Seeing size and feeling weight: the size-weight illusion in natural and virtual reality

OBJECTIVE: We experimentally tested the degree that the size-weight illusion depends on perceptual conditions allowing the observer to assume that both the visual and the kinesthetic stimuli of a weight seen and lifted emanate from the same object. We expected that the degree of the illusion depended on the "realism" provided by different kinds of virtual reality (VR) used when the weights are seen in virtual reality and at the same time lifted in natural reality. BACKGROUND: Welch and Warren (1980) reported that an intermodal influence can be expected only if perceptual information of different modalities is compellingly related to only one object. METHOD: Objects of different sizes and weights were presented to 50 participants in natural reality or in four virtual realities: two immersive head-mounted display VRs (with or without head tracking) and two nonimmersive desktop VRs (with or without screening from input of the natural environment using a visor). The objects' heaviness was scaled using the magnitude estimation method. RESULTS: Data show that the degree of the illusion is largest in immersive and lowest in nonimmersive virtual realities. CONCLUSION: The higher the degree of the illusion is, the more compelling the situation is perceived and the more the observed data are in correspondence with the data predicted for the illusion in natural reality. This shows that the kind of mediating technology used strongly influences the presence experienced. APPLICATION: The size-weight illusion's sensitivity to conditions that affect the sense of presence makes it a promising objective presence measure.     

The benchmark framework and exploratory study to investigate the feasibility of 360-degree video-based virtual reality to induce a full body illusion

Virtual Reality - The feeling of ownership of a virtual body has been a topic of interest in recent years. In order to observe the mechanisms involved in the perception of the body illusion and its...     

Effects of speed,complexity and stereoscopic VR cues on cybersickness examined via EEG and self-reported measures

This study evaluated the interplay between environmental cues in virtual reality (VR) and cybersickness as experienced by users of head-mounted displays (HMDs). Utilizing electroencephalogram (EEG) data and self-reported discomfort measures, the effects of three major VR cues – speed, scene complexity, and stereoscopic rendering – on cybersickness were examined, with the latter being of particular interest as it had not previously been studied explicitly in the context of VR-HMDs. Self-reported discomfort was assessed through in-VR single-item queries and post-VR simulator sickness questionnaires, accounting for both immediate and persistent cybersickness, respectively, and over three experiment sessions, accounting for the effects of accumulation. Analysis revealed connections that indicate a relationship between EEG data and the presence of cybersickness for all three cue types. Significant differences were observed in EEG relative power changes between the trials where cybersickness was and was not reported. EEG relative power changes were also linked to both immediate and persistent cybersickness, especially in the theta and gamma frequency bands. The increase in immediate discomfort with the stereoscopic rendering cues over successive sessions suggests a decrease in tolerance to these effects over time.     

Virtual grasps recognition using fusion of Leap Motion and force myography

Hand gesture recognition is important for interactions under VR environment. Traditional vision-based approaches encounter occlusion problems, and thus, wearable devices could be an effective supplement. This study presents a hand grasps recognition method in virtual reality settings, by fusing signals acquired using force myography (FMG), a muscular activity-based hand gesture recognition method, and Leap Motion. We conducted an experiment where participants performed grasping of virtual objects with VR goggles on their head, an FMG band on their wrist, and a Leap Motion positioned either on the desk or on the goggles (two experimental settings). The FMG, Leap Motion, and fusion of both signals were used for training and testing a simple, but effective linear discriminant analysis classifier, as well as three other mainstream classification algorithms. The results showed that the fusion of both signals achieved a significant improvement in classification accuracy, compared to using Leap Motion alone in both experimental settings.     

Human–Computer Interface Issues in Controlling Virtual Reality With Brain–Computer Interface

We have integrated the Graz brain–computer interface (BCI) system with a highly immersive virtual reality (VR) Cave-like system. This setting allows for a new type of experience, whereby participants can control a virtual world using imagery of movement. However, current BCI systems still have many limitations. In this article we present two experiments exploring the different constraints posed by current BCI systems when used in VR. In the first experiment we let the participants make free choices during the experience and compare their BCI performance with participants using BCI without free choice; this is unlike most previous work in this area, in which participants are requested to obey cues. In the second experiment we allowed participants to control a virtual body with motor imagery. We provide both quantitative and subjective results, regarding both BCI accuracy and the nature of the subjective experience in this new type of setting.     

