【摘要】 漫游飞行在数字地球、虚拟现实和仿真等领域有着广泛的应用。以往的研究多集中于客户机/服务器(client/server,C/S)结构的桌面端应用程序,本文以浏览器/服务器(browser/server,B/S)结构下的Web端开源三维地理框架Cesium为基础构建虚拟地球,设计了三种不同的漫游算法:常规漫游算法、回调函数漫游算法、拉格朗日插值漫游算法,并在地球表面成功加载了重庆市主城区的倾斜摄影模型以实现漫游飞行功能,从帧率(frames per second,FPS)和网络延迟(network latency,NL)两方面对比分析三种算法的有效性。结果表明,常规漫游算法、回调函数漫游算法、拉格朗日插值漫游算法前50 s的平均FPS分别为70、74、80 Hz,平均NL分别为14.145、13.166、12.419 ms。就FPS而言,回调函数漫游算法较常规漫游算法提升了5.714%,拉格朗日插值漫游算法较常规漫游算法提升了14.286%。就NL而言,回调函数漫游算法较常规漫游算法缩短了6.921%,拉格朗日插值漫游算法较常规漫游算法缩短了12.202%。总体而言,算法运行效率从大到小最终排序为:拉格朗日插值漫游算法、回调函数漫游算法、常规漫游算法,即在漫游飞行过程中,回调函数漫游算法、拉格朗日插值漫游算法较常规漫游算法有一定的提升,拉格朗日插值漫游算法可实现更高效、流畅的渲染效果。更多还原

【Abstract】 The roaming function is widely used in the fields of digital earth,virtual reality and simulation.Previous researches mostly focused on desktop applications under client/server(C/S)structure.This paper constructs a virtual Earth based on Cesium,an open-source 3D geography framework on the Web side under browser/server(B/S) structure and designs three different roaming algorithms:conventional algorithm,callback function algorithm and Lagrange interpolation algorithm.Then,the tilting photography model of downtown Chongqing was successfully loaded on the virtual Earth’s surface to realize the roaming functions of the three different algorithms.Finally,the effectiveness of the three algorithms was compared in terms of frames per second(FPS) and network latency(NL).The results show that the average FPS in the first 50 s for conventional algorithm,callback function algorithm and Lagrange interpolation algorithm are 70,74 and 80 Hz,respectively;The average NL in the first 50 s for conventional algorithm,callback function algorithm and Lagrange interpolation algorithm are 14.145,13.166 and 12.419 ms, respectively.In terms of FPS,callback function algorithm is 5.714% higher than conventional algorithm,while Lagrange interpolation algorithm is 14.286% higher than conventional algorithm.In terms of NL,callback function algorithm is 6.921%shorter than conventional algorithm,while Lagrange interpolation algorithm is 12.202% shorter than conventional algorithm.Overall,the final order of the three algorithms’ running efficiency from largest to smallest is:Lagrange interpolation algorithm,callback function algorithm,and conventional algorithm.Namely,callback function algorithm and Lagrange interpolation algorithm have certain improvements compared with conventional algorithm in the process of roaming,and Lagrange interpolation algorithm can achieve the most efficient and smooth operation and rendering effects.更多还原