Locomotion In Virtual Environments Research Articles

A novel low cybersickness dynamic rotation gain enhancer based on spatial position and orientation in virtual environments

AbstractHardware and software resources nowadays make possible new Virtual Reality (VR) interaction methods. Numerous challenges have been involved over the years, and one of the most interesting is locomotion in virtual environments. In particular, Real Walking (RW) is one of the most effective Virtual Locomotion Techniques (VLT). It causes only reduced cybersickness, but it also requires proportional real walkable space to the virtual one, often requiring wide areas. In this context, optimization techniques have been proposed in the literature, e.g., reorientation or relocation. In this work, a novel method for improving reorientation in a virtual environment, exploiting a dynamic Rotation Gain Multiplication Factor (RGMF) based on the competence of the user in VR systems usage is proposed. The results highlight the effectiveness of the system and show the specific target of users that mainly appreciated it.

Comparing hand gestures and a gamepad interface for locomotion in virtual environments

Hand gesture is a new and promising interface for locomotion in virtual environments. While several previous studies have proposed different hand gestures for virtual locomotion, little is known about their differences in terms of performance and user preference in virtual locomotion tasks. In the present paper, we presented three different hand gesture interfaces and their algorithms for locomotion, which are called the Finger Distance gesture, the Finger Number gesture and the Finger Tapping gesture. These gestures were inspired by previous studies of gesture-based locomotion interfaces and are typical gestures that people are familiar with in their daily lives. Implementing these hand gesture interfaces in the present study enabled us to systematically compare the differences between these gestures. In addition, to compare the usability of these gestures to locomotion interfaces using gamepads, we also designed and implemented a gamepad interface based on the Xbox One controller. We conducted empirical studies to compare these four interfaces through two virtual locomotion tasks. A desktop setup was used instead of sharing a head-mounted display among participants due to the concern of the Covid-19 situation. Through these tasks, we assessed the performance and user preference of these interfaces on speed control and waypoints navigation. Results showed that user preference and performance of the Finger Distance gesture were close to that of the gamepad interface. The Finger Number gesture also had close performance and user preference to that of the Finger Distance gesture. Our study demonstrates that the Finger Distance gesture and the Finger Number gesture are very promising interfaces for virtual locomotion. We also discuss that the Finger Tapping gesture needs further improvements before it can be used for virtual walking.

Locomotion in virtual environments predicts cardiovascular responsiveness to subsequent stressful challenges

Individuals differ in their physiological responsiveness to stressful challenges, and stress potentiates the development of many diseases. Heart rate variability (HRV), a measure of cardiac vagal break, is emerging as a strong index of physiological stress vulnerability. Thus, it is important to develop tools that identify predictive markers of individual differences in HRV responsiveness without exposing subjects to high stress. Here, using machine learning approaches, we show the strong predictive power of high-dimensional locomotor responses during novelty exploration to predict HRV responsiveness during stress exposure. Locomotor responses are collected in two ecologically valid virtual reality scenarios inspired by the animal literature and stress is elicited and measured in a third threatening virtual scenario. Our model’s predictions generalize to other stressful challenges and outperforms other stress prediction instruments, such as anxiety questionnaires. Our study paves the way for the development of behavioral digital phenotyping tools for early detection of stress-vulnerable individuals.

Magic Carpet: Interaction Fidelity for Flying in VR.

Locomotion in virtual environments is currently a difficult and unnatural task to perform. Normally, researchers tend to devise ground- or floor-based metaphors to constrain the degrees of freedom (DoFs) during motion. These restrictions enable interactions that accurately emulate the human gait to provide high interaction fidelity. However, flying allows users to reach specific locations in a virtual scene more expeditiously. Our experience suggests that even though flying is not innate to humans, high-interaction-fidelity techniques may also improve the flying experience since flying requires simultaneously controlling additional DoFs. We present the Magic Carpet, an approach to flying that combines a floor proxy with a full-body representation to avoid balance and cybersickness issues. This design space enables DoF separation by treating direction indication and speed control as two separate phases of travel, thereby enabling techniques with higher interaction fidelity. To validate our design space, we conducted two complementary studies, one for each of the travel phases. In this paper, we present the results of both studies and report the best techniques for use within the Magic Carpet design space. To this end, we use both objective and subjective measures to evaluate the efficiency, embodiment effect, and side effects, such as physical fatigue and cybersickness, of the tested techniques in our design space. Our results show that the proposed approach enables high-interaction-fidelity techniques while improving the user experience.

