PHOTOREALISTIC TERRAIN VISUALIZATION USING METHODS 
OF 3D-COMPUTER-GRAPHICS AND DIGITAL PHOTOGRAMMETRY 
R. Würländer!, M. Gruber?, H. Mayer! 
! Lehrstuhl für Photogrammetrie und Fernerkundung 
Technische Universität München 
Arcisstr. 21, D-80333 München 
Tel: +49-89-2892-2671; Fax: + 49-89-2809573 
E-mail: {roland,helmut} @photo.verm.tu-muenchen.de 
?Institut für Computerunterstützte Geometrie und Graphik 
Technische Universitát Graz 
Münzgrabenstr. 11, A-8010 Graz 
Tel: + 43-316-8735011; Fax: + 43-316-8735050 
E-mail: gruber@icg.tu-graz.ac.at 
Commission IV, Working group 4 
KEY WORDS: Visualization, Vegetation, 3D Computer Graphics, Digital Photogrammetry, DEM, Orthoimage, 
Planning, Texture Mapping 
ABSTRACT: 
Photorealistic, i.e. highly sophisticated visualization of the terrain is an important tool for flight simulation or, like in this 
paper, for the evaluation of changes resulting from planning for land consolidation or afforestation in rural areas. Basic 
input components for the visualization of these areas are land use data from a geographic information system (GIS), 
information about the terrain surface given by a digital elevation model (DEM), as well as aerial and terrestrial photographs. 
Mapping digital orthoimages as texture onto the terrain surface is a first step towards photorealism. A new approach is 
proposed which is based on the replacement of unfavourable effects like shadows, displacements or occlusions caused by 
three-dimensional (3D) objects in the orthoimage by information from other images or from adjacent regions employing 
methods of digital photogrammetry. Using the resulting improved orthoimage together with methods of 3D computer 
graphics for the modeling and rendering of the 3D objects leads to highly realistic visualizations of the scene. 
1. INTRODUCTION 
Photorealistic visualization of the terrain by means of me- 
thods from 3D computer graphics is used in many discipli- 
nes (cf. Foley et al, 1990, for an overview). It is an important 
tool for flight or battlefield simulation, the planning of roads 
or buildings and also in the movie industry, to mention only 
a few. The application more closely examined in this paper 
is the visualization of changes within rural landscapes re- 
sulting from plannings for land consolidation or afforesta- 
tion. It can be used to evaluate the plannings as objective as 
possible as well as to promote the results in the public. 
Most of the disciplines mentioned above aim at highly 
realistic landscape visualization in real-time. Until now 
real-time is not possible for photorealistic presentation of 
existing landscapes, but it can be assumed that future gene- 
rations of high-end graphical workstations will be able to 
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achieve simultaneously the goals photorealistic presentati- 
on and real-time. 
Up to now different kinds of simplifications are necessary. 
If the goal real-time has to be met, e.g. for flight simulation, 
the geometric and radiometric modeling can not be done as 
accurately as necessary for highly realistic visualizations. If 
the goal photorealistic presentation is more important, e.g. 
in movie industry, real-time effects only can be achieved 
using pre-calculated views. This means that animation is 
possible, but real-time calculation of the views is not. 
When methods of computer graphics are used for visual 
interpretation of planning tasks for rural areas, photorea- 
listic representations are demanded. Real-time computing, 
. however, is not an important issue. 
The paper is organized as follows. In section 2 the data used 
for the scene description and in section 3 the modeling 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996