Collision detection methodologies for rigid body assembly in a virtual environment

In this paper, a simulated three-dimensional virtual environment is created with a virtual 3D track ball for virtual object control. We propose a new technique called HV Partition to detect accurate collision in the assembly of two polyhedral solids in virtual simulation. This is a solid interference detection methodology achieved by automatically partitioning the object into smaller solid boxes. An important advantage of this methodology compared with other approaches is that it can deal with non-convex objects. This means that mechanical components, represented by non-convex polyhedra, traversing any degree of freedom, can be used in this virtual environment. Using this HV Partition method, the precise interference between two polyhedral solid objects can be found. The HV Partition methodology is applied following initial approximate collision detection using traditional bounding box and bounding sphere methods. The smaller the number of smaller boxes, the quicker is the performance of the collision algorithm. An optimal partition method is also given to reduce the number of smaller boxes in an object.     

基于VRML和Java的虚拟装配技术

对虚拟装配技术理论进行研究,应用三维形体空间坐标变换原理,利用虚拟现实建模语言（Virtual Reality Modeling Language,VRML）,结合Java语言,在Cortona浏览器的基础上构建可视的交互虚拟装配环境,并给出虚拟装配过程的实例．     

Integration of manufacturing services into virtual environments over the internet

Virtual reality (VR) is a rapidly developing technology that has a wide spectrum of industrial and commercial applications. Networked (distributed or shared) virtual environments (VE) are of growing interest to modern manufacturing industry; a dominating use of networked virtual manufacturing environments (VMEs) is on-line visualisation and collaborative control of 3D information. This has to be supported by real-time data transfer. To meet a broad range of common requirements for Internet-based VE communications, particularly for virtual manufacturing and collaborative design and control, this paper presents a networked virtual environment system that is designed to support networked virtual design and manufacturing. The system is implemented with manufacturing message specification (MMS) standards so as to integrate a range of manufacturing services into networked VEs over the Internet.     

Construction of feature-matching perception in virtual assembly

An important characteristic of virtual assembly is interaction.Traditional direct manipulation in virtual assembly relies on dynamic collision detection,which is very time-consuming and even impossible in desktop virtual assembly environment.Feature-matching is a critical process in harmonious virtual assembly,and is the premise of assembly constraint sensing.This paper puts forward an active object-based feature-matching perception mechanism and a feature-matching interactive computing process,both of which make the direct manipulation in virtual assembly break away from collision detection.They also help to enhance virtual environment understandability of user intention and promote interaction performance.Experimentl results show that this perception mechanism can ensure that users achieve real-time direct manipulation in desktop virtual environment.     

面向虚拟装配的装配建模及其重构

装配建模是进行虚拟装配的前提和基础,决定着虚拟装配实施的质量和效率。针对虚拟装配中装配建模问题,介绍一种多视图层次化的装配模型,给出了模型的信息组成和信息来源,并很好地解决了在此模型基础上的重构问题。     

精馏系统的虚拟装配技术研究

将虚拟装配技术引入化工流程中,对可视化设计化工流程、培训工人操作技能以及化工厂的数字化建设具有很大的应用价值。通过分析精馏系统,搭建了可视化装配平台。根据装配约束条件建立了可装配设备模型。提出了"1+1"和"1+n"普遍化的装配方法,实现了装配复杂精馏系统。通过输出装配信息,获取精馏系统装配过程中的装配方式和装配序列,验证装配操作的正确性。装配测试表明装配方法正确可行,其真实性、准确性和有效性满足了精馏系统虚拟装配的要求,实现了自由选择设备装配所需的精馏系统。系统可扩展性强,通过添加其它单元设备,可以实现所有化工流程的虚拟装配。     

基于网格的分布式虚拟环境仿真

针对传统分布式虚拟环境仿真的不足,将网格计算技术引入到分布式虚拟环境仿真中。提出了基于网格的分布式虚拟环境仿真分层体系结构。该体系结构自底向上依次为网格节点、高性能通信系统、数据存储系统、计算系统、资源管理系统、仿真应用系统,并通过网格门户提供统一的仿真应用系统入口。建立了一个基于该体系结构的原型系统并进行了仿真测试。仿真结果表明所提出的体系结构设计满足虚拟环境仿真实时性、稳定性和可靠性的要求。     