Hip-directed walking-in-place using a single depth camera

Abstract Walking-in-place (WIP) is a locomotion technique that allows users to travel in virtual environments (VEs) without significantly changing their physical position on the floor. Hip-directed steering(HDS) is a novel physical technique for controlling direction changes in virtual travel using hip movements. We present an WIP-based navigation approach for controlling locomotion in VEs that combines the speed and direction in a scenario similar to a domestic setup in which people interact with a flat screen. Their physical motion data are captured by one depth camera properly aligned with the screen and oriented toward the user. We approach the characteristically noisy data generated by depth cameras via a user study to determine both the range of values and their robustness from the motion data associated with the joints relevant to WIP speed(knee, ankle and foot) and HDS (spine, hip and shoulder) to derive a reliable technique. Our WIP speed method is supported in a simple vocabulary of five different footstep types. Experimental results show that both the knee and hip provide the most robust data. We evaluated our techniques via usability tests exercising common locomotion tasks. The results show that users liked both the speed control and comfort afforded by our speed method. Regarding HDS, users reported that the angular-based method allowed them to travel faster and was both more controllable and easier to learn than the time-based method. Our work shows that a single depth camera can be used to combine locomotion and direction control in a simple and affordable setup.

Designing presence for real locomotion in immersive virtual environments: an affordance-based experiential approach

This paper describes a framework for designing systems for real locomotion in virtual environments (VEs) in order to achieve an intense sense of presence. The main outcome of the present research is a list of design features that the virtual reality technology should have in order to achieve such a goal. To identify these features, an approach based on the combination of two design strategies was followed. The first was based on the theory of affordances and was utilized to design a generic VE in which the affordances of the corresponding real environment could be evoked. The second was the experiential design applied to VEs and was utilized to create an experience of locomotion corresponding to that achievable in a real environment. These design strategies were chosen because of their potential to enhance the sense of presence. The proposed list of features can be utilized as an instrument that allows VE designers to evaluate the maturity of their systems and to pinpoint directions for future developments. A survey analysis was performed using the proposed framework, which involved three case studies to determine how many features of the proposed framework were present and their status. The result of such analysis represented a measure of the completeness of the systems design, of the affordances provided to the user, and a prediction of the sense of presence.

Personified and Multistate Camera Motions for First-Person Navigation in Desktop Virtual Reality

In this paper we introduce novel 'Camera Motions' (CMs) to improve the sensations related to locomotion in virtual environments (VE). Traditional Camera Motions are artificial oscillating motions applied to the subjective viewpoint when walking in the VE, and they are meant to evoke and reproduce the visual flow generated during a human walk. Our novel camera motions are: (1) multistate, (2) personified, and (3) they can take into account the topography of the virtual terrain. Being multistate, our CMs can account for different states of locomotion in VE namely: walking, but also running and sprinting. Being personified, our CMs can be adapted to avatar's physiology such as to its size, weight or training status. They can then take into account avatar's fatigue and recuperation for updating visual CMs accordingly. Last, our approach is adapted to the topography of the VE. Running over a strong positive slope would rapidly decrease the advance speed of the avatar, increase its energy loss, and eventually change the locomotion mode, influencing the visual feedback of the camera motions. Our new approach relies on a locomotion simulator partially inspired by human physiology and implemented for a real-time use in Desktop VR. We have conducted a series of experiments to evaluate the perception of our new CMs by naive participants. Results notably show that participants could discriminate and perceive transitions between the different locomotion modes, by relying exclusively on our CMs. They could also perceive some properties of the avatar being used and, overall, very well appreciated the new CMs techniques. Taken together, our results suggest that our new CMs could be introduced in Desktop VR applications involving first-person navigation, in order to enhance sensations of walking, running, and sprinting, with potentially different avatars and over uneven terrains, such as for: training, virtual visits or video games.

