虚拟选煤厂三维模型系统的实时性优化

虚拟现实模型系统的优化对于提高运行系统的实时性,保证虚拟现实系统的沉浸、交互等特性具有重要作用.结合虚拟选煤厂三维模型系统的优化,分析和探讨了虚拟现实模型系统实时性优化的几项关键技术,包括优化三维模型结构,节省模型系统的多边形开销,使系统中总多边形数不超过硬件的处理能力;优化纹理数据,在保证必要的纹理细节的前提下,有效节约纹理内存;优化模型数据库和LOD层次结构,改善运行系统的数据筛选性能,提高绘制速度.模型系统优化后系统的剔除和绘制时间曲线表明,优化后系统运行的实时性得到了有效提高.     

虚拟环境中履带式车辆运动仿真

为了对虚拟环境中履带车辆进行建模,满足虚拟现实系统沉浸感和实时性要求,研究了基于ODE(多体动力学仿真库)的履带式车辆多体动力学模型和仿真方法.将模型应用于虚拟现实系统,对履带车辆运动、翻越垂直墙、壕沟等障碍进行实时仿真.结果表明该模型能较好地表现虚拟环境中履带式车辆运动的动态过程,以及履带、负重轮等行走系统部件的相对运动.提出的模型及仿真方法能较好地应用于虚拟战场、装备模拟训练系统等虚拟环境,具有一定的应用价值.     

支持协同工作的VRML网络虚拟现实系统

针对网络通信的带宽和延时问题,是制约网络虚拟现实发展与普及的关键因素.为解决实时性传输问题,通常的做法是将网络虚拟现实系统建立在高性能计算机、宽带网络、以及新的网络协议(如VRTP)之上,造成代价过高.为了在不改变现有网络带宽和网络协议的前提下实现CSCW,提出一种支持协同工作的VRML网络虚拟现实系统.通过利用细节层次模型和按需传输方法,实现了用户工作空间的快速生成;通过构建多用户通信环境和构造通信数据包,保证了通信的实时性;通过引入操作令牌思想和碰撞检测技术,实现了对象模型的协同并行控制.通过仿真实例,结果表明,提出的网络虚拟现实系统满足低带宽、实时性要求,碰撞检测机制合理,具有一定的实用价值.     

纹理映射在模型优化中的应用

三维模型的构建是虚拟现实及视景仿真系统中最基本、最重要的组成部分之一。构建三维模型需考虑到场景浏览的真实感与实时性,因而需要建立一个最优化的可视化模型。本文比较了在虚拟现实系统中模型优化的方法,采用了纹理映射代替多边形建模创建高效真实感模型的优化手段,着重介绍了颜色纹理和凹凸纹理的相关理论和方法,并应用于视景仿真系统中,极大的提高了实时性,并保证了真实感。     

基于Creator的复杂场景建立方法的研究与实现

内含大量设备模型的场景是虚拟现实应用的典型场景.文章阐述了在虚拟场景构造中大规模复杂场景的建模与优化、场景数据库优化、CAD模型显示与优化、数据格式优化等关键技术问题,实现了整个系统的设计与开发.实验证明该系统具有良好的交互性与实时性.     

虚拟现实综述

虚拟现实是人类在探索自然过程中创造形成的一种用于认识自然、模拟自然,进而更好地适应和利用自然的科学方法和技术.文中在分析虚拟现实全过程的基础上,给出虚拟现实问题的不同分类及一种理论表达,并抽象出虚拟现实领域的三大科学技术问题类;在此基础上从虚拟现实中的建模方法、虚拟现实表现技术、人机交互及设备、虚拟现实开发平台与支撑环境和虚拟现实应用等几个方面论述了虚拟现实当前的主要研究目标、研究成果和发展趋势;最后指出虚拟现实需要进一步致力研究解决的若干理论和技术问题.     

