Where are you going? Using human locomotion models for target estimation

To explore virtual environments that are larger than the available physical tracking space by real walking, it is necessary to use so-called redirected walking. Redirection techniques allow the user to explore an unlimited virtual environment in a limited tracking space by introducing a small mismatch between a user’s real and virtual movement, thus preventing the user from colliding with the physical walls of the tracking space. Steering algorithms are used to select the most suitable redirection technique at any given time, depending on the geometry of the real and virtual environment. Together with prediction of a user’s future walking path, these algorithms select the best redirection strategy by an optimal control scheme. In this paper, a new approach for the prediction of a person’s locomotion target is presented. We use various models of human locomotion together with a set of possible targets to create a set of expected paths. These paths are then compared to the real path the user already traveled to calculate the probability of a certain target being the one the user is heading for. A new approach for comparing paths with each other is introduced and is compared to three others. For describing the human’s path to a given target, four different models are used and compared. To gather data for the comparison of the models against the real path, a user study was conducted. Based on the results of the user study, the paper concludes with a discussion on the prediction performance of the different approaches.     

Study on interaction-induced symptoms with respect to virtual grasping and manipulation

Owing to the popularity of various hand tracking interfaces, there have been numerous applications developed to provide intuitive hand interaction with the virtual world. As users start with great anticipation, they end up with dissatisfaction due to difficulties of manipulation or physical tiredness coming very short. Although the task itself is rather trivial in a real life situation, it requires much effort in the virtual environment. We address this awkwardness as ‘VR interaction-induced fatigue symptom’ and hypothesize its causes based on our observations. We argue that the source of the fatigue comes from the restricted sensory information of the VR interfaces, and that users try to accommodate the missing sensory feedback by excessive motion leading to wrong posture or bad timing. We demonstrate our hypothesis by conducting experiments of two types of virtual interaction scenarios: object transport and 3D selection. Furthermore, by analyzing the behaviors of users' action collected from our experiment, we derive essential factors to be considered in designing VR applications, and propose a conceptual interaction model for orchestrating virtual grasping.     

An Image-Based Virtual Reality Prototype System

The most important goal of virtual reality is to create a virtual world computers where users are allowed to view the environment and control the virtual objects interactively.Traditionally,virtual reality systems use 3D computer graphics to model and render a virtual environment in real time.However,this approach usually requires laborious modeling and expensive special-purpose rendering hardware.Image-based rendering is a new approach in composing a virtual environment in which a set of panoramic images is used to compose the virtual environment and walking in the space is accomplished by “hopping”to different panoramic points.This paper introduces an experimental image-based VR system.The techniques utilized in the system,in particular the authoring and interactive control tools of the system,are described in detail.     

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     

User-centered redirected walking and resetting with virtual feelers

Virtual Reality - With redirected walking (RDW), the exploration of an infinite virtual world with a small physical space has been enabled. This paper proposes a user-centered RDW (UC-RDW) and...     

RoleVR: Multi-experience in immersive virtual reality between co-located HMD and non-HMD users

In this study, we present RoleVR, which can provide a similar high level of presence and multi experience for co-located head-mounted display (HMD) and Non-HMD users in an asymmetric virtual reality (VR) environment. The core of RoleVR is distinguishing the difference between the asymmetric environments (in terms of the system and the experience) of HMD and Non-HMD users to design optimized roles for these users. Here, we assign HMD user with spatial role that maximizes the sense of space based on three-dimensional visual information, and we assign Non-HMD user with temporal role in which they take control of communication and action, and understand the overall situation according to the flow of time. We also design an interaction for walking and a hand interface to enhance presence. This is achieved by understanding the user’s role, thereby improving the immersion. Finally, we created an asymmetric VR application that considers the interaction between roles and performed survey-based experiments to verify the basic presence and multi-experience of users in RoleVR. Through this process, we confirmed that RoleVR provides satisfactory presence for co-located HMD and Non-HMD users, and a variety of experiences specialized for each role.