A feedback-controlled interface for treadmill locomotion in virtual environments

Virtual environments (VEs) allow safe, repeatable, and controlled evaluations of obstacle avoidance and navigation performance of people with visual impairments using visual aids. Proper simulation of mobility in a VE requires an interface, which allows subjects to set their walking pace. Using conventional treadmills, the subject can change their walking speed by pushing the tread with their feet, while leveraging handrails or ropes (self-propelled mode). We developed a feedback-controlled locomotion interface that allows the VE workstation to control the speed of the treadmill, based on the position of the user. The position and speed information is also used to implement automated safety measures, so that the treadmill can be halted in case of erratic behavior. We compared the feedback-controlled mode to the self-propelled mode by using speed-matching tasks (follow a moving object or match the speed of an independently moving scene) to measure the efficacy of each mode in maintaining constant subject position, subject control of the treadmill, and subject pulse rates. Additionally, we measured the perception of speed in the VE on each mode. The feedback-controlled mode required less physical exertion than self-propelled. The average position of subjects on the feedback-controlled treadmill was always within a centimeter of the desired position. There was a smaller standard deviation in subject position when using the self-propelled mode than when using the feedback-controlled mode, but the difference averaged less than six centimeters across all subjects walking at a constant speed. Although all subjects underestimated the speed of an independently moving scene at higher speeds, their estimates were more accurate when using the feedback-controlled treadmill than the self-propelled.

The Perception of Walking Speed in a Virtual Environment

Studies of locomotion in virtual environments assume that correct geometric principles define the relationship between walking speed and environmental flow. However, we have observed that geometrically correct optic flow appears to be too slow during simulated locomotion on a treadmill. Experiment 1 documents the effect in a head-mounted display. Experiment 2 shows that the effect is eliminated when the gaze is directed downward or to the side, or when the walking speed is slow. Experiment 3 shows that the effect is unchanged by stride length. Experiment 4 verifies that the effect is not attributable to image jitter. The change in perceived speed from straight ahead to side or down gaze coincides with a shift from expanding optic flow to lamellar flow. Therefore, we hypothesize that lamellar flow is necessary for accurate speed perception, and that a limited field of view eliminates this cue during straight-ahead gaze.

지면의 미끄러운 정도에 따른 캐릭터의 걷기 동작 생성

3차원 가상현실 내에서 캐릭터 움직임 동작의 기술은 기존 방식인 키프레임 기법에 의존하던 것이 점차 동작 제어 기법을 활용하고, 보다 사실적이고 자연스러운 움직임을 생성해 내고자 하는 방향으로 발전해 가고 있다. 그러나 이러한 동작 제어 기법을 통해 가상현실의 지형 성질에 따라 적응적인 캐릭터의 동작을 표현하는데 한계가 있다. 즉, 대부분의 가상환경에서 캐릭터의 걷는 움직임은 일정하고 단조로운 동작만을 반복하여 표현하고 있어 관찰자로 하여금 지루함을 느끼게 하고, 지형의 조건이나 형태에 맞지않게 캐릭터의 발끝이 지면에 스며들거나 떠있는 등의 부자연스러운 동작으로 인해 사실감을 저하시킨다. 본 논문에서는 적은 매개변수들과 역운동학 방법을 적용하여 기본 걷기 동작을 표현하고, 지면의 성질을 마찰계수로 대표시켜 지면에 적응적인 걷기 동작의 생성 방법을 제안한다. 제안된 방법에서는 구심력과 마찰계수를 결합한 후, 이를 근거로하여 한 주기 동안의 걷는 동작을 분석하고 이를 기반으로 동작에 필요한 매개변수를 조정하여 지질에 따른 적응적인 캐릭터의 걷기 동작을 생성한다. In 3D virtual environment the description of character' s movement that has utilized the conventional key-frame technique is gradually being developed toward the application of motion control method to generate more realistic and natural motion. Even the motion control method, however, has the limitation for expression of character's motion adapted to the ground properties of virtual world. That is, the walking motions of character are not only, for the most part, so uniform simple and repeated often as to feel to be tedious, but also the unnatural motion in which the tips of the toes soak through a plane or float in the air discording with the conditions of terrain lowers the semblance of reality. This paper proposes an adaptive motion control method for human figure locomotion in virtual environments or games, in which the walking motion is dynamiccally adapted to the ground's sliding properties. We compute an optimal parameters for one cycle of walking motion adapted to the ground properties by combining the coefficient of friction and centripetal force, and therefrom we induce a set of nonskid speed corresponding to various sliding properties of the ground.

