虚拟现实技术概述

“虚拟现实”就是一种可以创建和体验虚拟世界的计算机系统。这种系统生成的各种虚拟环境,作用于用户的视觉、听觉、触觉,使用户产生身临其境的感觉,沉浸其中。而所谓虚拟世界则是虚拟环境或给定仿真对象的集合虚拟现实是近年发展起来的一项新技术,目前已广泛地应用于许多领域。该文阐述了虚拟现实技术的产生、概念、特征及其意义、虚拟现实技术的技术组成和艺术、情感魅力,分析了虚拟现实技术的研究内容、方向和技术瓶颈。     

虚拟现实技术在电力培训中的应用

虚拟现实技术的出现,使现代教育培训发生了很大变化。究其原因主要是虚拟培训有着传统培训方式无法比拟的优势。虚拟教育培训是指利用虚拟现实技术来模拟现实生活中的环境,学员在培训的过程中始终感觉自己在现场进行真实培训。虚拟现实技术利用先进的交互设备在视觉、听觉、触觉上对虚拟环境中的事物进行感知,有利于实际操作技能的提高。该文论述了虚拟现实技术在教育培训应用中的必要性和优越性。以电力培训系统的构建为例,阐述了如何利用3DSM Max和OpenGL构建虚拟培训系统,实现了虚拟现实与教育培训的有机结合。     

基于虚拟现实技术的油田仿真培训系统的设计

油田作业培训的安全问题一直备受关注,为了保证油田作业培训的安全性,将虚拟现实技术应用于油田仿真培训工作,建立油田仿真培训系统.该系统基于虚拟现实技术,设计了油田仿真培训系统的总体结构,提出了演示、操作演练和考评三种培训模式,阐述了交互式菜单和对三维实体的交互式操作两种人机交互方式,引入了虚拟人和虚拟手的模型及控制技术.该系统虚拟场景逼真,培训功能齐全,用户可以进行多视点、多场景的浏览,让用户有身临其境的感觉,目前已经应用到实际培训中,效果良好.     

膝关节镜手术仿真训练系统设计

利用虚拟现实技术建立的手术仿真训练系统,可以大大减少内窥镜等疑难手术的培训时间并节约昂贵的动物实验费用.为满足膝关节镜手术训练的需要,针对虚拟手术仿真的技术特点,提出了关于虚拟现实技术的膝关节镜手术仿真训练系统的设计,主要对系统体系结构、软件结构、功能模块和系统界面的设计和技术实现进行了研究,最终实现了一个支持双手操作的手术仿真训练系统.实践证明,系统能逼真地模拟手术的流程,取得了良好的训练效果.     

虚拟现实技术在视景仿真系统中的应用

利用虚拟现实技术可以在仿真系统中构建出逼真的三维虚拟环境。讨论了虚拟现实技术的涵义和特征,重点研究了在实现一个视景仿真系统时所用到的关键虚拟现实技术,并给出了虚拟现实技术在一个军事模拟训练系统的三维战场视景仿真中的具体应用。     

基于VRML技术的虚拟产品可控性研究

虚拟现实（VR-virtual reality），也称虚拟实境或灵境，是一种可以创建和体验虚拟世界的计算机系统，它利用计算机技术生成一个逼真的、具有视、听、触等多种感知的虚拟环境。用户通过使用各种交互设备。同虚拟环境中的实体相互作用，使之产生身临其境感觉的交互式视景仿真和信息交流。是一种先进的数字化人机接口技术。 从本期专题可以看到：虚拟现实技术在机械行业有广泛的应用前景。虚拟设计对传统设计方法的革命性影响已经逐渐显现出来，虚拟现实技术与传统CAD／CAM技术的结合有着光辉的前景。     

虚拟现实系统中的视景仿真研究

视景仿真是虚拟现实系统的重要组成部分.文中讨论了建立虚拟现实系统的软硬件条件和视景仿真的建立过程,并给出了优化系统实时性能、减小视觉延迟和虚拟环境导航的办法.这些办法可有效减少系统计算量,优化交互性能.     

