Natural perspective projections for head-mounted displays

The display units integrated in today's head-mounted displays (HMDs) provide only a limited field of view (FOV) to the virtual world. In order to present an undistorted view to the virtual environment (VE), the perspective projection used to render the VE has to be adjusted to the limitations caused by the HMD characteristics. In particular, the geometric field of view (GFOV), which defines the virtual aperture angle used for rendering of the 3D scene, is set up according to the display field of view (DFOV). A discrepancy between these two fields of view distorts the geometry of the VE in a way that either minifies or magnifies the imagery displayed to the user. It has been shown that this distortion has the potential to affect a user's perception of the virtual space, sense of presence, and performance on visual search tasks. In this paper, we analyze the user's perception of a VE displayed in a HMD, which is rendered with different GFOVs. We introduce a psychophysical calibration method to determine the HMD's actual field of view, which may vary from the nominal values specified by the manufacturer. Furthermore, we conducted two experiments to identify perspective projections for HMDs, which are identified as natural by subjects--even if these perspectives deviate from the perspectives that are inherently defined by the DFOV. In the first experiment, subjects had to adjust the GFOV for a rendered virtual laboratory such that their perception of the virtual replica matched the perception of the real laboratory, which they saw before the virtual one. In the second experiment, we displayed the same virtual laboratory, but restricted the viewing condition in the real world to simulate the limited viewing condition in a HMD environment. We found that subjects evaluate a GFOV as natural when it is larger than the actual DFOV of the HMD--in some cases up to 50 percent--even when subjects viewed the real space with a limited field of view.     

Measurement of presence and its consequences in virtual environments

A sense of presence is one of the critical components required by any effective virtual environment (VE). In contrast, side effects such as sickness may be produced in some virtual environments, detracting from the enjoyment or usefulness of the VE and from subsequent performance of the participant. Both presence and sickness in virtual environments are multifactorial phenomena not easily amenable to understanding or measurement. The first experiment reported here compares use of direct performance measures and rating scales to assess presence, whilst varying the VE display medium (head mounted and desktop displays) and whether or not sound was used in the VE. The second experiment addresses associations between presence, sickness and enjoyment of virtual environment participation. There was enough comparability between a reflex response within the VE and the rating scales to justify future exploration of the former measure of presence. A number of explanations are given for the partial association found between presence and sickness.     

Intelligent Cruise-Control Navigation: A new navigation/travel method for use in virtual environments

An important feature of virtual reality is the facility for the user to move around a virtual environment in a natural and easily controlled manner. Navigation, also called locomotion, travel or motion, involves changing the perspective of the user in the virtual environment (VE). It allows the user to move in the VE as well as reorient themselves to look at the world differently. Natural locomotion methods are able to contribute to a sense of presence and reality. The illusion of presence can be lost through unnatural experiences during travel in the VE. This can be caused by poor interactive metaphors or by experiences which do not agree with the user's everyday understanding of the real world. This paper focuses on the navigation method in the VE, one of the major interfaces for the interactivity between human and VE in virtual reality circumstances and worlds. It proposes a new navigation method. Intelligent Cruise-Control Navigation (ICCN), which provides a natural and user-centred approach to navigation in the VE and can improve the user's sense of reality and presence. ICCN is composed of three major phases: Constant Velocity Navigation, Collision Detection and Avoidance, and Path Adjustment. The ICCN can reduce the user's fatigue and improve the user's presence in the VE. The small experimental study reported in this paper suggests that the ICCN will be a natural, straightforward, and useful navigation interface in VE.     

The physiological mirror—a system for unconscious control of a virtual environment through physiological activity

This paper introduces a system for real-time physiological measurement, analysis, and metaphorical visualization within a virtual environment (VE). Our goal is to develop a method that allows humans to unconsciously relate to parts of an environment more strongly than to others, purely induced by their own physiological responses to the virtual reality (VR) displays. In particular, we exploit heart rate, respiration, and galvanic skin response in order to control the behavior of virtual characters in the VE. Such unconscious processes may become a useful tool for storytelling or assist guiding participants through a sequence of tasks in order to make the application more interesting, e.g., in rehabilitation. We claim that anchoring of subjective bodily states to a virtual reality (VR) can enhance a person’s sense of realism of the VR and ultimately create a stronger relationship between humans and the VR.     

