Walking In Virtual Environment Research Articles

Transferable Virtual-Physical Environmental Alignment With Redirected Walking.

Several advanced redirected walking techniques have been proposed in recent years to improve natural walking in virtual environments. One active and important research challenge of redirected walking focuses on the alignment of virtual and physical environments by redirection gains. If both environments are aligned, physical objects appear at the same positions as their virtual counterparts. When a user arrives at such a virtual object, she can touch the corresponding physical object providing passive haptic feedback. When multiple transferable virtual or physical target positions exist, the alignment can exploit multiple options, but the process requires more complicated solutions. In this paper, we study the problem of virtual-physical environmental alignment at multiple transferable target positions, and introduce a novel reinforcement learning-based redirected walking method. We design a novel comprehensive reward function that dynamically determines virtual-physical target matching and updates virtual target weights for reward computation. We evaluate our method through various simulated experiments as well as real user tests. The results show that our method obtains less physical distance error for environmental alignment and requires fewer resets than state-of-the-art techniques.

Comparison of sagittal plane gait characteristics between the overground and treadmill approach for gait analysis in typically developing children.

BackgroundInstrumented treadmills have become more mainstream in clinical assessment of gait disorders in children, and are increasingly being applied as an alternative to overground gait analysis. Both approaches differ in multiple elements of set-up (e.g., overground versus treadmill, Pug-in Gait versus Human Body Model-II), workflow (e.g., limited amount of steps versus many successive steps) and post-processing of data (e.g., different filter techniques). These individual elements have shown to affect gait. Since the approaches are used in parallel in clinical practice, insight into the compound effect of the multiple different elements on gait is essential. This study investigates whether the outcomes of two approaches for 3D gait analysis are interchangeable in typically developing children.MethodsSpatiotemporal parameters, sagittal joint angles and moments, and ground reaction forces were measured in typically developing children aged 3–17 years using the overground (overground walking, conventional lab environment, Plug-In Gait) and treadmill (treadmill walking in virtual environment, Human Body Model-II) approach. Spatiotemporal and coefficient of variation parameters, and peak values in kinematics and kinetics of both approaches were compared using repeated measures tests. Kinematic and kinetic waveforms from both approaches were compared using statistical parametric mapping (SPM). Differences were quantified by mean differences and root mean square differences.ResultsChildren walked slower, with lower stride and stance time and shorter and wider steps with the treadmill approach than with the overground approach. Mean differences ranged from 0.02 s for stride time to 3.3 cm for step width. The patterns of sagittal kinematic and kinetic waveforms were equivalent for both approaches, but significant differences were found in amplitude. Overall, the peak joint angles were larger during the treadmill approach, showing mean differences ranging from 0.84° (pelvic tilt) to 6.42° (peak knee flexion during swing). Mean difference in peak moments ranged from 0.02 Nm/kg (peak knee extension moment) to 0.32 Nm/kg (peak hip extension moment), showing overall decreased joint moments with the treadmill approach. Normalised ground reaction forces showed mean differences ranging from 0.001 to 0.024.ConclusionThe overground and treadmill approach to 3D gait analysis yield different sagittal gait characteristics. The systematic differences can be due to important changes in the neuromechanics of gait and to methodological choices used in both approaches, such as the biomechanical model or the walkway versus treadmill. The overview of small differences presented in this study is essential to correctly interpret the results and needs to be taken into account when data is interchanged between approaches. Together with the research/clinical question and the context of the child, the insight gained can be used to determine the best approach.

The Role of Binocular Vision in Avoiding Virtual Obstacles While Walking.

Advances in Virtual Reality technology have enabled physical walking in virtual environments. While most Virtual Reality systems render stereoscopic images to users, the implication of binocular viewing with respect to the performance of human walking in virtual environments remains largely unknown. In the present study, we conducted two walking experiments in virtual environments using a linear treadmill and a novel projected display known as the Wide Immersive Stereo Environment (WISE) to study the role of binocular viewing in virtual locomotion. The first experiment investigated the walking performance of people stepping over obstacles while the second experiment focused on a scenario on stepping over gaps. Both experiments were conducted under both stereoscopic viewing and non-stereoscopic viewing conditions. By analysing the gait parameters, we found that binocular viewing helped people to make more accurate movements to step over obstacles and gaps in virtual locomotion.

