nbul 2004 
    
RESEARCH ON VISUALIZATION TECHNOLOGY OF CYBERCITY 3D SCENE 
Zhou Yang, Xu Qing, Lan Chaozheng , TanBing 
(Institute of Surveying and Mapping, ZhengZhou 450052, China) 
zhouyang@chxy.com 
PS WG V/6 
Visualization and Animation 
Key Words:, GIS, Analysis, Modelling, Visualization, Data Structures, DEM/DTM, Texture, System 
Abstract: 
3D visualization is a Key Technology in CyberCity. It has been applied in many fields. In this paper, we discussed and studied several 
key techniques of 3D visualization in CyberC ity. These key techniques contain Oriented Object 3D Data Model, Advanced Modeling 
Techniques which contain Particle System and Billboard, 3D Scene Accelerate Rendering Techniques, Information Inquire techniques 
in 3D scene and so on. The 3D Scene Accelerate Rendering Techniques contain Object Culling, Back Face Culling and LOD (level of 
detail) technique. Based on these techniques, we designed and implemented an advanced 3D Rendering Engine. At the end of paper, 
we give some results created by the 3D Rendering Engine. The results show that the 3D engine can render highly reality 3D scene and 
user can obtain highly immersion by rambling in 3D scene and inquiring information based on database. 
| Introduction 
The conception of CyberCity is derived from digital earth and is 
the important part of digital earth. As a new technique, 
CyberCity can be regarded as expansion and development from 
CIS. By the studying Visualization Technology of CyberCity 
3D scene, which apply the 3D Visualization technique in 
construction of CyberCity, we can change the description of city 
scene’s actuality and programming in terms of 2D map and 3D 
solid model into in terms of 3D space representation of 
computer. 
We think there are mainly several key techniques in CyberCity 
3D scene Visualization Technology. They are as follows: 
1) Data structures: Data structures are a base of representation 
for a solid object. À satisfactory data structure described a 
solid model may even make it possible to generate 
instructions automatically for —computer-controlled 
machine tools to create that object. So whether the data 
structure described a solid model is advanced determine 
the performance of a 3D engine. 
2) Large dataset Accelerate Rendering technique: Highly 
detailed geometric models are necessary to satisfy a 
growing expectation for realism in Cybercity 3D scene 
rendering. But the computer graphic hardware' developing 
is limited and a large dataset 3D scene makes real time 
rendering difficult. To try to attain real time frame rate, we 
must take some strategy to accelerate the 3D scene 
rendering. Currently, the accelerate Rendering technique 
include manage disk paging of geometry and texture, level 
of detail (LOD) selection for texture blocks, LOD for 
triangle geometry, culling to the view frustum, and triangle 
  
[Point2 | Line2 [Area2 | 
A Polymerize 
  
—» Derive 
stripping and so on. 
3) Advanced modeling: Advanced modeling can describe 
many natural phenomena efficiently. For example, fog, 
smoke, burst etc are efficiently represented by advanced 
modeling and vegetation can be rendering by Billboard. 
4) Information Inquire and analysis in 3D scene. Information 
inquire and analysis based database in 3D scene is one of 
key technique in 3D GIS and it is the character differed 
from the general software of 3D rendering. User can gain 
more interest information by the function of inquire and 
analysis. 
In this paper, we discus and research these techniques Based on 
these researches, we design and implement an advanced 3D 
Rendering Engine PowerCity3D. The PowerCity3D is applied 
in many fields and get some good results. At the end of this 
paper, we give some examples created by the 3D Rendering 
Engine and draw some conclusions. 
2 Space Object Reconstruction 
2.1 Oriented Object Data Structure 
The space object’ 3D Modeling is an important technique to 
Visualization in CyberCity 3D scene. In order to reconstruct the 
object quickly and reliably, we must design an advanced data 
model. Because of the variety of space object, we use Oriented 
Object’s idea to design space object’ data structure. 
In order to adapt to city 3D scene’s rendering and information 
inquire and analysis, we use the follows space object data model 
to describe the city object: 
Object 
    
    
Object3D 
  
  
  
Model3D Model3D 
Fig.1 Oriented Object’s data structure 
647