Presence: a unique characteristic in educational virtual environments

This article investigates the effect of presence on learning outcomes in educational virtual environments (EVEs) in a sample of 60 pupils aged between 11 and 13 years. We study the effect of personal presence, social presence and participant’s involvement on certain learning outcomes. We also investigate if the combination of the participant’s representation model in the virtual environment (VE) with the way it is presented gives a higher sense of presence that contributes to learning outcomes. Our results show that the existence of an avatar as the pupils’ representation enhanced presence and helped them to successfully perform their learning tasks. The pupils had a high sense of presence for both cases of the EVE presentation, projection on a wall and through a head mounted display (HMD). Our socialized virtual environment seems to play an important role in learning outcomes. The pupils had a higher sense of presence and completed their learning tasks more easily and successfully in the case of their egocentric representation model using the HMD.     

The pleasure of being (there?): an explorative study into the effects of presence and identification on the enjoyment of an interactive theatrical performance using omnidirectional video

This study explores how participants in an immersive theatrical performance perceive their role in the virtual environment (VE) and the effects of this perception on how they experience the performance as a whole. Using a quasi-experimental 2 × 2 design, narrative and task-based search was manipulated to explore the effects on spatial presence, social presence, identification and enjoyment. Results show that the effect of spatial presence on enjoyment of the performance is entirely mediated by identification with the role of the self in the VE. This could have interesting consequences for the experience of more narrative VE’s and suggests that the role of identification is something to explore further in future presence research.     

Predicting real-world ergonomic measurements by simulation in a virtual environment

Virtual reality techniques have been increasingly used for ergonomic applications. However, it is always important to know whether the results obtained in a virtual environment (VE) are representative of a real environment (RE) ones. This paper presents our preliminary experimental results on the relationship between ergonomic measurements in VE and RE for some typical “drilling” tasks. The same tasks were carried out by thirty male manufacturing factory workers in both VE and RE. Five evaluation indices - three objective (elbow angle, maximum force capacity reduction, and task completion time) and two subjective (BPD - Body Part Discomfort and RPE - Rated Perceived Exertion) - were used to evaluate the similarities between VE and RE for the selected “drilling” tasks. Four of these indices (all except elbow angle) were significantly higher (p < 0.05) in VE than in RE, which indicates that subjects experienced more discomfort and grew fatigued more quickly in VE. However, linear correlations (Pearson’s rho: 0.635-0.807) between VE and RE were found for two of the five indices (BPD and maximum force capacity reduction).

Relevance to industry

Using digital mock-ups and virtual reality simulations, industrial work activities can be evaluated to identify potential ergonomic problems during an early design stage, which reduces design time and costs, increases quality and improves customer satisfaction. A validated linear relationship can provide a reference for work design in virtual reality.     

Reflection and Refraction on Implicit Surfaces

Implicit surfaces are often used in computer graphics. They can be easily modeled and rendered, and many objects are composed of them in our daily life. In this paper, based on the concept of virtual objects, a novel method of real-time rendering is presented for reflection and refraction on implicit surface. The method is used to construct virtual objects from real objects quickly, and then render the virtual objects as if they were real objects except for one more step of merging their images with the real objects＇ images. Characteristics of implicit surfaces are used to compute virtual objects effectively and quickly. GPUs （Graphics Processing Units） are used to compute virtual vertices quickly and further accelerate the computing and rendering processes. As a result, realistic effects of reflections and refractions on implicit surfaces are rendered in real time.     

基于光学映射虚物体的并行绘制

尽管当前基于全局光照模型的图形绘制方法可以渲染出高质量的图象 ,但因为其计算量巨大 ,难以适用于诸如建筑物漫游、虚拟现实等对绘制速度有严格要求的场合 .为此引入光学映射虚物体的概念 ,利用构建在联网PC机上的集群系统 ,并行创建反射和折射虚物体 ,然后利用集群中各节点的图形加速硬件 ,像处理实际三维物体一样绘制这些虚物体 ,可以快速地绘制出反射 /折射效果的图象 .实验结果证明 ,该方法利用 CU P的计算能力和图形硬件的加速特性实现了真实感图形的高性能绘制 ,特别适用于诸如建筑物漫游、计算机动画和虚拟现实等要求交互式绘制的场合     

