Handheld controller-based locomotion in Virtual Reality as an approach to interactive music composition: insights from composers’ preferences

ABSTRACT In this paper, we propose a novel interactive composition approach in which locomotion within a virtual environment is used as a means to trigger predefined sound events, attenuations of sound parameters, immersive sound spatializations, and reverberations. To implement such an approach, we developed a virtual environment consisting of a large auditorium shaped like a nautilus, where users move via handheld controllers. We tested the proposed virtual environment and composition approach by conducting a user study with 15 expert composers, where we compared the 3 locomotion techniques most used in VR to move in a 3D virtual space using a handheld controller: continuous (i.e. walking), discrete (i.e. teleporting), and mixed movement (i.e. walking and teleporting). Our results showed a preference for the mixed locomotion technique. We provide a critical reflection on such a result as well as on various insights that arose from the composers’ comments.

Spatial Contraction Based on Velocity Variation for Natural Walking in Virtual Reality.

Virtual Reality (VR) offers an immersive 3D digital environment, but enabling natural walking sensations without the constraints of physical space remains a technological challenge. Previous VR locomotion methods, including game controller, teleportation, treadmills, walking-in-place, and redirected walking (RDW), have made strides towards overcoming this challenge. However, these methods also face limitations such as possible unnaturalness, additional hardware requirements, or motion sickness risks. This paper introduces "Spatial Contraction (SC)", an innovative VR locomotion method inspired by the phenomenon of Lorentz contraction in Special Relativity. Similar to the Lorentz contraction, our SC contracts the virtual space along the user's velocity direction in response to velocity variation. The virtual space contracts more when the user's speed is high, whereas minimal or no contraction happens at low speeds. We provide a virtual space transformation method for spatial contraction and optimize the user experience in smoothness and stability. Through SC, VR users can effectively traverse a longer virtual distance with a shorter physical walking. Different from locomotion gains, the spatial contraction effect is observable by the user and aligns with their intentions, so there is no inconsistency between the user's proprioception and visual perception. SC is a general locomotion method that has no special requirements for VR scenes. The experimental results of our live user studies in various virtual scenarios demonstrate that SC has a significant effect in reducing both the number of resets and the physical walking distance users need to cover. Furthermore, experiments have also demonstrated that SC has the potential for integration with existing locomotion techniques such as RDW.

Evaluation of visual, auditory, and olfactory stimulus-based attractors for intermittent reorientation in virtual reality locomotion

In virtual reality, redirected walking (RDW) enables users to stay within the tracking area while feeling that they are traveling in a virtual space that is larger than the physical space. RDW uses a visual attractor to the user’s sight and scene manipulation for intermittent reorientation. However, repeated usage can hinder the virtual world immersion and weaken the reorientation performance. In this study, we propose using sounds and smells as alternative stimuli to draw the user’s attention implicitly and sustain the attractor’s performance for intermittent reorientation. To achieve this, we integrated visual, auditory, and olfactory attractors into an all-in-one stimulation system. Experiments revealed that the auditory attractor caused the fastest reorientation, the olfactory attractor induced the widest angular difference, and the attractor with the combined auditory and olfactory stimuli induced the largest angular speed, keeping users from noticing the manipulation. The findings demonstrate the potential of nonvisual attractors to reorient users in situations requiring intermittent reorientation.

Long short-term memory prediction of user’s locomotion in virtual reality

Nowadays, there is still a challenge in virtual reality to obtain an accurate displacement prediction of the user. This could be a future key element to apply in the so-called redirected walking methods. Meanwhile, deep learning provides us with new tools to reach greater achievements in this type of prediction. Specifically, long short-term memory recurrent neural networks obtained promising results recently. This gives us clues to continue researching in this line to predict virtual reality user’s displacement. This manuscript focuses on the collection of positional data and a subsequent new way to train a deep learning model to obtain more accurate predictions. The data were collected with 44 participants and it has been analyzed with different existing prediction algorithms. The best results were obtained with a new idea, the use of rotation quaternions and the three dimensions to train the previously existing models. The authors strongly believe that there is still much room for improvement in this research area by means of the usage of new deep learning models.

