数字城市有广义和狭义之分，本文所指的数字城市是狭义的概念，可以理解为一个虚拟化的数字城市应用系统，它是虚拟现实技术应用的一个主要方面。狭义的数字城市在城市规划、建筑规划、交通控制等领域有着广泛的应用，因而相关技术在国内外学术界一直是被关注和研究的热点。 在数字城市建设过程中，建模是非常繁杂的一项工作，需要耗费大量的人力物力资源。为了解决传统建模软件速度和效率的问题，本文通过对建模技术的研究，提出了一种基于DLG的建模方法。该方法通过对建筑物进行拆分，抽象出有限的几种模型元，通过对有限的几种模型元进行建模，从而组合成各种各样的建筑物模型。该方法设计了一种使用XML进行模型数据传递的架构，实现了批量模型生成。与此同时开发了可以在CAD环境下对DLG数字线划图进行编辑和编码的辅助建模模块，并开发了模型生成模块用于模型生成。研究了四元数及其插值算法，并将其应用于模型旋转,最终实现了模型的光滑旋转。研究了立体技术，使用了一种基于被动立体的双通道立体投影方案，实现了场景的三维立体显示。除此之外，本文还对数字城市漫游系统的框架进行了总体设计；对场景漫游器进行了研究，实现了方便的场景漫游操作；实现了场景求交的基本功能；研究了粒子系统，在此基础上实现了数字城市虚拟环境中的雨、雪效果；使用Billboard技术实现了树的建模；实现了模型的贴图功能。 实践证明，本文提出的建模方法能够快速有效的进行模型的批量生成，并保证了模型的三维空间精度，同时支持具有一定细节层次的建模。使用四元数球面插值算法结合TrackBall原理实现了模型的光滑旋转，达到了理想效果。开发的系统有助于数字城市的规划和管理，为数字校园、数字小区的研究与建立起到了示范作用。

Digital city has a broad and a narrow notion, in this paper, we refers to the narrow one and can be interpreted as a digital city virtualization application system, it’s a specific application of virtual reality.Digital city have been widely used in the urban planning,construction planning,traffic controlling.Technology about digital city in national and international academic region have been concerned. During the construction proccess of digital city,modeling is an extremly complicated job,and need a lot of manpower, material resources.To solve the traditional modeling software speed and efficiency problem, after the research on modeling method,in this papaer we present a method of modeling based on DLG. In this method,we splited buildings into pieces and abstracted a number of model primitives.After modeling for these primitives,then we can compose them into all kinds of building models.This method design a kind of architect which use XML for the transportation of model data,and then realize the batch modeling.At the same time we developed a modeling module and an auxiliary modeling module which can run under the CAD enviroment for editing and coding the DLG. Study on the quaternion and quaternion interpolation algorithm,then apply this algorithm on the model rotation,and realized the smooth raotation of the model ; Study on the stereovision technology,apply a kind of passitive stereo projection scheme and realize the steorovision of the visual scene.Beside this,we design the overall framework of the digital city roaming system; Study on the scene roaming manipultor and realize the convinience scene roaming operation; Realize the fundamental interactive function;Study on the partical system,and realize the snowing and raining effect in vitual system;Realize the tree modling by using billborad technology;Realize the texture mapping function of the system. Practice proves that this proposed modeling method is a rapid and effective way for batch modeling, and ensure the precision of the models in 3D space, and also support for modeling in detail of the building.With the theory of TrackBall, quaternion interpolation method realized the smooth interpolation of the model rotation,and reach an ideal effect.Finally, the developed system is helpful for city planning and management and set up an example for the research on digital campuse and digital community.