An ethnographic, action-based approach to human experience in virtual environments

This paper addresses a sensitive issue, of presence experienced by people interacting with a virtual environment (VE). Understanding ‘presence’, both theoretically and empirically, is important for designers interested in building effective computer-mediated environments for learning and work activities. The concept of presence has been treated mostly as a state of mind, to be investigated through ‘objective’ and ‘subjective’ measurement devices. The authors propose to add a different approach, which can address presence as an action-based process. This approach considers presence as the ongoing result of the actions performed in an environment and the local and cultural resources deployed by actors. In this sense, ‘presence’ can be captured by monitoring the sequence of participants’ actions and the aspects of the environment that are involved in this process; discourse/interaction analysis represents a fitting method for this goal. Sequences of interaction with a virtual library are used to illustrate some core aspects of an ethnographic, action-based approach to presence, such as the action possibilities envisaged by participants, the configuration of the virtual objects, the norms that regulate the interaction, the resources that are imported in the VE. These aspects are a necessary step to understand users’ presence in the VE and to plan consequent interventions to ameliorate the design of the interface.     

Evaluation of Internal and External Validity of a Virtual Environment for Learning a Long Procedure

Virtual reality is a frequently used tool in vocational training. Nevertheless, its efficiency has not been systematically tested. The main goal of this study is to assess the effectiveness of a virtual environment (VE) for learning a complex procedure in the biomedical domain. Two experiments were performed. The first one assessed internal validity of the VE, which is the effectiveness of using a VE in the process of learning a new procedure. The second one tested external validity of the VE, which is the participants’ ability to reproduce the acquired skills in a real context. We find that internal and external validity must be evaluated before using a virtual environment in long-term procedure learning. The results of such evaluations are a basis for future experiments aiming to optimize learning conditions in a VE and transferring the acquired skills in a real context.     

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.     

Way-finding during a fire emergency: an experimental study in a virtual environment

The way-finding behaviour and response during a fire emergency in a virtual environment (VE) was experimentally investigated. Forty participants, divided into two groups, were required to find the emergency exit as soon as possible in a virtual hotel building because of a fire escape demand under condition 1 (VE without virtual fire, control group) and condition 2 (VE with virtual fire, treatment group). Compared to the control group, the treatment group induced significantly higher skin conductivity and heart rate, experienced more stress, took longer time to notice the evacuation signs, had quicker visual search and had a longer escape time to find the exit. These results indicated that the treatment condition induced higher physiological and psychological stress, and had influenced the escape behaviour compared to the control group. In practice, fire evacuation education and fire evacuation system design should consider the response characteristics in a fire emergency.     

Perceiving interpersonally-mediated risk in virtual environments

Using virtual reality (VR) to examine risky behavior that is mediated by interpersonal contact, such as agreeing to have sex, drink, or smoke with someone, offers particular promise and challenges. Social contextual stimuli that might trigger impulsive responses can be carefully controlled in virtual environments (VE), and yet manipulations of risk might be implausible to participants if they do not feel sufficiently immersed in the environment. The current study examined whether individuals can display adequate evidence of presence in a VE that involved potential interpersonally-induced risk: meeting a potential dating partner. Results offered some evidence for the potential of VR for the study of such interpersonal risk situations. Participants’ reaction to the scenario and risk-associated responses to the situation suggested that the embodied nature of virtual reality override the reality of the risk’s impossibility, allowing participants to experience adequate situational embedding, or presence.     

Impact of multimodal feedback on simulated ergonomic measurements in a virtual environment: A case study with manufacturing workers

The purpose of this study was to evaluate the impact of multimodal feedback on ergonomic measurements in a virtual environment (VE) for a typical simulated drilling task. In total, sixty male manufacturing industry workers were divided into five groups. One group performed the working task in a real environment (RE), and ergonomic measurements for this group were used as the baseline for evaluation. The other four groups performed the same task in a virtual environment with different feedback treatments (visual with or without auditory and/or tactile feedback). Five indices – task completion time, maximum force capacity reduction, body part discomfort, rated perceived exertion, and rated task difficulty – were used to evaluate the measurements of each of the four treatments in VE in comparison to the baseline group in RE. The results indicate that the five indices for each of the four treatment groups were significantly higher than those of the RE group. Moreover, the indices of the visual‐only group were significantly higher than those of the other three groups with auditory and/or tactile feedback treatments. The findings of this study can provide a guideline for ergonomic evaluations of work designs in VE and for establishing a virtual reality simulation system. © 2011 Wiley Periodicals, Inc.     