Gait patterns during overground and virtual omnidirectional treadmill walking

BackgroundOmnidirectional treadmills (ODTs) offer a promising solution to the virtual reality (VR) locomotion problem, which describes the mismatch between visual and somatosensory information and contributes to VR sickness. However, little is known about how walking on ODTs impacts the biomechanics of gait. This project aimed to compare overground and ODT walking and turning in healthy young adults.MethodsFifteen young adults completed forward walk, 180° turn, and 360° turn tasks under three conditions: (1) overground, (2) on the Infinadeck ODT in a virtual environment without a handrail, and (3) on the ODT with a handrail. Kinematic data for all walking trials were gathered using 3D optical motion capture.ResultsOverall, gait speed was slower during ODT walking than overground. When controlling for gait speed, ODT walking resulted in shorter steps and greater variability in step length. There were no significant differences in other spatiotemporal metrics between ODT and overground walking. Turning on the ODT required more steps and slower rotational speeds than overground turns. The addition of the stability handrail to the ODT resulted in decreased gait variability relative to the ODT gait without the handrail.ConclusionWalking on an ODT resembles natural gait patterns apart from slower gait speed and shorter step length. Slower walking and shorter step length are likely due to the novelty of physically navigating a virtual environment which may result in a more conservative approach to gait. Future work will evaluate how older adults and those with neurological disease respond to ODT walking.

Effect of optical flow and user VR familiarity on curvature gain thresholds for redirected walking

Virtual reality (VR) locomotion should allow users to move freely in the virtual space while staying within the tracking area in the real space. The redirected walking (RDW) technique enables users to walk naturally in an unlimited virtual space within a limited tracking area by rotating the virtual scene view. However, conflicting visual and vestibular signals during RDW can lead to user discomfort and decreased immersion. To avoid user discomfort, an RDW gain should be within the detection threshold (DT) range. However, a large angle of walking redirection is required when physically avoiding obstacles or escaping from a narrow space, so DT expansion is necessary. In this study, to change the curvature DT range and enhance RDW performance, we proposed an optical flow (OF)-generating vection in a virtual environment. Further, we investigate methods to reduce user discomfort and increase RDW efficiency considering familiar and unfamiliar VR users. The findings showed that the introduction of OF led to a reduction in the DT range for all users, irrespective of the OF’s direction. However, conditions with OF resulted in an extended DT range for users familiar with VR while concurrently diminishing the DT range for those who were VR unfamiliar. To delve further, our analysis indicated that when both the OF and redirecting directions were identical, the RDW performance was robust to VR familiarity, whereas in opposing directions, the DT range increased for VR-familiar users. Our study findings suggested using OF for the RDW technique and extending its applicability in virtual environments.

A Systematic Literature Review of Virtual Reality Locomotion Taxonomies.

The change of the user's viewpoint in an immersive virtual environment, called locomotion, is one of the key components in a virtual reality interface. Effects of locomotion, such as simulator sickness or disorientation, depend on the specific design of the locomotion method and can influence the task performance as well as the overall acceptance of the virtual reality system. Thus, it is important that a locomotion method achieves the intended effects. The complexity of this task has increased with the growing number of locomotion methods and design choices in recent years. Locomotion taxonomies are classification schemes that group multiple locomotion methods and can aid in the design and selection of locomotion methods. Like locomotion methods themselves, there exist multiple locomotion taxonomies, each with a different focus and, consequently, a different possible outcome. However, there is little research that focuses on locomotion taxonomies. We performed a systematic literature review to provide an overview of possible locomotion taxonomies and analysis of possible decision criteria such as impact, common elements, and use cases for locomotion taxonomies. We aim to support future research on the design, choice, and evaluation of locomotion taxonomies and thereby support future research on virtual reality locomotion.

Metabolic cost and mechanical work of walking in a virtual reality emulator.