Optimal Frequency and Amplitude of Vertical Viewpoint Oscillation for Improving Vection Strength and Reducing Neural Constrains on Gait.

Inducing self-motion illusions referred as vection are critical for improving the sensation of walking in virtual environments (VE). Adding viewpoint oscillations to a constant forward velocity in VE is effective for improving vection strength under static conditions. However, the effects of oscillation frequency and amplitude on vection strength under treadmill walking conditions are still unclear. Besides, due to the visuomotor entrainment mechanism, these visual oscillations would affect gait patterns and be detrimental for achieving natural walking if not properly designed. This study was aimed at determining the optimal frequency and amplitude of vertical viewpoint oscillations for improving vection strength and reducing gait constraints. Seven subjects walked on a treadmill while watching a visual scene. The visual scene presented a constant forward velocity equal to the treadmill velocity with different vertical viewpoint oscillations added. Five oscillation patterns with different combinations of frequency and amplitude were tested. Subjects gave verbal ratings of vection strength. The mediolateral (M-L) center of pressure (CoP) complexity was calculated to indicate gait constraints. After the experiment, subjects were asked to give the best and the worst oscillation pattern based on their walking experience. The oscillation frequency and amplitude had strong positive correlations with vection strength. The M-L CoP complexity was reduced under oscillations with low frequency. The medium oscillation amplitude had greater M-L CoP complexity than the small and large amplitude. Besides, subjects preferred those oscillation patterns with large gait complexity. We suggested that the oscillation amplitude with largest M-L CoP complexity should first be chosen to reduce gait constraints. Then, increasing the oscillation frequency to improve vection strength until individual preference or the boundary of motion sickness. These findings provide important guidelines to promote the sensation of natural walking in VE.

Development of a speed protector to optimize user experience in 3D virtual environments

Virtual walking in virtual environments (VEs) requires locomotion interfaces, especially when the available physical environment is smaller than the virtual space due to virtual reality facilities limitations; many navigation approaches have been proposed according to different input conditions, target selection and speed selection. With current technologies, the virtual locomotion speed for most VR systems relies primarily on rate-control devices (e.g., joystick). The user has to manage manual adaptation of the speed, based on the size of the VE and personal preferences. However, this method cannot provide optimal speeds for locomotion as the user tends to change the speed involuntarily due to non-desired issues including collisions or simulator sickness; in this case, the user may have to adjust the speed frequently and unsmoothly, worsening the situation. Therefore, we designed a motion protector that can be embedded into the locomotion system to provide optimal speed profiles. The optimization process aims at minimizing the total jerk when the user translates from an initial position to a target, which is a common rule of the human motion model. In addition to minimization, we put constraints on speed, acceleration and jerk so that they do not exceed specific thresholds. The speed protector is formulated mathematically and solved analytically in order to provide a smooth navigation experience with a minimum jerk of trajectory. The assessment of the speed protector was conducted in a user study measuring user experience with a simulator sickness questionnaire, event-related skin conductance responses (ER-SCR), and a NASA-TLX questionnaire, showing that the designed speed protector can provide more natural and comfortable user experience with appropriate acceleration and jerk as it avoids abrupt speed profiles.

Nurses' Participation in the Design of an Intensive Care Unit: The Use of Virtual Mock-Ups.

