Some key technologies on how to build large-scale virtual tourism systssems comprehensively on Web browsers and mobiles were analyzed and the current R&D status on Web3D virtual tourism was surveyed insightfully. Then, some methods were summarized, including 3D trees or plants modeling, 3D architectural modeling, 3D Virtual Human behavior modeling, virtual agents path planning, collision detection and progressive transmission strategy suitable for developing large scale Web3D tourism scenarios. Also, some bottleneck problems of Web3D virtual tourism system were investigated. At the same time, the lightweight 3D engine, the lightweight 3D modeling, the lightweight 3D streaming and P2P based progressive transmission of huge Web3D tourism contents would become much helpful to breakthrough those bottlenecks of Web3D tourism systems were pointed out. In addition, all kinds of Web3D engines in terms of lightweight, realism and efficiency that would be a good reference for developers to choose during various applications were compared comprehensively. Finally, the prospect of future investigation of Web3D tourism system is presented, which will be going on in terms of four characteristics lightweight, high-speed, realism, beauty.