基于OpenGL与粒子系统的喷泉模拟实现

喷泉效果能够极大地增强虚拟现实系统的沉浸感,在计算机动画、计算机游戏等领域有着广泛的应用,对喷泉的模拟也能够促进计算机仿真技术的发展.粒子系统是模拟喷泉的一种有效方法,文中基于OpenGL与粒子系统来实现喷泉模拟,基本思想是运用粒子系统建模方法分析喷泉水体模型,重点研究喷泉水珠粒子产生、运动和消失的机理,采用OpenGL显示列表方法和纹理映射技术增强喷泉绘制过程中的渲染和真实感.最后,在PC机上运用VC++6.0开发工具和OpenGL实现喷泉模拟,实验证明该方法具有很好的实时性和逼真性.     

虚拟现实场景的建模特点及生成效果

在分析了基于实景的虚拟现实场景建模特点的基础上,运用一个具体的实例来阐述了基于实景的虚拟现实场景的生成过程及其相关注意事项,通过合理建模减小复杂度、通过真实感贴图来增强逼真度、通过模型导入的对象化来实现对虚拟物体的控制。最终在逼真性,实时性和可控性方面都达到了较好的效果。     

基于真实景物的虚拟现实场景的生成

在分析基于实景的虚拟现实场景建模特点的基础上,运用一个具体的实例来阐述了基于实景的虚拟现实场景的生成过程及其相关注意事项,通过合理建模减小复杂度、通过真实感贴图来增强逼真度、通过模型导入的对象化来实现对虚拟物体的控制、最终在逼真性、实时性和可控性方面都达到了较好的效果。     

速度驱动的复杂场景多层级力觉交互算法

触/力觉交互技术应用环境的复杂化,对复杂触/力觉场景的研究提出了新的挑战.文中以虚拟现实牙科手术训练系统为背景,研究基于速度驱动的复杂场景多层级力觉交互算法.文中采用CATIA对下牙列大量数据进行网格简化,建立了下牙列场景的层次细节(Levels Of Detail,LOD)模型;基于人类触觉感知的精度随交互速度的变化规律,设计了速度驱动的LOD模型触发机制;提出了虚拟工具化身SCP(Surface Contact Point)层级映射算法,保证了力觉交互设备的稳定性,并发现了映射约束线段的长度是保证力觉逼真性及实时性协调的关键变量;最后,设计了针对一般儿何体和复杂曲面的实验,量化评价文中算法的逼真性及实时性,证明了将人手运动速度作为场景模型复杂度切换驱动条件的有效性.     

一种基于视沉的增强现实三维注册算法

为了提高增强现实系统三维注册的精度和效率，提出了一种基于计算机视觉的增强现实三维注射算法，并已将其用于采用透射式头盔显示器的增强现实系统中，该算法有如下特点：（1）构架简单，实用性强，一般情况下只需4个平面标志物就可实现三维注册；（2）工作范围大，甚至可以应用到室外的增强现实系统中；（30数值求解过程最线性过程，误差小，可以满足增强现实系统高精度三维注册的要求，另外，应用这种算法所需要作的图象处理计算量很小，其典型系统包括一个彩色CCD和几个不同颜色的标志点，由于很容易获得标志点的对应像面位置，而且不需要计算图象对，因此实时性好，是一般图形工作站和PC机上的增强现实系统进行实时注册的算法基础。     

Evaluation of quality and personalisation of VR/AR/MR learning systems

ABSTRACT

The paper aims to analyse the problem of quality evaluation and personalisation of virtual reality/augmented reality/mixed reality (VR/AR/MR). First of all, systematic review of relevant scientific literature on the research topic was conducted. After that, findings of the systematic review concerning evaluation of quality and personalisation of VR/AR/MR learning environments are presented. The author’s VR/AR/MR learning systems/environments quality evaluation and personalisation framework is also presented in the paper. Evaluation of quality of VR/AR/MR platforms/environments should be based on (a) applying both expert-centred (top-down) and user-centred (bottom-up) quality evaluation methods and (b) separating ‘internal quality’ criteria, and ‘quality in use’ criteria in the set of quality criteria (model). Personalisation of VR/AR/MR platforms/environments should be based on learners’ models/profiles using students’ learning styles, intelligent technologies, and Semantic Web applications.     