Human perception of a conversational virtual human: an empirical study on the effect of emotion and culture

Virtual reality applications with virtual humans, such as virtual reality exposure therapy, health coaches and negotiation simulators, are developed for different contexts and usually for users from different countries. The emphasis on a virtual human’s emotional expression depends on the application; some virtual reality applications need an emotional expression of the virtual human during the speaking phase, some during the listening phase and some during both speaking and listening phases. Although studies have investigated how humans perceive a virtual human’s emotion during each phase separately, few studies carried out a parallel comparison between the two phases. This study aims to fill this gap, and on top of that, includes an investigation of the cultural interpretation of the virtual human’s emotion, especially with respect to the emotion’s valence. The experiment was conducted with both Chinese and non-Chinese participants. These participants were asked to rate the valence of seven different emotional expressions (ranging from negative to neutral to positive during speaking and listening) of a Chinese virtual lady. The results showed that there was a high correlation in valence rating between both groups of participants, which indicated that the valence of the emotional expressions was as easily recognized by people from a different cultural background as the virtual human. In addition, participants tended to perceive the virtual human’s expressed valence as more intense in the speaking phase than in the listening phase. The additional vocal emotional expression in the speaking phase is put forward as a likely cause for this phenomenon.     

Using auditory event-related EEG potentials to assess presence in virtual reality

The feeling of presence in a virtual reality (VR) is a concept without a standardized objective measurement. In the present study, we used event-related brain potentials (ERP) of the electroencephalogram (EEG) elicited by tones, which are not related to VR, as an objective indicator for the presence experience within a virtual environment. Forty participants navigated through a virtual city and rated their sensation of being in the VR (experience of presence), while hearing frequent standard tones and infrequent deviant tones, which were irrelevant for the VR task. Different ERP components elicited by the tones were compared between participants experiencing a high level of presence and participants with a low feeling of presence in the virtual city. Early ERP components, which are more linked to automatic stimulus processing, showed no correlation with presence experience. In contrast, an increased presence experience was associated with decreased late negative slow wave amplitudes, which are associated with central stimulus processing and allocation of attentional resources. This result supports the assumption that increased presence is associated with a strong allocation of attentional resources to the VR, which leads to a decrease of attentional resources available for processing VR-irrelevant stimuli. Hence, ERP components elicited by the tones are reduced. Particularly, frontal negative slow waves turned out to be accurate predictors for presence experience. Summarizing, late ERPs elicited by VR-irrelevant tones differ as a function of presence experience in VR and provide a valuable method for measuring presence in VR.     

My hands? Importance of personalised virtual hands in a neurorehabilitation scenario

We have developed a novel and affordable way to texture virtual hands from individually taken photographs and integrated the virtual hands into a mixed reality neurorehabilitation system. This mixed reality system allows for serious game play with mirrored and non-mirrored hands, designed for patients with unilateral motor impairments. Before we can ethically have patients use the system, we must show that embodiment can be achieved for healthy users. We compare our approach’s results to previous work in the field and present a study with 48 healthy (non-clinical) participants targeting visual fidelity and self-location. We show that embodiment can be achieved for mirrored and non-mirrored hand representations and that the higher realism of virtual hands achieved by our texturing approach alters perceived embodiment. We further evaluate whether using virtual hands resized to the individual’s hand size affects embodiment. We present a 16-participant study where we could not find a significant difference with personal resized hands. In addition to rehabilitation contexts, our findings have implications for the design and development of applications where embodiment is of high importance, such as surgical training and remote collaboration.

     

虚拟手交互中约束类物体操作研究

虚拟手技术是虚拟现实技术中的一种交互方式，是指通过手势识别技术将人的真实手映射到虚拟环境中并与虚拟物体进行交互操作的人机交互方式。主要应用于虚拟训练、虚拟手术和虚拟装配等领域。对虚拟手交互的约束类对象进行了研究，提出了基于运动学的约束类物体操作方法，解决了阀门类有约束物体交互中虚拟手姿态不真实、操作不可控的问题。设计实验验证了基于运动学的方法能以符合实际操作的效果完成虚拟现实系统中的操作任务，可以应用到虚拟训练、虚拟装配等仿真平台。     