The purpose of this study was to investigate the metabolic cost (C), mechanical work, and kinematics of walking on a multidirectional treadmill designed for locomotion in virtual reality. Ten participants (5 females, body mass 67.2 ± 8.1kg, height 1.71 ± 0.07m, age 23.6 ± 1.9years, mean ± SD) walked on a Virtuix Omni multidirectional treadmill at four imposed stride frequencies: 0.70, 0.85, 1.00, and 1.15Hz. A portable metabolic system measured oxygen uptake, enabling calculation of C and the metabolic equivalent of task (MET). Gait kinematics and external, internal, and total mechanical work (WTOT) were calculated by an optoelectronic system. Efficiency was calculated either as WTOT/C or by summing WTOT to the work against sliding frictions. Results were compared with normal walking, running, and skipping. C was higher for walking on the multidirectional treadmill than for normal walking, running, and skipping, and decreased with speed (best-fit equation: C = 20.2-27.5·speed + 15.8·speed2); the average MET was 4.6 ± 1.4. Mechanical work was higher at lower speeds, but similar to that of normal walking at higher speeds, with lower pendular energy recovery and efficiency; differences in efficiency were explained by the additional work against sliding frictions. At paired speeds, participants showed a more forward-leaned trunk and higher ankle dorsiflexion, stride frequency, and duty factor than normal walking. Walking on a multidirectional treadmill requires a higher metabolic cost and different mechanical work and kinematics than normal walking. This raises questions on its use for gait rehabilitation but highlights its potential for high-intensity exercise and physical activity promotion.

“I Feel My Abs”: Exploring Non-standing VR Locomotion

Virtual Reality (VR) games and experiences predominantly have the users interact while standing or seated. However, this only represents a fraction of the full diversity of human movement. In this paper, we explore a novel non-standing approach to VR locomotion where the user performs locomotion movements in the air or only slightly touching the ground with their feet. For instance, the user may lie supine on the ground, reminiscent of the Bicycle Crunch, a core training movement common in Pilates and other forms of bodyweight exercise. Although this cannot generally replace traditional VR locomotion, it provides two benefits that we believe can be of use for specific application domains such as VR exergames: First, the user's lower body movement is not impeded by a small real-life space, allowing versatile navigation of large virtual worlds using walking, running, strafing, and jumping. Second, we allow new ways to activate parts of the body that remain passive in most existing VR interactions. We describe and discuss four different variants of the approach, and investigate two prototypes further in a qualitative user study, to better understand their strengths, weaknesses, and application potential.

PAWS: Personalized Arm and Wrist Movements With Sensitivity Mappings for Controller-Free Locomotion in Virtual Reality

Virtual Reality (VR) headsets equipped with multiple cameras enable hands-only teleportation techniques without requiring any physical controller. Hands-only teleportation is an effective alternative to controllers for navigation tasks in virtual reality - allowing users to move from one point to another instantaneously. However, the current implementation of hands-only techniques does not consider users' physical attributes (e.g., arm's reach). Thus, a hands-only teleportation technique can lead to different user experiences based on physical attributes. We propose PAWS, a personalized arm and wrist-based teleportation technique that incorporates users' physical attributes for improved teleportation experiences. We first evaluate different degrees of teleportation personalization with no-, partial, and full personalization. We find that full personalization offers faster locomotion - but at the cost of degraded performances with distant targets due to increased sensitivity. We hence further explore different combinations of mapping functions (e.g., sigmoid, quadratic) to personalize motor movements and find that asymmetric functions result in improved performance. Overall, our results show that PAWS helps users to navigate quickly in virtual environments.

Locomotion techniques with EEG signals in a virtual reality environment

The popularity of virtual reality (VR) experiences has been driven by a combination of technological advances, increased accessibility, and increased interest from both consumers and industries. VR applications are a great example of how immersive environments like Metaverse can take our perception to a new level. Locomotion is the most critical component in VR applications. Locomotion means movement from one place to another in a virtual reality environment. However, VR locomotion can have physical and psychological effects on users. These include potential adverse effects such as cybersickness (CS), eyestrain, disorientation, and psychological problems such as addiction or detachment from reality. Predicting potential problems is essential to understanding and mitigating them. A VREEG dataset was obtained to predict VR locomotion effects with thirty-two participants who completed ten locomotion techniques. This dataset used objective and subjective measures for VR locomotion tasks to assess physiological, usability, and cybersickness/predictability. A predictive model has used EEG features extracted from time, frequency, and time–frequency domains. This model achieved an accuracy of 99% from the dataset for nausea, oculomotor, and disorientation levels. It has also attracted attention due to its teleportation techniques (such as shift and blink locomotion), fast transitions, and low CS. Predictive goals provide insight into potential interests and areas where proactive action can be taken to reduce risks and maximize the benefits of virtual reality technology.

Effects of Transfer Functions and Body Parts on Body-centric Locomotion in Virtual Reality.