一种虚拟室内场景调度策略与碰撞处理方法

文章实现了一种以门区为控制域的复杂虚拟室内场景实时三维漫游的调度策略,给出了一种基于二维判别图处理虚拟室内环境中碰撞检测与碰撞响应的新方法。     

虚拟内窥镜系统的关键技术分析

概述了虚拟内窥镜的基本原理、优点及发展现状;针对目前虚拟内窥镜系统存在的问题,结合各种处理算法,以其实现过程为主线,具体分析了虚拟内窥镜系统的几个关键性技术,重点讨论了路径规划、实时绘制及导航的研究内容;最后对虚拟内窥镜的研究特点和趋势作了总结。     

Embodiment analytics of practicing teachers in a virtual immersive environment

Interactive training environments typically include feedback mechanisms designed to help trainees improve their performance through either guided or self‐reflection. In this context, trainees are candidate teachers who need to hone their social skills for their future classroom. We chose an interactive virtual training system as the basic research environment to investigate the embodiment of the trainees. Using tracking sensors and improvements for existing gesture recognition utilities, we created a gesture database and used it for the implementation of our real‐time feedback application. We also investigated multiple modalities of feedback including visual and haptics. This paper describes the context in which the utilities have been developed, the importance of recognizing nonverbal communication in the teaching context, the means of providing automated feedback associated with nonverbal messaging, and a series of preliminary studies developed to inform the research. Results from the conducted studies indicate the positive impact of the proposed feedback application.     

Networked multiplayer cooperative interaction using decoupled motion control method in a shared virtual environment with haptic,visual and movement feedback

This paper focuses on multiplayer cooperative interaction in a shared haptic environment based on a local area network. Decoupled motion control, which allows one user to manipulate a haptic interface to control only one‐dimensional movement of an avatar, is presented as a new type haptic‐based cooperation among multiple users. Users respectively move an avatar along one coordinate axis so that the motion of the avatar is the synthesis of movements along all axes. It is different from previous haptic cooperation where all users can apply forces on an avatar along any direction to move it, the motion of which completely depends on the resultant force. A novel concept of movement feedback is put forward where one user can sense other users’ hand motions through his or her own haptic interface. The concept can also be explained wherein one person who is required to move a virtual object along only one axis can also feel the motions of the virtual object along other axes. Movement feedback, which is a feeling of motion, differs from force feedback, such as gravity, collision force and resistance. A spring‐damper force model is proposed for the computation of motion feedback to implement movement transmission among users through haptic devices. Experimental results validate that movement feedback is beneficial for performance enhancement of such kind of haptic‐based cooperation, and the effect of movement feedback in performance improvement is also evaluated by all subjects.Copyright © 2012 John Wiley & Sons, Ltd.     

Multi-agent based virtual environment and its application

Most existing researches on virtual environment in mining industry are mainly concentrated on the geometric presentation to create immersive experiences and little attention has been paid on system modeling and formal specification. This paper focuses on modeling methodology of coalmine virtual environment （CMVE） and its application in underground mine safety. A hierarchical architecture model for CVME was present based on multi-agent technology. The proposed model consists of hardware, network and operating system layer, geometric and physical layer, multi-agent layer and man-machine interface layer, and has distinctive features such as reusability, reconfigurability, scalability, intelligence and interactivity. To make multi-agent based CMVE framework more precise, related concepts and agent properties were formally defined. In addition, the design method of typical agent was also discussed and a virtual miner model was built. Finally, an application system for behavior simulation of underground mine safety was introduced. The case system achieves interactive control of virtual environment and fully indicates the capability of producing effective virtual environment for behavior simulation of underground mine safety.     