Interfaces That Heal: Coupling Real and Virtual Objects to Treat Spider Phobia

Tactile augmentation is a simple, safe, inexpensive interaction technique for adding physical texture and force feedback cues to virtual objects. This study explored whether virtual reality (VR) exposure therapy reduces fear of spiders and whether giving patients the illusion of physically touching the virtual spider increases treatment effectiveness. Eight clinically phobic students were randomly assigned to one of 3 groups-(a) no treatment, (b) VR with no tactile cues, or (c) VR with a physically "touchable" virtual spider-as were 28 nonclinically phobic students. Participants in the 2 VR treatment groups received three 1-hr exposure therapy sessions resulting in clinically significant drops in behavioral avoidance and subjective fear ratings. The tactile augmentation group showed the greatest progress on behavioral measures. On average, participants in this group, who only approached to 5.5 ft of a live spider on the pretreatment Behavioral Avoidance Test (Garcia-Palacios, 2002), were able to approach to 6 in. of the spider after VR exposure treatment and did so with much less anxiety (see www.vrpain.com for details). Practical implications are discussed.     

On the Efficiency of a VR Hand Gesture-Based Interface for 3D Object Manipulations in Conceptual Design

In the early stages of 3D design, sketches are used to quickly conceptualize ideas and gain insight into problems and possible solutions. Computer-aided design tools are widely used for 3D modeling and design, but their required precision and 2D mouse and screen-based interface inhibit the flow of ideas. A study was conducted to explore the efficiency of hand tracking and virtual reality (VR) for 3D object manipulations in conceptual design. Based on existing research on conceptual design and hand gestures, an intuitive hand-based interaction model is proposed. An experiment on basic 3D manipulation shows that participants using a simple VR and hand-tracking interface prototype have similar performance to those using a traditional mouse and screen interface. For the improvement of gestural conceptual design interfaces, the relevant issues are identified.     

Effects of postural stability,active control,exposure duration and repeated exposures on HMD induced cybersickness

Cybersickness is common during head-mounted display (HMD) based virtual reality. This study examined whether it is possible to: (1) identify people who are more susceptible to this cybersickness; and (2) find general ways to reduce its occurrence and severity. Our participants were exposed to HMD-based virtual reality four times over two different days (using “Freedom Locomotion VR”). During these 10-min trials, participants were either free-standing or posturally restrained as they actively controlled or passively viewed their locomotion through the virtual environment. Cybersickness was found to increase steadily over time during each exposure. While this cybersickness was markedly reduced on day 2 (compared to day 1), it was not significantly altered by either the use of postural restraints or active locomotion control. However, the sick and well participants in our study were found to differ in terms of their spontaneous postural activity (before they entered virtual reality). We found that the participants who experienced stronger vection also tended to report more severe cybersickness in this study. These findings suggest that we should be able to identify people who are more susceptible to cybersickness and help them become more resistant to it (via repeated exposures to HMD-based virtual reality).     

Assessing the influence of repeated exposures and mental stress on human wayfinding performance in indoor environments using virtual reality technology

This study aimed to examine the effect of repeated exposures to indoor environments on people’s indoor wayfinding performance, both under normal condition and during fire emergency which could induce significant mental stress. Indoor wayfinding experiments were conducted in an immersive virtual museum developed using virtual reality technologies. Participants of the experiments were divided into three groups, who participated in one, two and three trials, respectively. Those who participated in more than one trial were given an interval of two weeks between two consecutive trials. Each trial of the experiment included a treasure hunting task and an egress task. Participants were presented with a virtual fire emergency during the egress task of their last trial. Data of wayfinding performance measures of the participants, as well as their physiological and emotional responses, sense of direction, wayfinding anxiety and simulator sickness were collected and analyzed. The results revealed significant positive impact of repeated exposure on participants’ wayfinding performance, which resulted in a decrease in the time needed to complete the treasure hunting task. The results also revealed significant negative impact of mental stressed caused by the fire emergency on participants’ wayfinding performance, which led to increased travel time and distance during egress. Such negative impact of stress, however, could be noticeably diminished by the repeated exposures, showing significant interaction effect between these two factors.     

