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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004 
The Monastery is considered to be the Parthenon of the 
Byzantine era and is internationally protected by UNESCO. 
  
Figure 2: The Dafni Monastery 
The strong earthquake of 7^ September 1999 in the greater 
Athens area caused severe damage to the Katholikon and the 
rest of the buildings of the monastery. The Ministry of Culture 
immediately decided to take strong measures in order to protect 
the monument. Before any static or structural interventions a 
thorough survey of the monument at a general scale of 1:25 was 
decided. The Laboratory of Photogrammetry of NTUA 
undertook this task. 
A complete and thorough geometric recording of the monument 
has been carried out. In addition it was decided to produce a 3D 
digital model based on the aforementioned survey. The 3D 
rendering could make use of all conventional survey 
measurements and digital photogrammetric products. These 
products were either raster orthophotographs or vector 
drawings. 
The aim of this research project was to exploit the available data 
in order to produce a three dimensional rendered virtual tour of 
the monument. In this way the detail and realistic impression of 
the data from the geometric restitution would contribute to the 
virtual rendering. At the same time high amount of detail would 
be included in the final product, in order to give it a high degree 
of realistic impression. 
The virtual tour should be constructed using suitable specialized 
commercial software. However particular decisions ought to be 
made as far as camera settings and orbit, lighting and ambiance 
specifications were concerned. The resulting video lasts for 
something less than 6 minutes and gives a pretty good idea of 
the interior and the exterior of the monument. 
Similar efforts have been repeatedly reported in recent 
bibliography (Benning et al. 2001, Cantoni et al. 2001, Gruen et 
al. 2002, Kraus 2003, van der Lei 2003). It is evident that there 
is a growing interest in 3D representations of objects in the 
technical community. Considerations such as producing realistic 
video sequences or suitably projecting as much amount of detail 
as possible have been addressed by all researchers. Hence it was 
thought to be useful to attempt yet another effort trying to 
exploit a highly detailed geometric documentation available for 
the particular monument. 
  
2. THE GEOMETRIC RECORDING 
The project of geometrically documenting the Katholikon of the 
Dafni Monastery started late in December 1999 and lasted for 
about two years. The fieldwork covered approximately 3076 of 
this time and for the purposes of the project around 11500 
points were measured and 1000 photographs were taken. Digital 
photogrammetric techniques, mostly performed on a Z/I SSK 
workstation, were employed for the production of the final 
products. With the biggest part of the project already finished, it 
was decided to produce a 3D digital model. Apart from the raw 
data of the survey, the various vector and image products 
available for that purpose were: 
1. Vector drawings of six outside facades, i.e. including the two 
crossections of the outer knave, and of the five double 
longitudinal and five double crossections through the inside of 
the monument. In total 26 drawings at a scale of 1:25 and 1:50 
were available. 
2. Colour photomosaics, i.e. image orthogonal projections 
corresponding to the 26 drawings of (1) at a scale of 1:25. 
3. Vector drawings of horizontal sections at five different levels 
and a zenith view of the Katholikon at a scale of 1:25 and 1:50. 
4. The zenith view of the monument with image projections of 
the mosaics at a scale of 1:25. 
5. Orthogonal image projections of all mosaics at a scale of 1:5. 
6. Mathematical developments of the images of all mosaics 
situated on developable surfaces (i.e. cylinders, cones etc.) at a 
scale of 1:5. (Georgopoulos et al., 2001) 
7. Cartographic developments of the images of all mosaics 
situated on non developable surfaces (ie. second order 
surfaces), choosing such a projection in order not to distort the 
figures depicted on the mosaics and, of course, their asthetic 
value. (Valanis, 2002). 
8. A Data Base built on a GIS philosophy, for the interrelation 
of all available information for all parts of the monument 
(Georgopoulos et al., 2003). 
In addition, other general helpful data were also available and 
their use will be indicated later. They included a set of 35mm 
oblique pictures taken from a helicopter, showing the church 
from different angles and selected scanned vertical photos taken 
from the helicopter from a height of approximately 30 meters. 
3. CONTRUCTION OF THE VIRTUAL VISIT 
For the creation of the 3D virtual tour of the Church, three basic 
steps were necessary, mainly in order to model the 3D object 
within the electronic environment. These steps included: 
= the creation of a wireframe model, 
= a surface model and 
= a textured model with the final rendering and animation. 
They were planned and carried out using two commercially 
available software programs, ie. AutoCAD 2000” from 
AutoDesk and 3DStudio Max”. The initial pieces of 
information available were the  geodetically — and 
photogrammetrically determined points (Figure 3). 
3.1 Wireframe model 
A wireframe model consists of a series of points — vertices at 
characteristic points of the monument and the lines in space — 
and the edges connecting these vertices. Therefore the main task 
of this step was to define the position, with the help of three 
dimensional coordinates, of the vertices necessary for the