VRML 虚拟现实网络互动仿真装配平台的研究

在计算机上实现了虚拟装配的流程以及运用VRML 创建可视化的三维虚 拟场景,提出了一种基于VRML 和Java 的虚拟现实构建方法,以增强VRML 虚拟场景与外 界的交互性,并通过实例提出了创建网络虚拟装配交互仿真的具体方案。该方法不仅可用于 演示网络环境下的可视化装配,也适用于基于VRML 的其它领域科学可视化。     

Learning effectiveness in a Web-based virtual learning environment: a learner control perspective

Web-based technology has a dramatic impact on learning and teaching. A framework that delineates the relationships between learner control and learning effectiveness is absent. This study aims to fill this void. Our work focuses on the effectiveness of a technology-mediated virtual learning environment (TVLE) in the context of basic information technology skills training. Grounded in the technology-mediated learning literature, this study presents a framework that addresses the relationship between the learner control and learning effectiveness, which contains four categories: learning achievement, self-efficacy, satisfaction, and learning climate. In order to compare the learning effectiveness under traditional classroom and TVLE, we conducted a field experiment. Data were collected from a junior high school of Taiwan. A total of 210 usable responses were analysed. We identified four results from this study. (1) Students in the TVLE environment achieve better learning performance than their counterparts in the traditional environment; (2) Students in the TVLE environment report higher levels of computer self-efficacy than their counterparts in the traditional environment; (3) Students in the TVLE environment report higher levels of satisfaction than students in the traditional environment; and (4) Students in the TVLE environment report higher levels of learning climate than their counterparts in the traditional environment. The implications of this study are discussed, and further research directions are proposed.     

Agent技术在虚拟企业创建过程中的应用研究

虚拟企业（virtual enterprise，VE）被认为是21世纪最有竞争力的企业运行模式，它面向全球范围的企业资源，通过构建VE的联盟之间的快速重组，实现联盟企业之间的敏捷化和柔性化。如何选择伙伴企业，则是VE创建过程中的关键。文章首先采用了分布式对象技术以支持VE创建时的需要；然后提取了用于伙伴企业选择的Agent基本属性；规划了伙伴企业选择过程；最后用多Agent技术为VE构建一个支持动态联盟的多Agent远程制造系统。     

基于语义虚拟环境的虚拟人动画研究与实现*

现有虚拟环境建模（如VRML/X3D）主要集中在几何图形的描述,所显示的虚拟场景对于人是可理解的,但对于计算机是不可理解的,因而难以作有意义的自动处理。基于语义Web设计了一个语义虚拟环境（主要包括语义虚拟场景和语义虚拟人）,并设计了基于语义虚拟环境的虚拟人动画引擎。语义虚拟环境使得计算机能够理解和自动处理虚拟环境的语义信息,并且使得虚拟环境系统具有可重用性、可扩展性和可集成性。最后,在语义虚拟环境和虚拟人动画引擎的基础上开发了一个办公室场景中智能虚拟人行动推理的系统,取得了很好的效果。     

虚拟装配中快速碰撞检测算法的研究与实现

针对虚拟装配中碰撞检测的特殊要求，提出了一种基于包围盒与空间剖分法的两级碰撞检测算法HSDHBB。该算法首先用空间剖分法找出潜在的相交区域，然后用包围盒求得碰撞的三角面片对和精确的碰撞点。给出了层次包围盒树的构造方法和空间网格的剖分方法，在空间剖分中采用哈希表的数据结构加快检索速度。最后，在CATIA环境中实现了该算法，结果表明该算法能够满足虚拟装配系统的实时性和精确性的要求。     

基于Web的虚拟旅游环境的开发及其关键技术*

首先介绍了虚拟旅游的基本概念、研究意义、开发模式和主流开发平台,进而针对虚拟旅游的关键技术作了综述性研究,最后对虚拟旅游将来的开发方向进行了展望性研究。     

Internet-based virtual computing environment(iVCE):Concepts and architecture

Resources over Internet have such intrinsic characteristics as growth, autonomy and diversity, which have brought many challenges to the efficient sharing and comprehensive utilization of these resources. This paper presents a novel approach for the construction of the Internet-based Virtual Computing Environment (iVCE), whose sig- nificant mechanisms are on-demand aggregation and autonomic collaboration. The iVCE is built on the open infrastructure of the Internet and provides harmonious, transparent and integrated services for end-users and applications. The concept of iVCE is presented and its architectural framework is described by introducing three core concepts, i.e., autonomic element, virtual commonwealth and virtual executor. Then the connotations, functions and related key technologies of each components of the architecture are deeply analyzed with a case study, iVCE for Memory.