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To allow geographical dispersed engineers to perform an assembly task together, a Virtual Environment for Collaborative Assembly (VECA) has been developed to build a typical collaborative virtual assembly system. This presents the key parts of VECA, such as system architecture, HLA-based (High Level Architecture) communication and collaboration, motion guidance based on collision detection and assembly constraints recognition, data translation from CAD to virtual environment, reference resolution in multimodal interaction. 1. Introduction Virtual reality (VR) is a technology which is often regarded as a natural extension to 3D computer graphics with advanced input and output devices. Now VR has matured enough to warrant serious engineering applications [1]. As one of the important application domains of VR, virtual assembly (VA) fulfills design flexibility by replacing physical objects with the virtual representation of machinery parts and providing advanced user interfaces for users to design and generate product prototypes [2]. VA can evaluate and analyze product assembly and disassembly during the product design stage with the goal of reducing assembly costs, improving quality and shortening time to market [3]. With the distributed fashion of companies and research organizations, many design, assembly, manufacture, analysis works require the collaboration of geographical dispersed engineers. Collaborative This paper is supported by A.S.T. Fund (VEADAM ), National Natural Science Foundation of China (60503066), National Research Fund (51404040305HK01015), China Education and Research Grid (ChinaGrid) Program (CG2003-GA004), National 863 Program (2004AA104280) & (SIMBRIDGE). virtual environment (CVE) is a computer system that allows remote users to work together in a shared virtual reality space [4]. As an important category of Computer-Supported Cooperative Work (CSCW) and VR, CVE systems have been applied to military training, telepresence, collaborative design and engineering, distance training, entertainment, and many other personal and industrial applications [5]. Because of the advantages of CVE and the actual requirement of industry, collaborative virtual assembly (CVA) is becoming one of research emphases of VA. There have been many research efforts to develop virtual assembly systems [6][7][8]. A representative system is Virtual Assembly Design Environment (VADE) [9] which allows engineers to evaluate, analyze, and plan the assembly of mechanical systems. VADE simulates inter-part interaction for planar and axisymmetric parts using constrained motions along axes/planes which are obtained from the parametric CAD system. In this system, direct interaction is supported through a CyberGlove. In the field of CVA, several systems have been created. For example, National Center for Supercomputing Applications (NCSA) and Germany’s National Research Center for Information Technology (GMD) developed a collaborative virtual prototyping system over ATM network [10]. The system integrated real-time video and audio transmissions let engineers see other participants in a shared virtual environment at each remote site’s viewpoint position and orientation. Jianzhong Mo et al. developed a virtual-reality-based software tool- Motive本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。