分散式多人互動虛擬實境系統之研究

Abstract

隨著近幾年來圖形加速卡的進步，精緻且複雜的三維虛擬實境場景即時著色的速度已逐漸讓人滿意。網路頻寬的大幅提昇，除了可以讓使用者在需要瀏覽場景時即時下載，還可以達到多人參與瀏覽，以及動態修改場景以達到互動的目的。 要製作這樣一套網路虛擬實境系統，並包含多人互動的功能，可以考慮使用標準的虛擬實境模擬語言 (VRML) 來實作。目前的VRML版本僅提供立體物件的定義及單人環境下與現存物體的互動功能，至於網路多人互動的部分則付之闕如。幸好它提供了一套外部程式控制的方法，讓我們可以使用外在的Java程式建立網路連線，再經由與伺服器的訊息交換做出本地端對應場景的改變，以達到多人互動的功能。 本論文的目的，在於研究一套架構於VRML-JAVA-EAI (External Authoring Interface)的多人互動虛擬實境系統，並根據此架構成功地實作出一套系統以供實際應用的參考。

With the great improvement of network speed, computer CPU power and graphical capability, it is gradually becoming possible to develop virtual reality systems participated by multi-users via networks. Virtual Reality Modeling Language (VRML) is a standard for modeling 3D virtual worlds under WWW; however, the current version of VRML does not support interaction between multiple users. To overcome this shortcoming of VRML, we can employ JAVA to enable network communication among participant computers and External Authoring Interface (EAI) to facilitate control over the local scene data of a virtual environment. In this paper, we propose an architecture for a client-server multi-user virtual reality system that is realized by VRML, JAVA, and EAI. In this paper, we refine the PDUs proposed in DIS to encapsulate messages transferred in our system. A pre-buffering method and dead reckoning are leveraged to overcome the disadvantages of TCP. Finally, the results and demonstration of our system are also introduced in this paper.