增强现实综述

增强现实(augmented reality，AR)技术可以将虚拟的物体合并到现实场景中，并能支持用户与其进行交互，它已经成为虚拟现实研究中的一个重要领域，也是人机界面技术发展的一个重要方向。为了使人们对其有所了解，该文首先概略描述了这个领域的主要研究内容和进展情况，并详细介绍了增强现实中的支撑技术、开发工具和相关理论；然后针对当前AR应用的现状，分析了实现中的难点问题，并给出了与AR普及应用密切相关的一些系统框架和开发平台的描述，最后介绍了几个典型的AR应用实例。     

Experimental research into human cognitive processing in an augmented reality environment for embedded training systems

Research into human factors issues associated with the use of augmented reality (AR) technology is very limited. Consequently, there is a need for formal human factors design guidelines to underpin the integration of AR into systems. The Defence Evaluation and Research Agency (DERA) Centre for Human Sciences (CHS) is evaluating the potential of AR for providing real-time training feedback in future advanced embedded training systems for the military. In order to understand the important human factors issues of augmented reality, DERA funded the Advanced VR Research Centre (AVRRC) at Loughborough University to investigate the cognitive ergonomics of this technology. An important aspect of this research is concerned with identifying any human information processing issues that may arise when information is presented via AR and overlaid upon one or more primary display surfaces such as a visual display unit (VDU). Two main issues are addressed in this research. First, the impact of AR on human information processing and second, subjective workload experienced when displaying information via the AR medium. The experiments reported in this paper assess issues of reaccommodation and reaction times to alarms on different display formats. They demonstrate also that AR performs as well as standard display formats.     

A Survey on Sketch Based Content Creation: from the Desktop to Virtual and Augmented Reality

Sketching is one of the most natural ways for representing any object pictorially. It is however, challenging to convert sketches to 3D content that is suitable for various applications like movies, games and computer aided design. With the advent of more accessible Virtual Reality (VR) and Augmented Reality (AR) technologies, sketching can potentially become a more powerful yet easy-to-use modality for content creation. In this state-of-the-art report, we aim to present a comprehensive overview of techniques related to sketch based content creation, both on the desktop and in VR/AR. We discuss various basic concepts related to static and dynamic content creation using sketches. We provide a structured review of various aspects of content creation including model generation, coloring and texturing, and finally animation. We try to motivate the advantages that VR/AR based sketching techniques and systems can offer into making sketch based content creation a more accessible and powerful mode of expression. We also discuss and highlight various unsolved challenges that current sketch based techniques face with the goal of encouraging future research in the domain.     

A method to measure the uniformity of the virtual image distance in an augmented reality or virtual reality device

The virtual image distance in an augmented reality (AR) or virtual reality (VR) device is an important factor in determining its performance. In this paper, a method for measuring the virtual image distance and its uniformity is proposed. The setup for measurement consists of a two-dimensional spatial sensor array on the translational stage and a pinhole array plate placed in front of the AR or VR device. As the distance between the pinhole plate and the two-dimensional spatial sensor array were changed, the positions of the rays through each pinhole were measured by a two-dimensional spatial sensor array. The ray trajectories through each pinhole were obtained by fitting these positions to straight lines. The relative distances between these ray trajectories were calculated with respect to the distance from the pinhole plate. This method is effective for measuring the uniformity, such as the azimuthal dependence of the virtual image distance or the dependence of the virtual image distance on the distance from the optical axis of the VR lens.     