     

Redirecting walking and driving for natural navigation in immersive virtual environments

Walking is the most natural form of locomotion for humans, and real walking interfaces have demonstrated their benefits for several navigation tasks. With recently proposed redirection techniques it becomes possible to overcome space limitations as imposed by tracking sensors or laboratory setups, and, theoretically, it is now possible to walk through arbitrarily large virtual environments. However, walking as sole locomotion technique has drawbacks, in particular, for long distances, such that even in the real world we tend to support walking with passive or active transportation for longer-distance travel. In this article we show that concepts from the field of redirected walking can be applied to movements with transportation devices. We conducted psychophysical experiments to determine perceptual detection thresholds for redirected driving, and set these in relation to results from redirected walking. We show that redirected walking-and-driving approaches can easily be realized in immersive virtual reality laboratories, e. g., with electric wheelchairs, and show that such systems can combine advantages of real walking in confined spaces with benefits of using vehicle-based self-motion for longer-distance travel.     

Vision‐tangible interactive display method for mixed and virtual reality: Toward the human‐centered editable reality

Building a human‐centered editable world can be fully realized in a virtual environment. Both mixed reality (MR) and virtual reality (VR) are feasible solutions to support the attribute of edition. Based on the current development of MR and VR, we present the vision‐tangible interactive display method and its implementation in both MR and VR. We address the issue of MR and VR together because they are similar regarding the proposed method. The editable mixed and virtual reality system is useful for studies, which exploit it as a platform. In this paper, we construct a virtual reality environment based on the Oculus Rift, and an MR system based on a binocular optical see‐through head‐mounted display. In the MR system about manipulating the Rubik's cube, and the VR system about deforming the virtual objects, the proposed vision‐tangible interactive display method is utilized to provide users with a more immersive environment. Experimental results indicate that the vision‐tangible interactive display method can improve the user experience and can be a promising way to make the virtual environment better.     

The utility of a virtual reality locomotion interface for studying gait behavior

OBJECTIVE: To investigate the effect of optic flow on gait behavior during treadmill walking using an immersive virtual reality (VR) setup and compare it with conventional treadmill walking (TW) and overground walking (OW). BACKGROUND: Previous research comparing TW with OW speculated that a lack of optic flow (relative visual movement between a walker and the environment) during TW may have led to perceptual cue conflicts, resulting in differences in gait behavior, as compared with OW. METHOD: Participants walked under three locomotion conditions (OW, TW, and TW with VR [TWVR]) under three walking constraint conditions (no constraint, a temporal/pacing constraint, and a spatial/path-following constraint). Presence questionnaires (PQs) were administered at the close of the TWVR trials. Trials were subjected to video analysis to determine spatiotemporal and kinematics variables used for comparison of locomotion conditions. RESULTS: ANOVA revealed gait behavior during TWVR to be between that of OW and TW. Speed and cadence during TWVR were significantly different from those of TW, whereas knee angle was comparable to that of OW. Correlation analysis of PQ scores with gait measures revealed a positive linear association of the distraction subfactor of the PQ with walking speed during TWVR, suggesting an increase in the sense of presence in the virtual environment led to increases in walking speed. CONCLUSION: The results demonstrate that providing optic flow during TW through VR has an impact on gait behavior. APPLICATION: This study provides a basis for developing simple VR locomotion interface setups for gait research.     

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.     

Exploiting perceptual limitations and illusions to support walking through virtual environments in confined physical spaces

Head-mounted displays (HMDs) allow users to immerse in a virtual environment (VE) in which the user’s viewpoint can be changed according to the tracked movements in real space. Because the size of the virtual world often differs from the size of the tracked lab space, a straightforward implementation of omni-directional and unlimited walking is not generally possible. In this article we review and discuss a set of techniques that use known perceptual limitations and illusions to support seemingly natural walking through a large virtual environment in a confined lab space. The concept behind these techniques is called redirected walking. With redirected walking, users are guided unnoticeably on a physical path that differs from the path the user perceives in the virtual world by manipulating the transformations from real to virtual movements. For example, virtually rotating the view in the HMD to one side with every step causes the user to unknowingly compensate by walking a circular arc in the opposite direction, while having the illusion of walking on a straight trajectory. We describe a number of perceptual illusions that exploit perceptual limitations of motion detectors to manipulate the user’s perception of the speed and direction of his motion. We describe how gains of locomotor speed, rotation, and curvature can gradually alter the physical trajectory without the users observing any discrepancy, and discuss studies that investigated perceptual thresholds for these manipulations. We discuss the potential of self-motion illusions to shift or widen the applicable ranges for gain manipulations and to compensate for over- or underestimations of speed or travel distance in VEs. Finally, we identify a number of key issues for future research on this topic.     

