PHOTOREALISTIC BUILDING MODELING AND VISUALIZA TION 
IN 3-D GEOSPATIAL INFORMATION SYSTEM 
Yonghak Song 
Jie Shan 
Geomatics Engineering, School of Civil Engineering, Purdue University 
550 Stadium Mall Drive, West Lafayette, IN 47907-2051, USA — (song10, jshan)@ecn.purdue.edu 
TS 1 YF 
KEY WORDS: Photorealistic, 3-D, Geographic information systems, Visualization, Building modeling, Texture mapping. 
ABSTRACT: 
Despite geospatial information systems are widely used in many different fields as a powerful tool for spatial analysis and decision- 
making, their capabilities to handle realistic 3-D urban environment are very limited. The objective of this work is to integrate the 
recent developments in 3-D modeling and visualization into GIS to enhance its 3-D capabilities. To achieve a photorealistic view, 
building models are collected from a pair of aerial stereo images. Roof and wall textures are respectively obtained from ortho- 
rectified aerial image and ground photography. This study is implemented by using ArcGIS as the work platform and ArcObjects 
and Visual Basic as development tools. Presented in this paper are 3-D geometric modeling and its data structure, texture creation 
and its association with the geometric model. As the results, photorealistic views of Purdue University campus are created and 
rendered with ArcScene. 
1. INTRODUCTION 
Three-dimensional (3-D) photorealistic visualization is one of 
the most important functionalities in geospatial information 
system (GIS). Such 3-D photorealistic visualization is able to 
provide geospatial information for easy human perception. It is 
helpful in geospatial information interpretation and the decision 
making process (El-Hakim, 1998). Through the past years, 
many successful models are developed to represent typical 
geospatial features such as terrain, road, water body, vegetation 
and many others. However, these are primarily 2- D or 2.5-D in 
nature. 3-D features like buildings may not be represented well 
by existing 2-D data structures and tools (Braun, et, al, 1995). 
An effective geometric modeling approach is needed to model 
the spatial location and the topology of buildings. In addition, 
this model should also be extended to include other information 
for buildings, such as attributes and image textures for query 
and visualization purpose. Using image as texture will not only 
increase the realism of the model but also enable the viewing of 
details. It improves the interpretability; in other words, the 
relationship between objects can be perceived easily and 
reliably when photorealistic models are used in visualization 
(Varshosaz, 2003). Although there are a lot of advanced studies 
in computer graphics and commercial products in computer 
industry, they do not typically handle geospatial information 
and can not be easily integrated into existing GIS packages to 
enhance its visualization capability, which is becoming a 
demanding functionality in processing 3-D geospatial 
information. On the other hand, GIS is a popular and standard 
system with powerful 2-D spatial analysis capabilities. 
However, its 3-D functionality is very limited where 
photorealistic visualization is certainly a very useful addition. 
The objective of this study is therefore to develop a 3-D data 
structure, incorporate it into GIS and implement it for 3-D 
photorealistic visualization to enhance current GIS capabilities. 
We first discuss the suitability of the geometric building models 
to be used for 3-D modeling and visualization. Then, a 3-D 
geometric approach for building modeling is proposed. Under 
this model, a building is composed of two parts; roof and 
(vertical) walls. To achieve photorealistic visualization, these 3- 
D geometric models are extended through texture mapping with 
aerial photos for roof and ground photos for walls. In addition, 
the algorithm associating geometric models with corresponding 
texture images is discussed. After photorealistic building model 
and appearance are achieved through modeling and texturing, 
we discuss how to integrate 3D building model with other 
geospatial data to generate the entire urban model. These 
developments are integrated into ArcGIS package to enhance its 
3-D visualization capabilities. Precise texture generation and 
automatic texture mapping are discussed as an important 
procedure to achieve high quality visualization effect. To 
demonstrate and evaluate our developments, photorealistic 
virtual campus models over Purdue University are presented. 
2. GEOMETRIC BUILDING MODELS 
Most GIS packages are designed for modeling terrain and other 
2-D features. It is therefore not suitable for building modelling. 
In such data models, the 3-rd dimension usually is obtained by 
vertically extruding the 2-D footprint. In this approach, only 
horizontally flat roofs or piecewise horizontally flat roofs can 
be modeled. Hence we need a true 3-D model and incorporate it 
into GIS. 
There are many methods to model 3-D objects, such as wire- 
frame model, surface model, and solid model. Usually GIS 
packages use surface model and solid model is widely used in 
the field of CAD (Computer Aided Design) and computer 
graphics. Recent trend is to adopt the solid model to represent 
buildings under CAD environment. The solid model such as 
CSG (Constructive Solid Geometry) and B-rep (Boundary 
representation) are very suitable to represent objects with 
complex geometry and their physical characteristics. However, 
it requires large memory and is relatively slow in displaying 
because of the complex data structures and evaluation of the 
data during rendering. Figure 1 shows the wire frame model and 
the surface model for the same group of buildings. In the wire 
frame model, edges are formed from vertices and no explicit 
information exists about faces of the object. The dot symbol in