A comparative study using an autostereoscopic display with augmented and virtual reality

Advances in display devices are facilitating the integration of stereoscopic visualisation in our daily lives. However, autostereoscopic visualisation has not been extensively exploited. In this paper, we present a system that combines augmented reality (AR) and autostereoscopic visualisation. We also present the first study that compares different aspects using an autostereoscopic display with AR and virtual reality (VR), in which 39 children from 8 to 10 years old participated. In our study, no statistically significant differences were found between AR and VR. However, the scores were very high in nearly all of the questions, and the children also scored the AR version higher in all cases. Moreover, the children explicitly preferred the AR version (81%). For the AR version, a strong and significant correlation was found between the use of the autostereoscopic screen in games and seeing the virtual object on the marker. For the VR version, two strong and significant correlations were found. The first correlation was between the ease of play and the use of the rotatory controller. The second correlation was between depth perception and the game global score. Therefore, the combinations of AR and VR with autostereoscopic visualisation are possibilities for developing edutainment systems for children.     

INTERVALES: INTERactive Virtual and Augmented framework for industriaL Environment and Scenarios

One of Industry 4.0’s greatest challenges for companies is the digitization of their processes and the integration of new related technologies such as virtual reality (VR) and augmented reality (AR), which can be used for training purposes, design, or assistance during industrial operations. Moreover, recent results and industrial proofs of concept show that these technologies demonstrate critical advantages in the industry. Nevertheless, the authoring and editing process of virtual and augmented content remains time-consuming, especially in complex industrial scenarios. While the use of interactive virtual environments through virtual and augmented reality presents new possibilities for many domains, a wider adoption of VR/AR is possible only if the authoring process is simplified, allowing for more rapid development and configuration without the need for advanced IT skills. To meet this goal, this study presents a new framework: INTERVALES. First, framework architecture is proposed, along with its different modules; this study then shows that the framework can be updated by not only IT workers, but also other job experts. The UML data model is presented to format and simplify the authoring processes for both VR and AR. This model takes into account virtual and augmented environments, the possible interactions, and ease operations orchestration. Finally, this paper presents the implementation of an industrial use case composed of collaborative robotic (cobotic) and manual assembly workstations in VR and AR based on INTERVALES data.     

Sense of Immersion in Computer Games Using Single and Stereoscopic Augmented Reality

As a novel interaction and presentation technology, Augmented Reality (AR) has been widely used in education, tourism, entertainment, psychology, and many other applications. In the game industry, this revolutionary technology has introduced a new form of interaction between players and the gaming environment. In this article, we aim to find if exploiting AR in computer games can enhance the sense of immersion, and consequently, satisfying the players. To this end, a mobile game called Ladybug is implemented using three different techniques including the regular virtual reality (VR) camera, single AR camera, and stereoscopic AR camera. The results of a comprehensive user study on these techniques showed that the single AR camera and stereoscopic AR camera can result in more sense of immersion in players in comparison to the VR camera. However, the hypothesis that the stereoscopic AR results in more sense of presence in comparison to the single AR camera is rejected. On the other hand, our findings show that the AR stereoscopic camera can lead to a better emotional involvement and enjoyment in comparison to the single AR camera and VR camera.     

Depth perception in shuffleboard: Depth cues effect on depth perception in virtual and augmented reality system

The virtual reality (VR) and augmented reality (AR) applications have been widely used in a variety of fields; one of the key requirements in a VR or AR system is to understand how users perceive depth in the virtual environment and AR. Three different graphics depth cues are designed in shuffleboard to explore what kind of graphics depth cues are beneficial for depth perception. We also conduct a depth‐matching experiment to compare performance in VR and AR systems using an optical see‐through head‐mounted display (HMD). The result shows that the absolute error increases as the distance becomes farther. Analysis from the inverse of distance shows that box depth cues have a significant effect on depth perception, while the points depth cues and line depth cues have no significant effect. The error in diopter in AR experiment is lower than that in VR experiment. Participants in the AR experiment under medium illuminance condition have less error than those under low and high illuminance conditions. Men have less error than women in certain display conditions, but the advantage disappears when there is a strong depth cue. Besides, there is no significant effect of completion time on depth perception.