Research And Implementation On Some Key Technology Of Digital City Roaming System

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.