虚拟现实大空间下多虚拟目标被动触觉交互方法

针对虚拟现实（VR）大空间下为重定向行走的用户提供被动触觉时存在的虚实交互目标无法一一对应的问题,提出了一种用两个物理代理作为触觉代理为多个虚拟目标提供触觉反馈的方法,以在基于人工势场（APF）的重定向行走过程中,交替地满足用户被动触觉的需求。针对重定向行走算法本身以及标定不精确等原因造成的虚实不对齐的问题,对虚拟目标的位置及朝向进行设计并且在交互阶段引入触觉重定向。仿真实验表明对虚拟目标位置和朝向的设计可以大幅降低对齐误差;而用户实验结果证明触觉重定向的引入进一步提升了交互准确性,且能为用户带来更丰富、更具沉浸感的体验。     

Estimation of Detection Thresholds for Redirected Walking Techniques

In immersive virtual environments (IVEs), users can control their virtual viewpoint by moving their tracked head and walking through the real world. Usually, movements in the real world are mapped one-to-one to virtual camera motions. With redirection techniques, the virtual camera is manipulated by applying gains to user motion so that the virtual world moves differently than the real world. Thus, users can walk through large-scale IVEs while physically remaining in a reasonably small workspace. In psychophysical experiments with a two-alternative forced-choice task, we have quantified how much humans can unknowingly be redirected on physical paths that are different from the visually perceived paths. We tested 12 subjects in three different experiments: (E1) discrimination between virtual and physical rotations, (E2) discrimination between virtual and physical straightforward movements, and (E3) discrimination of path curvature. In experiment E1, subjects performed rotations with different gains, and then had to choose whether the visually perceived rotation was smaller or greater than the physical rotation. In experiment E2, subjects chose whether the physical walk was shorter or longer than the visually perceived scaled travel distance. In experiment E3, subjects estimate the path curvature when walking a curved path in the real world while the visual display shows a straight path in the virtual world. Our results show that users can be turned physically about 49 percent more or 20 percent less than the perceived virtual rotation, distances can be downscaled by 14 percent and upscaled by 26 percent, and users can be redirected on a circular arc with a radius greater than 22 m while they believe that they are walking straight.     

A Virtual Reality Interface for Space Planning Tasks

Manipulating and assembling elements in a 3D space is a task which interests a huge number of potential applications whether they deal with real or abstract objects. Direct manipulation techniques in traditional interactive systems use 2D devices and do not allow an easy manipulation of 3D objects. To facilitate user interaction, we have studied direct manipulation techniques in a virtual reality environment. A VR interface is naturally object-oriented and allows the definition of real-world metaphors. Operators can thus work in the virtual world in a similar way to the real world: they perceive the position of objects through the depth cue of stereo view, and can grab and push them in any direction by means of avirtual handuntil they reach their destination. They can put an object on top of another and line it up with other objects. We model the virtual world as ajob-orientedworld which is governed by a few simple rules which facilitate object positioning. In this paper, we describe the design and implementation strategies to obtain a real-time performance on a low-level workstation.     

Evaluation of direct manipulation using finger tracking for complex tasks in an immersive cube

A solution for interaction using finger tracking in a cubic immersive virtual reality system (or immersive cube) is presented. Rather than using a traditional wand device, users can manipulate objects with fingers of both hands in a close-to-natural manner for moderately complex, general purpose tasks. Our solution couples finger tracking with a real-time physics engine, combined with a heuristic approach for hand manipulation, which is robust to tracker noise and simulation instabilities. A first study has been performed to evaluate our interface, with tasks involving complex manipulations, such as balancing objects while walking in the cube. The user’s finger-tracked manipulation was compared to manipulation with a 6 degree-of-freedom wand (or flystick), as well as with carrying out the same task in the real world. Users were also asked to perform a free task, allowing us to observe their perceived level of presence in the scene. Our results show that our approach provides a feasible interface for immersive cube environments and is perceived by users as being closer to the real experience compared to the wand. However, the wand outperforms direct manipulation in terms of speed and precision. We conclude with a discussion of the results and implications for further research.     