Multiuser 3D virtual simulation environments support in the Gnutella peer-to-peer network

One of the challenges for 3D multiuser virtual simulation environments (3DMUVEs) developers is to keep the shared virtual simulation environment synchronized among all the participating users’ terminals. Support to 3DMUVEs through traditional client–server communication model offers simpler management but can lead to bottlenecks and higher latencies. Peer-to-peer communication model, on the other hand, offers no central coordination but are more complex to manage. Current peer-to-peer networks, such as KaZaA and Gnutella, provide multimedia sharing services but do not support multiuser 3D virtual environment (VE) applications.This paper describes a solution to support 3DMUVEs in a hybrid peer-to-peer Gnutella network, which provides session control and distributed shared VE synchronization. As a result of this work, two components specified by the ongoing multiuser extension to the MPEG-4 standard were implemented and integrated to the Gnutella network for control and synchronization. This solution minimizes the disadvantages of client–server and pure peer-to-peer models. The results show that this approach can be a feasible solution, specially for spontaneous 3DMUVEs that can emerge from any user, with no investment needed (apart from his own computer). The use of peer-to-peer networks such as the Gnutella could be used as a test environment for companies wishing to check both their multiuser 3DMUVEs software for correctness and their acceptance by the users community before making heavy investments.     

Virtual environments applications and applied ergonomics

The usability of virtual environments has attracted considerable efforts from ergonomists. Work has included studies of the side or after effects of participation in a virtual environment (VE) as well as the appropriateness of the Virtual Reality hardware and software interfaces and the understanding of factors which determine participant performance. Equally important for applied ergonomics is to understand how best to specify, build, implement and evaluate virtual environment solutions to everyday industrial, commercial, educational and medical problems. The potential value of ergonomics applied to virtual environments, and vice versa, are discussed. Two particular instances of VE development relevant to applied ergonomics are described - structured development and evaluation of industrial training and participatory redesign of workplaces. This paper is one of a number of contributions to a special issue on ergonomics in the study and use of virtual environments.     

Responding to a fire emergency in a virtual environment: different patterns of action for different situations

This paper presents an experimental study of participants' response to the sudden appearance of a fire emergency in a virtual environment (VE) and of the adaptivity of their response pattern. A VE has been built in which participants meet two situations: first an explorative navigation and afterwards a hurried escape from the unexpected outbreak of fire. Fire intensity and participants' distance from the exit at the outbreak of fire have been varied as well, to create different degrees of danger and different degrees of difficulty in the task of leaving the premises. Participants' action has been collected automatically for quantitative analysis by registering each individual activation of the interaction devices (a triple button joystick). In addition, the movements in both virtual and real environment of additional groups of participants have been videorecorded for qualitative analysis. Results show that the appearance of the fire emergency triggers important changes in the way people move in the VE, and that such changes are all adaptive responses to an emergency situation. In conclusion, people show recognition of a dangerous situation in a VE and readily produce adaptive responses, making the VE suitable for emergency simulations and for use as an effective training tool.     

Manipulating Objects in Virtual Worlds: Categorization and Empirical Evaluation of Interaction Techniques

The acceptance of virtual environment (VE) technology requires scrupulous optimization of the most basic interactions to maximize user performance and provide efficient and enjoyable virtual interfaces. Motivated by insufficient understanding of human factors implications in the design of interaction techniques for object manipulation in virtual worlds, this paper presents results of a formal study that evaluated two basic interaction metaphors for virtual manipulation—virtual pointer and virtual hand—in object selection and positioning tasks. In this work, we survey and categorize current virtual manipulation techniques according to their basic design metaphors, conduct experimental studies of the most basic techniques, and derive guidelines to aid designers in the practical development of VE applications.