Human Action Laws in Electronic Virtual Worlds: An Empirical Study of Path Steering Performance in VR

This paper is concerned with simple human performance “laws of action” for three classes of tasks—pointing, crossing, and steering, as well as their applications in Virtual Reality research. In comparison to Fitts' law of pointing, the “law of steering”— the quantitative relationship between human temporal performance and the movement path's spatial characteristics—has been notably under investigated. After a review of research on the law of steering in different domains and time periods, we examine the applicability of the law of steering in a VR locomotion task. Participants drove a virtual vehicle in a virtual environment on paths whose shape and width were systematically manipulated. Results showed that the law of steering indeed applies to locomotion in Virtual Environments. Participants' mean trial completion times linearly correlated (r2 between 0.985 and 0.999) with an index of difficulty quantified as path length to width ratio for the straight and circular paths used in this experiment. On average both the mean and the maximum speeds of the participants were linearly proportional to path width. Such human performance regularity provides a quantitative tool for 3D human-machine interface design and evaluation. We also propose to use the law-of-steering model in Virtual Reality manipulation tasks such as the “ring and wire” task in the future.

The Torus Treadmill: realizing locomotion in VEs

Locomotion in virtual environments (VEs) remains one of the major problems in current virtual reality research. The most intuitive way to move about the real world is to travel on foot. People often feel a better sense of distance or direction while walking than while riding in a vehicle. This article discusses the development of a locomotion device that provides a sense of walking. In terms of natural interaction, the physical exertion of walking proves essential to locomotion. The research of my colleagues and I aims to give users a sense of walking while their position remains localized in the physical world. We've developed several prototypes of interface devices for walking. From the results of our research, we concluded that an infinite surface would offer an ideal means for giving people a sense of walking. Our device, called the Torus Treadmill, uses a torus-shaped surface to realize the locomotion interface. The surface employs 12 sets of treadmills connected side-by-side and driven in a perpendicular direction. These treadmills generate an infinite surface. We measured the motion of the users' feet with magnetic sensors. The floor moves in the opposite direction of the walker, canceling the motion of each step. The walker's position remains localized in the real world by this computer-controlled motion of the floor. The walker can freely change direction. An image of the virtual space appears in a head-mounted display corresponding to the walker's virtual position.

Locomotion in a Virtual Environment: Performance Measures and Physiological Responses

We are developing and studying a human-computer interface that allows a scientist to interact with complex software systems through immersive virtual reality technology. Virtual tools are being developed to empower the user to view, manipulate, model, diagnose, analyze, navigate through the software simulations and the multidimensional data it generates. For these tools to be truly effective, they must be evaluated in the context of human performance studies. This paper addresses one such category of tool: an efficient and natural means of locomotion in 3D virtual spaces. The current study is investigating three different methods of virtual body locomotion in the following context. Subjects were required to fly through a series of 3D tunnels while performance times and number of wall collisions were used as response measures. In addition, during each trial subjects were continuously monitored for physiological responses and psychological assessments were performed before and after the series of flights. This paper reports on the preliminary findings of the current study and the lessons learned in performing empirical studies on locomotion in virtual environments.

The Effects of Optic Flow, Proprioception, and Texture on Novice Locomotion in Virtual Environments

The ability of a user to move to different locations within a virtual environment (VE) is a fundamental action that subserves the activities of exploration and manipulation. By empirical analogy, the perceptual information used to locomote to a target within a virtual environment is compared to the perceptual information used to walk to a location in the real world. An experiment is reported that had participants move to a location as accurately as possible within a VE where a target object was presented. The amount of visual feedback available to participants was manipulated. Three conditions were compared: static viewing of the target and virtual environment before locomotion, the disappearance of the target object as movement to the object was initiated, and locomotion to the target while both object and environment were present. In addition, the composition of virtual environments was either textured or polygonal. Error measures indicated that users locomote within VE's with less accuracy than those that walk blindfolded in the real world. Texture had its largest effect on the accuracy of movement when optic flow was not available, that is, static estimates of distance. Discussions center on the relative contribution of visual, cognitive, and proprioceptive information to VE user movement accuracy.