| Along with rapid developments of the virtual reality, computer simulation, 3-D games as well as distributed platforms, computer simulation with virtual reality on a personal computer or a local network is no more adequate. People hope to implement real-time and interactive simulation of a virtual reality on the distributed complex Internet to achieve sure real feelings.Synchronization between servers and clients in complex distributed environment is a key design issue as well as a difficult point for implementing better real-time and interactive simulation to achieve the real feelings. It is very important to construct a highly efficient network synchronization model for enhancing simulating quality and efficiency.The classical synchronous schemes are server-oriented architecture. Operations in clients are verified by the server, and then the server sends synchronization messages to corresponding clients to achieve all system synchronization. The simulation system is all synchronized by a system server timer. Such a traditional synchronization method has been verified as a robust, complete and easy implemented scheme. However as scale of three dimensions panorama simulation becomes very big, more and more clients are engaged and expectation of truly virtual reality becomes more and more aggressive, the classical synchronization model can not satisfy the real time simulation requirement.Based on above consideration a client-oriented network synchronization model has been proposed in the thesis. This new synchronization model adopts more reasonable method to determine synchronous scope, lets the clients become leading role in synchronization, perform most synchronization operations and employ the agile and fast UDP protocol to transfer synchronous massage. In this model the synchronous work load of the server is very light, which is just in charge of synchronous scope verification and only sends out synchronous correction messages and/or synchronous scope updating messages.Since the proposed network synchronous model has a client-oriented property, but communication statuses of engaged clients are dynamically changeable, so the UDP protocol is perfectly served as the basic communication protocol in the proposed synchronous model. Variable synchronous streams aroused by active clients are suitable for the agile and fast UDP protocol, but not for the static TCP protocol. Meanwhile the ports sharing ability of the UDP is a perfect solution for maintenance of synchronous scopes in the proposed new synchronous model.It has been proved in the thesis that the new proposed network synchronous model has higher communication efficiency, sharply reduces server communication loads, hence can support multiple number of users in the same network bandwidth of simulation systems.The thesis is composed as followings: The chapterl introduces backgrounds, purpose and significance of the thesis;chapter2 discusses basic principles of network communication, and focuses on the TCP/IP reference model, Windows Socket Programming, as well as the MFC multi-thread programming;chapter3 analyses the classical network synchronous models and discusses several traditional synchronous algorithms;chapter4 discusses in detail the new proposed client-oriented network synchronization model, designs corresponding synchronization algorithms, and has made comparisons of the new model and old model in the synchronous scope as well as communication quantity on the server;Chapter5 analyses the transport protocol of the new proposed client-oriented network synchronization model;Finally Chapter6 gives a conclusion for whole thesis and makes an expectation for next stage of this research.This work is supported by Natural Science Foundation of China (Grant numbers: NSFC 60073057 and 60173046), Innovation Fund for Technology Based Firms of MOST, China (Ministry of Science and Technology of the PRC), and part of this research was done during visits of author to the University of Greenwich supported by the UK EPSRC grant GR/T10183/01. |
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