Co-design with multiple tools is useful when end users' knowledge is important, especially when designers work with people unfamiliar with design. Many studies have highlighted the importance of nurses' participation in design, and such participation requires the development of techniques and tools to facilitate collaboration. This article analyzes how nurses participated in designing a general intensive care unit in a walk-in virtual environment (VE) and examines how their work-related knowledge can be transferred to the design process of spaces. In this action research study, the design process was conducted by using virtual mock-ups, which were evaluated by multi-occupational groups in a walk-in VE. Nurses were the largest occupational group. Their work processes were under modification, since existing multi-patient rooms were being redesigned as single-patient rooms. The design of single-patient rooms was performed in three iterative cycles in the walk-in VE. The nurses could specify their requirements in the walk-in VE, and their suggestions were incorporated into the architectural design process. The nurses were satisfied with their role in the design process. Co-design with virtual mock-ups in walk-in VE is appropriate when designing new healthcare facilities and when the opinions of workers are important. Virtual mock-ups in walk-in VE can be used collaboratively, facilitating simultaneous feedback from multiple users. Virtual reality (VR) technology has evolved, and changes can be made rapidly and at a lower cost. Another advantage of VR is that it allows one to design larger spaces, thus providing larger layouts of facilities for evaluation.

Use of Virtual Environment and Virtual Prototypes in Co-Design: The Case of Hospital Design

Co-design is used for improving innovation, obtaining better solutions, and higher user satisfaction. In this paper we present how the use of a walk-in virtual environment and actual-size virtual prototypes support co-design. Unlike in most studies we presented the prototypes to users in an early phase of the design process. This study examines the co-design of healthcare facilities with multi-occupational groups. The practical case examines designing single-patient rooms for an intensive care unit. In this design process 238 participants of different hospital professions evaluated virtual prototypes in three iterative rounds. The participants improved the design by discussing their work practices. The virtual environment situation and actual size virtual prototypes make an easy environment for users to discuss and evaluate the design without any design knowledge. In addition to describing the co-design results we also outline some important issues and guidelines about creating the virtual prototypes and organizing the participants’ visits in a virtual environment.

Analyses of Gait Parameters of Younger and Older Adults During (Non-)Isometric Virtual Walking.

Understanding real walking in virtual environments (VEs) is important for immersive experiences, allowing users to move through VEs in the most natural way. Previous studies have shown that basic implementations of real walking in virtual spaces, in which head-tracked movements are mapped isometrically to a VE, are not estimated as entirely natural. Instead, users estimate a virtual walking velocity as more natural when it is slightly increased compared to the user's physical locomotion. However, these findings have been reported in most cases only for young persons, e.g., students, whereas older adults are clearly underrepresented in such studies. Recently, virtual reality (VR) has received significant public and media attention. Therefore, it appears reasonable to assume that people at different ages will have access to VR, and might use this technology more and more in application scenarios such as rehabilitation or training. To better understand how people at different ages walk and perceive locomotion in VR, we have performed a study to investigate the effects of (non-)isometric mappings between physical movements and virtual motions in the VE on the walking biomechanics across generations, i.e., younger and older adults. Three primary domains (pace, base of support and phase) of spatio-temporal parameters were identified to evaluate gait performance. The results show that the older adults walked very similar in the real and VE in the pace and phasic domains, which differs from results found in younger adults. In contrast, the results indicate differences in terms of base of support domain parameters for both groups while walking within a VE and the real world. For non-isometric mappings, we found in both younger and older adults an increased divergence of gait parameters in all domains correlating with the up- or down-scaled velocity of visual self-motion feedback. The results provide important insights into the design of future VR applications for older adults in domains ranging from medicine and psychology to rehabilitation.

Walking in Virtual Reality

Walking constitutes the predominant form of self-propelled movement from one geographic location to another in our real world. Likewise, walking in virtual environments (VEs) is an essential part of a users experience in many application domains requiring a high degree of interactivity. However, researchers and practitioners often observe that basic implementations of virtual walking, in which head-tracked movements are mapped isometrically to a VE are not estimated as entirely natural. Instead, users estimate a virtual walking velocity as more natural when it is slightly increased compared to the users physical body movement. In this article, we investigate the effects of such nonisometric mappings between physical movements and virtual motions in the VE on walking velocity and biomechanics of the gait cycle. Therefore, we performed an experiment in which we measured and analyzed parameters of the biomechanics of walking under conditions with isometric as well as nonisometric mappings. Our results show significant differences in most gait parameters when walking in the VE in the isometric mapping condition compared to the corresponding parameters in the real world. For nonisometric mappings we found an increased divergence of gait parameters depending on the velocity of visual self-motion feedback. The results revealed a symmetrical effect of gait detriments for up- or down-scaled virtual velocities, which we discuss in the scope of the previous findings.