Evaluation of customer impressions using virtual prototypes in the internet environment

This study aims to investigate a cost effective and efficient way of analyzing customer impressions on design alternatives by incorporating the benefits of virtual prototyping into the Internet-based experimental environment. It is hypothesized that the results of the Internet-based experiment using the images of virtual prototypes are comparable to those of the virtual reality-based environment using virtual prototypes. Two experiments were conducted. In the virtual reality environment, participants were employed to evaluate virtual prototypes while in the Internet environment participants evaluated images of the same virtual prototypes from their own places. For each experiment, 16 male participants were employed to evaluate 32 different virtual prototypes generated from the combination of 17 design elements of automobile interior. The results of the experiments indicated that there were no significant differences between the two experimental methods while the Internet environment-based method could save considerable time and efforts for experimentation. This study concludes that the Internet-based evaluation method using the images of virtual prototypes could be a cost effective and efficient way of analyzing customer impressions on design alternatives.

Relevance to Industry

This study showed that the results of the Internet-based evaluation method using the images of virtual prototypes are comparable to those of the virtual reality-based method using real virtual prototypes. The Internet-based evaluation method could be used as a cost effective and efficient way of collecting and analyzing various customers’ impressions on design alternatives at the early stage of product development process.     

基于虚拟现实的渲染优化算法

随着虚拟现实技术的不断发展，对虚拟场景的真实度要求也越来越提高.然而在虚拟场景中，复杂的地形、大量的植被和建筑使需要渲染的数据量大得惊人，故渲染速度成为了虚拟现实技术的一大瓶颈.现有的研究并不能很好的提升虚幻引擎中的渲染速度，还会出现“突越”和对视野外模型剔除效果差的问题.本文提出一种游戏线程与渲染线程并行和双层裁剪算法.首先在虚幻引擎中将游戏线程与渲染线程并行以提升渲染速度，然后使用淡入淡出细节层次算法进行第一层裁剪，最后使用缓慢剔除算法进行第二层裁剪，提升剔除效果.实验证明，该方法与串行线程相比渲染速度提升了40%，与传统单层裁剪算法相比，帧率也达到了55.     

The size-weight illusion in team lifting

The purpose of these studies was to examine whether or not there is a size-weight illusion when participants lift containers as a team. In Experiment 1, teams of participants lifted a set of 16 containers that varied in mass and size and reported their perceptions of heaviness and volume. In Experiment 2, participants lifted the same containers individually. A size-weight illusion was demonstrated in each experiment: Reports of perceived heaviness decreased substantially as the volumes of the containers increased for both styles of lifting. However, both the magnitude of the illusion and mean perceived heaviness were greater in the team lift. Actual or potential applications of this research include the development of safe lifting guidelines for team lifting.     

Homuncular Flexibility in Virtual Reality

Immersive virtual reality allows people to inhabit avatar bodies that differ from their own, and this can produce significant psychological and physiological effects. The concept of homuncular flexibility (Lanier, 2006) proposes that users can learn to control bodies different from their own by changing the relationship between tracked and rendered motion. We examine the effects of remapping movements in the real world onto an avatar that moves in novel ways. In Experiment 1, participants moved their legs more than their arms in conditions where leg movements were more effective for the task. In Experiment 2, participants controlling 3‐armed avatars learned to hit more targets than participants in 2‐armed avatars. We discuss the implications of embodiment in novel bodies.     

On the formulation of competitive negotiations in Web applications: The Latin-American market case

Work on electronic negotiation has motivated the development of systems with strategies specifically designed to establish protocols for buying and selling goods on the Web. On the one hand, there are systems where agents interact with users through dialogues and animations, helping them to find products while learning from their preferences to plan future transactions. On the other hand, there are systems that employ knowledge-bases to determine the context of the interactions and to define the boundaries inherently established by the e-Commerce. This paper introduces the idea of developing an agent with both capabilities: negotiation and interaction in an e-Commerce application via virtual reality (with a view to apply it in the Latin-American market, where both the technological gap and an inappropriate approach to motivate electronic transactions are important factors). We address these issues by presenting a negotiation strategy that allows the interaction between an intelligent agent and a human consumer with Latin-American idiosyncrasy and by including a graphical agent to assist the user on a virtual basis. We think this may reduce the impact of the gap created by this new technology.     

Processing presence: how users develop spatial presence through an immersive virtual reality game

Virtual Reality - A primary affordance of virtual reality (VR) headsets is to give the user spatial presence or the illusion of being in the virtual environment. Although considerable research...