Body-centric locomotion allows users to control both movement speed and direction with body parts (e.g., head tilt, arm swing or torso lean) to navigate in virtual reality (VR). However, there is little research to systematically investigate the effects of body parts for speed and direction control on virtual locomotion by taking in account different transfer functions(L: linear function, P: power function, and CL: piecewise function with constant and linear function). Therefore, we conducted an experiment to evaluate the combinational effects of the three factors (body parts for direction control, body parts for speed control, and transfer functions) on virtual locomotion. Results showed that (1) the head outperformed the torso for movement direction control in task completion time and environmental collisions; (2) Arm-based speed control led to shorter traveled distances than both head and knee. Head-based speed control had fewer environmental collisions than knee; (3) Body-centric locomotion with CL function was faster but less accurate than both L and P functions. Task time significantly decreased from P, L to CL functions, while traveled distance and overshoot significantly increased from P, L to CL functions. L function was rated with the highest score of USE-S, -pragmatic and -hedonic; (4) Transfer function had a significant main effect on motion sickness: the participants felt more headache and nausea when performing locomotion with CL function. Our results provide implications for body-centric locomotion design in VR applications.

Acquisition and retention of spatial knowledge through virtual reality experiences: Effects of VR setup and locomotion technique

The fidelity level of virtual reality (VR) setups can affect different aspects of virtual experiences, but its effects on knowledge acquisition and retention need clarification. The two studies in this paper focus on spatial knowledge. The first study compared three VR setups, one using a VR headset and two using a tablet, differing in display and interaction fidelity. Since the type of virtual environment (VE), and the locomotion technique employed to explore it, might affect spatial knowledge acquisition, we studied each setup in an indoor and an outdoor VE with two widely used locomotion techniques (teleport and steering). Results showed that setups offering higher display and interaction fidelity can improve acquisition of spatial knowledge in terms of distance estimations (with teleport in the indoor VE, and with steering in the outdoor VE) and object-to-object spatial relations (with steering in the outdoor VE), but not in terms of object locations. This can provide guidance about how to choose the appropriate combination of setup and locomotion technique based on the type of VE and the types of spatial knowledge to acquire. Moreover, sickness and usability results showed that VR headset was more usable than tablet, and suggest using teleport on VR headset and steering on tablet. Therefore, the second study focused on VR headset with teleport and tablet with steering, and extended the assessment of their effects to spatial knowledge retention after two weeks. Results showed that spatial knowledge decreased in both conditions, but the VR headset with teleport led to better acquisition and 2-weeks retention of distance estimations.

Seamless-walk: natural and comfortable virtual reality locomotion method with a high-resolution tactile sensor

Seamless-walk: natural and comfortable virtual reality locomotion method with a high-resolution tactile sensor

Haptic Ankle Platform for Interactive Walking in Virtual Reality

This article presents an impedance type ankle haptic interface for providing users with an immersive navigation experience in virtual reality (VR). The ankle platform, actuated by an electric motor with feedback control, enables the use of foot-tapping gestures to create a walking experience like a real one and to haptically render different types of walking terrains. Experimental studies demonstrated that the interface can be easily used to generate virtual walking and is capable of rendering terrains, such as hard and soft surfaces, and multi-layer complex dynamic terrains. The designed system is a seated-type VR locomotion interface, therefore allowing its user to maintain a stable seated posture to comfortably navigate a virtual scene.

A comparison of virtual reality locomotion techniques in indoor environments

A comparison of virtual reality locomotion techniques in indoor environments

Virtual Reality Locomotion in Place for Virtual Museum Exhibitions of Culture Heritage: Comparing Joystick Controller, Point & Teleport and Arm Swinging

Locomotion methods are user interaction approaches that assist users in navigating the virtual environment when using virtual reality display device of HMDs (head-mounted displays). Most previous studies have been focused on the locomotion techniques with joystick and teleport in general and gaming context. However, there are lack study of locomotion techniques in virtual museum for context of culture heritage. In this study, this paper presents a comparative evaluation with sixty participants of the three locomotions: Joystick Controller, Point & Teleport and Arm Swinging to measure sickness, presence and flow state. In order to evaluate, this paper developed the virtual museum of Himmapan animals (https://angkaew.com/Hinmapan_vr/) which consisted of digital paint art, digitization objects, animation and digitization books. The results showed that Point & teleport less sickness of nausea than other techniques and Point & teleport also highest in perceived enjoyment than other techniques. However, we found no significant difference in presence. Finally, this paper suggested implementing Point & Teleport locomotion techniques in the application of virtual museums