Real Walking in Virtual Environments for Factory Planning and Evaluation

Nowadays, buildings or production facilities are designed using specialized design software and building information modeling tools help to evaluate the resulting virtual mock-up. However, with current, primarily desktop based tools it is hard to evaluate human factors of such a design, for instance spatial constraints for workforces. This paper presents a new tool for factory planning and evaluation based on virtual reality that allows designers, planning experts, and workforces to walk naturally and freely within a virtual factory. Therefore, designs can be checked as if they were real before anything is built.

Evidence Against a Correlation Between Ease of Use and Actual Use of a Device in a Walk-in Virtual Environment

Technology acceptance and its use are assumed to be based on the perceived usefulness and ease of use of the technology. We studied one aspect of that by focusing on a possible correlation between the actual use of a device and its perceived ease of use. For studying technology that is new to users, we investigated the use of a locomotion control device in a walk-in virtual environment. We organized a user test in which participants browsed virtual shopping items by walking or by controlling locomotion with a device. Data were gathered in two ways: First, we observed their actual device use, and second, we asked users to evaluate the ease of use of the device. The analysis illustrates that there is no correlation between the actual use and ease of use of the device.

Impossible Spaces: Maximizing Natural Walking in Virtual Environments with Self-Overlapping Architecture

Walking is only possible within immersive virtual environments that fit inside the boundaries of the user's physical workspace. To reduce the severity of the restrictions imposed by limited physical area, we introduce "impossible spaces," a new design mechanic for virtual environments that wish to maximize the size of the virtual environment that can be explored with natural locomotion. Such environments make use of self-overlapping architectural layouts, effectively compressing comparatively large interior environments into smaller physical areas. We conducted two formal user studies to explore the perception and experience of impossible spaces. In the first experiment, we showed that reasonably small virtual rooms may overlap by as much as 56% before users begin to detect that they are in an impossible space, and that the larger virtual rooms that expanded to maximally fill our available 9.14 m x 9.14 m workspace may overlap by up to 31%. Our results also demonstrate that users perceive distances to objects in adjacent overlapping rooms as if the overall space was uncompressed, even at overlap levels that were overtly noticeable. In our second experiment, we combined several well-known redirection techniques to string together a chain of impossible spaces in an expansive outdoor scene. We then conducted an exploratory analysis of users' verbal feedback during exploration, which indicated that impossible spaces provide an even more powerful illusion when users are naive to the manipulation.

The future of the CAVE

AbstractThe CAVE, a walk-in virtual reality environment typically consisting of 4–6 3 m-by-3 m sides of a room made of rear-projected screens, was first conceived and built in 1991. In the nearly two decades since its conception, the supporting technology has improved so that current CAVEs are much brighter, at much higher resolution, and have dramatically improved graphics performance. However, rear-projection-based CAVEs typically must be housed in a 10 m-by-10 m-by-10 m room (allowing space behind the screen walls for the projectors), which limits their deployment to large spaces. The CAVE of the future will be made of tessellated panel displays, eliminating the projection distance, but the implementation of such displays is challenging. Early multi-tile, panel-based, virtual-reality displays have been designed, prototyped, and built for the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia by researchers at the University of California, San Diego, and the University of Illinois at Chicago. New means of image generation and control are considered key contributions to the future viability of the CAVE as a virtual-reality device.