国防科大计算机学院工学博士学位论文摘要

分布式虚拟环境的建模语言、系统结构及其实现作者：王勇军（１９９８．１０）导师：胡守仁教授　李思昆教授　　由于网络技术的飞速发展,分布式虚拟环境系统及其开发工具对于虚拟现实技术的应用具有非常重大的意义。本文针对当前分布式虚拟环境系统对仿真计算单元的分布并行性开发不够充分和规范的缺点,从一个全新的角度来研究虚拟环境的建模语言及其分布式虚拟环境的系统结构,开创性地为虚拟环境技术的研究建立了一个全面可扩展的理论框架。本文将分布式系统的设计目标引入分布式虚拟环境,全面地讨论了分布式虚拟环境系统的设计方法,…     

双容水槽液位控制虚拟现实环境的建立与仿真

利用VRML构造器V-Realm Builder和Simulink的虚拟现实接口及模块建立双容水槽液位控制系统的虚拟现实环境和仿真控制结构图;同时通过虚拟环境中建立的调节阀交互式输入传感器节点,在虚拟环境中利用鼠标拖动该传感器节点控制第一个调节阀开度来控制进水流量,从而实现双容水槽中两个水槽的液位随进水流量变化的虚拟控制仿真.双容水槽液位控制系统的各参数可在仿真结构图中直接设置和修改.     

虚拟现实系统中的视景仿真研究

视景仿真是虚拟现实系统的重要组成部分。文中讨论了建立虚拟现实系统的软硬件条件和视景仿真的建立过程，并给出了优化系统实时性能、减小视觉延迟和虚拟环境导航的办法。这些办法可有效减少系统计算量，优化交互性能。     

Computer-based virtual reality simulator for phacoemulsification cataract surgery training

Recent research in virtual reality indicates that computer-based simulators are an effective technology to use for surgeons learning to improve their surgical skills in a controlled environment. This article presents the development of a virtual reality simulator for phacoemulsification cataract surgery training, which is the most common surgical technique currently being used to remove cataracts from the patient’s eyes. The procedure requires emulsifying the cloudy natural lens of the eye and restoring vision by implanting an artificial lens through a small incision. The four main procedures of cataract surgery, namely corneal incision, capsulorhexis, phacoemulsification, and intraocular lens implantation, are incorporated in the simulator for virtual surgical training by implementing several surgical techniques. The surgical activity that are applied on the anatomy of the human eye, such as incision, grasping, tearing, emulsification, rotation, and implantation, are simulated in the system by using different types of mesh modifications. A virtual reality surgical simulator is developed, and the main procedures of phacoemulsification cataract surgery are successfully simulated in the system. The simulation results of the training system show that the developed simulator is capable of generating a virtual surgical environment with faithful force feedback for medical residents and trainees to conduct their training lessons via the computer using a pair of force-feedback haptic devices. In addition, the successful simulation of the mesh modifications on the human eyeball with visual realism and faithful force feedback throughout the surgical operation shows that the developed simulator is able to serve as a virtual surgical platform for surgeons to train their surgical skills.     

虚拟手术中软组织切割模型研究进展*

虚拟手术仿真训练系统是虚拟现实的重要应用,能够克服真实传统手术中资源少、训练不方便和可重复操作性差等问题。软组织切割是虚拟手术仿真训练系统中的重要组成部分,也是手术中最常见的操作。软组织切割模型建立的质量如何,直接决定了虚拟手术仿真的精度度和仿真度。为更好地对软组织切割模型进行深入探索,分析了虚拟手术仿真中软组织切割的研究难点。针对当前十四种有代表性的切割模型进行了研究,在此基础上对这些模型的优缺点进行了比较,并对软组织切割模型的发展趋势进行了展望。     

Beyond the visuals: tactile augmentation and sensory enhancement in an arthroscopy simulator

This paper considers tactile augmentation, the addition of a physical object within a virtual environment (VE) to provide haptic feedback. The resulting mixed reality environment is limited in terms of the ease with which changes can be made to the haptic properties of objects within it. Therefore sensory enhancements or illusions that make use of visual cues to alter the perceived hardness of a physical object allowing variation in haptic properties are considered. Experimental work demonstrates that a single physical surface can be made to ‘feel’ both softer and harder than it is in reality by the accompanying visual information presented. The strong impact visual cues have on the overall perception of object hardness, indicates haptic accuracy may not be essential for a realistic virtual experience. The experimental results are related specifically to the development of a VE for surgical training; however, the conclusions drawn are broadly applicable to the simulation of touch and the understanding of haptic perception within VEs.     