关于在VRML技术中应用STK模型的研究

虚拟现实(Virtual Reality，简称VR)是一种可以创建和体验虚拟世界的计算机系统。VRML(Virtual Reality Modeling Language)为虚拟世界的建立提供了规范，VRML在电子商务、教育、工程技术、建筑、娱乐、艺术等领域的广泛应用。将会成为构建虚拟现实应用系统的基础。由于VRML与网络紧密联系，可以利用VRML技术将航天任务模拟从单机转移到冈上，这样网络用户就可以从互联网上了解航天任务的进行。但是模型的建立是非常困难和繁琐的。利用美国AGI(Analytical Graphics。Inc．)公司开发的STK(Satellite Tool Kit)就可以获得关于描绘空间飞行器、飞机、地面车辆、地面站、目标等资源丰富的模型。该文分别介绍了STK和VRML模型文件的特点，通过对两种模型文件的分析。得出如何将STK模型文件转换成为VRML模型文件的具体方法，以便在虚拟世界中应用。     

一个沉浸式场景漫游系统的构建

虚拟现实技术,是一种可以创建和体验虚拟环境的计算机系统技术,在军事、游戏、室内设计等诸多领域都有着广泛的应用。一个沉浸式的虚拟现实系统,可以让用户完全沉浸在虚拟世界中,得到与真实世界近似相同的感受。在高精度定位跟踪系统的辅助下,利用visual studio开发环境和3ds max、virtools软件构建了一个沉浸式场景漫游系统,并给出了一个游戏应用示例和一个室内设计应用示例。     

VR interactive dialog system with verbal and nonverbal communication

We have constructed a dialog environment between a human and a virtual agent. With commercial off-the-shelf VR technologies, special devices such as a data glove have to be used for the interaction, but it is difficult for anyone to manipulate objects on their own. If there is a helper who has direct access to objects in virtual space, we may ask them. The question, however, is how to communicate with the helper. The basic idea is to utilize speech and gesture recognition systems. We have already reported the above-mentioned result, although only the avatar can move a virtual object in the current system. The user cannot freely manipulate virtual objects. Therefore, in a new attempt, we constructed a communication channel between virtual space and the real world so that the virtual object could be manipulated. In order to develop the new system, we extended the existing system to an internet meeting system allowing users in different places to interact with each other by voice and by a pointing action with a finger. This work was presented in part and awarded as Young Author Award at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

How virtual reality affects perceived learning effectiveness: a task–technology fit perspective

The application of virtual reality (VR) in improving users’ learning outcomes, especially in perceived learning effectiveness, is a new area. VR provides visualisation and interaction within a virtual world that closely resembles a real world, bringing an immersive study experience. It also has two special features: representational fidelity and immediacy of control. However, only when the technology fits the tasks that users are performing will it be adopted. In addition, technology itself cannot improve learning outcomes; certain learning behaviours, such as reflective thinking, should be prompted first so that learning outcomes can be improved. The research hypotheses derived from this model have empirically been validated using the responses to a survey among 180 users. These responses have been examined through SmartPLS 2.0. Surprisingly, task–technology fit does not moderate the relationship between VR and technology quality and the relationship between VR and technology accessibility. From this study, we can conclude that VR will influence reflective thinking and further indirectly improve perceived learning effectiveness.     

虚拟人行走的动作融合

研究在行走时虚拟人动作与虚拟地形之间的交互性。通过碰撞检测来确定人体在地面之上的正确位置。利用动作融合的方法,即将几个典型动作按合适的权重结合产生新的动作数据,实时地驱动虚拟人并使之对环境变化的反应满足视觉上的逼真性。融合过程中各原始动作的权重取决于沿着和垂直于人体运动方向的2个地面坡度,同时也通过对地形的几何分析来实现虚拟人对其周边地形的感知。