The effect of HMD mass and inertia on visually directed walking in virtual environments

The effect of HMD mass and inertia on visually directed walking in virtual environments

Evaluation of Reorientation Techniques and Distractors for Walking in Large Virtual Environments

Virtual Environments (VEs) that use a real-walking locomotion interface have typically been restricted in size to the area of the tracked lab space. Techniques proposed to lift this size constraint, enabling real walking in VEs that are larger than the tracked lab space, all require reorientation techniques (ROTs) in the worst-case situation-when a user is close to walking out of the tracked space. We propose a new ROT using visual and audial distractors-objects in the VE that the user focuses on while the VE rotates-and compare our method to current ROTs through three user studies. ROTs using distractors were preferred and ranked more natural by users. Our findings also suggest that improving visual realism and adding sound increased a user's feeling of presence. Users were also less aware of the rotating VE when ROTs with distractors were used. Our findings also suggest that improving visual realism and adding sound increased a user's feeling of presence.

Development of a New Virtual Reality System

To implement the operator’s free walking in virtual environment (VE), a new configuration of virtual reality (VR) system is presented. In this system, a special machine is designed and it enables the operator to walk inside the VE in any directions over a long distance without actually leaving the physical device. Images produced by the computer are projected upon the surface of a large spherical screen surround the operator by means of a group of high power projectors. The new VR system can acquire wide view angle and form panorama surround the operator, which may enhance the realistic sense of the simulation. For some reasons, we only finished a part of the construction of this system at present and the key techniques involved are also discussed. As preliminary realization of this system, we built the key component – walking machine and carried out an experiment to verify its effectiveness.

A Novel Locomotion Interface with Two 6-DOF Parallel Manipulators That Allows Human Walking on Various Virtual Terrains

This paper proposes a novel locomotion interface that can generate an infinite floor with various surfaces and can provide a user with proprioceptive feedback about walking. The interface allows users to experience life-like walking in virtual environments with various terrains. The interface consists of two platforms, each consisting of a three-degrees-of-freedom (3-DOF; x, y and yaw) planar device on which a 3-DOF (pitch, roll and z) footpad is mounted. Alternating current servomotors drive the planar devices to generate rapid motions, while pneumatic actuators drive the footpad devices to generate the impedances required for various virtual terrains, in addition to supporting the user’s weight. To simulate natural human walking, the locomotion interface design specifications are based on gait analysis, and each mechanism is optimally designed and manufactured to satisfy these requirements. The locomotion interface allows natural walking (step, 0.8 m; height, 20 cm; load capability, 100 kg; slope, 55°) on various terrains. In addition, a new walking control algorithm is proposed for generating continuous walking on an infinite floor involving various terrains. In this algorithm, each independent platform follows a human foot during the swing phase, while the other platform returns to the home position during the single-limb stance phase. During the double-limb stance phase, the two platforms assume neutral positions to compensate for the offset errors generated by velocity changes. Therefore, this algorithm can satisfy natural walking conditions in any direction. The transition phase between the swing and stance phases is detected using a simple switch sensor system, while human foot motions are sensed using a calibrated magnetic motion tracker attached to the shoe. Actual walking simulations on level ground, slopes, and stairs show that the proposed locomotion interface allows an average person to walk naturally on various virtual terrains in safety, without marked disturbances. This interface has various applications, such as in virtual reality (VR) navigation, rehabilitation, and gait analysis.

Development of a New Virtual Environment System for Assembly

In order to make the operator freely walk in virtual environment (VE), a new prototype of VE system for assembly is presented in this paper. In this system, a special machine is designed and it enables the operator to walk inside the VE in any directions over a long distance without actually leaving the physical device. Images produced by the computer are projected upon the surface of a large spherical cap screen surrounding the operator by means of a group of high power projectors. Signals provided by the position sensors attached to the operator are used by the computer to update the projected images, which provides the operator the illusion of walking freely through the virtual scenes. This VE system can acquire wide field of view and form panorama surrounding the operator, which may enhance the realistic sense of simulation.