Influences of haptic communication on a shared manual task

With the advent of new haptic feedback devices, researchers are giving serious consideration to the incorporation of haptic communication in collaborative virtual environments. For instance, haptic interactions based tools can be used for medical and related education whereby students can train in minimal invasive surgery using virtual reality before approaching human subjects. To design virtual environments that support haptic communication, a deeper understanding of humans′ haptic interactions is required. In this paper, human′s haptic collaboration is investigated. A collaborative virtual environment was designed to support performing a shared manual task. To evaluate this system, 60 medical students participated to an experimental study. Participants were asked to perform in dyads a needle insertion task after a training period. Results show that compared to conventional training methods, a visual-haptic training improves user′s collaborative performance. In addition, we found that haptic interaction influences the partners′ verbal communication when sharing haptic information. This indicates that the haptic communication training changes the nature of the users′ mental representations. Finally, we found that haptic interactions increased the sense of copresence in the virtual environment: haptic communication facilitates users′ collaboration in a shared manual task within a shared virtual environment. Design implications for including haptic communication in virtual environments are outlined.     

视触觉融合的增强现实三维注册方法

增强现实技术是近年来人机交互领域的研究热点.在增强现实环境下加入触觉感知,可使用户在真实场景中看到并感知到虚拟对象.为了实现增强现实环境下与虚拟对象之间更加自然的交互,提出一种视触觉融合的三维注册方法.基于图像视觉技术获得三维注册矩阵;借助空间转换关系求解出触觉空间与图像空间的转换关系;结合两者与摄像头空间的关系实现视...     

悬臂式掘进机虚拟仿真平台设计

悬臂式掘进机广泛应用于煤矿井下巷道施工,掘进机的培训包括传统的书本教学方法和基于井下实际操作的训练方法,但是由于其场地和安全的局限性,无法满足训练要求.针对这一现状,利用虚拟现实技术和交互仿真技术构建了悬臂式掘进机虚拟仿真平台.该平台采用三维建模技术,使用多边形建模方法制作了悬臂式掘进机、转载机、供电系统等三维模型;运用Unity3D引擎驱动三维模型组成的虚拟场景,采用场景优化技术实时渲染出沉浸式的虚拟场景;在脚本语言C#编程环境下实现操作流程顺序控制、操作描述、三维模型驱动等,实现悬臂式掘进机虚拟仿真培训.培训结果表明,沉浸式人机交互可达到与实物培训相类似的效果,提高使用者学习和操作悬臂式掘进机的效率.     

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。     

基于VR技术的虚拟维修仿真系统设计与应用

针对产品并行研发模式下的维修性问题,将虚拟现实技术引入到产品维修仿真中,即在计算机生成的虚拟现实环境中对产品进行维修仿真分析。文中以单通道被动立体投影系统为虚拟现实环境,以DELMIA、VRCO VisTool、CDVI、Pro/E等软件为虚拟现实软件系统,构建了一个虚拟维修系统,阐述了系统中VR外设集成、环境建模与数据转换、碰撞检测、人机工效和立体显示等关键技术。最后以某型雷达天线转台维修为例,验证了虚拟维修的有效性。     

Haptic rendering for dental training system

Immersion and interaction are two key features of virtual reality systems, which are especially important for medical applications. Based on the requirement of motor skill training in dental surgery, haptic rendering method based on triangle model is investigated in this paper. Multi-rate haptic rendering architecture is proposed to solve the contradiction between fidelity and efficiency requirements. Realtime collision detection algorithm based on spatial partition and time coherence is utilized to enable fast contact determination. Proxy-based collision response algorithm is proposed to compute surface contact point. Cutting force model based on piecewise contact transition model is proposed for dental drilling simulation during tooth preparation. Velocity-driven levels of detail haptic rendering algorithm is proposed to maintain high update rate for complex scenes with a large number of triangles. Hapticvisual collocated dental training prototype is established using half-mirror solution. Typical dental operations have been realized including dental caries exploration, detection of boundary within dental cross-section plane, and dental drilling during tooth preparation. The haptic rendering method is a fundamental technology to improve immersion and interaction of virtual reality training systems, which is useful not only in dental training, but also in other surgical training systems. Supported by National Natural Science Foundation of China (Grant Nos. 60605027, 50575011), National High-Tech Research & Development Program of China (Grant No. 2007AA01Z310)