3D RECONSTRUCTION AND RENDERING FOR A VIRTUAL VISIT
A. Georgopoulos‘“, C. Ioannidis‘
‚ A. Daskalopoulos“, E. Demiridi
(? Professor, Laboratory of Photogrammetry, drag(@@central.ntua.gr
(9 Assistant Professor, Laboratory of Photogrammetry, cioannid@survey.ntua.gr
(2 Surveyor Engineer
School of Rural & Surveying Engineering
National Technical University of Athens
Commission V, WG V/6
KEY WORDS: Cultural heritage, 3D rendering video, Digital Orthophotography, Modelling, Animation, Orthoimage
ABSTRACT:
In this paper the steps for the production of a complete 3D digital rendering and 3D virtual tour in the exterior and the interior of the
church of the Dafni Monastery is presented and described in detail. During a strong earthquake three years ago, the Byzantine
Monastery of Dafni in Athens suffered severe damages. This particular monument is considered one of the most important specimens
of Byzantine art and architecture worldwide and has been included in the World Heritage by UNESCO.
For this effort it was necessary to create a wireframe model, a surface model and, finally, a textured model on which the final
rendering and animation were based. Special considerations were made as to the use of such models and their accuracy requirements.
All textural material required for the rendering was extracted from photogrammetric products, like accurate orthophotomosaics and
rectifications, using digital image processing techniques, while keeping the high quality of the final digital model. Special decision
making on technical issues was required, for the final product to be easy to use, aesthetically correct and demanding the least possible
storage volume. Attention was given to the appropriate selection of the camera moving path for the creation of the video and the
resolution of the images. Also, special care was given to the internal side of the church where there are large, unique and very
detailed colourful mosaics, which are considered to be the masterpieces of the Byzantine art. In order to achieve an easier and cost
effective way for the whole process, two broadly used commercial software programms, AutoCAD® and 3DStudioMax®, were used.
The final virtual tour was constructed using suitable specialized commercial video editing software.
1. INTRODUCTION
3D modeling and visualization of monuments constitutes a very
sophisticated and integrated method for the geometric recording
for the documentation and for the preservation of cultural
heritage. It is particularly effective when applied for the
documentation of significantly large and complicated
monuments. When the 3D modeling is composed by high
accuracy detailed data, it is in fact the final product of a long
and expensive series of processes with a number of intermediate
products, such as 2D and 3D, vector and raster plans.
Photogrammetry in principle uses photographic images of the
objects of interest as raw data. Complicated techniques have
been developed over the years in order to produce specialized
visualisations — mostly orthogonal projections, vector or raster —
of these objects of interest from these particular images. Lately
sophisticated digital techniques have been developed in order to
produce three dimensional views of these objects on computer
screens, thus satisfying the necesssity of the human observer to
grasp the environment in 3D. In this way the trip, which started
at the real object returns to it via a series of image
transformations and representations (Figure 1).
Laser scanning instrumentation and related software is perhaps
the future tool for achieving such 3D visualisations. This
impressive and ambitious technology is evolving very fast.
However traditional techniques may still play an important role,
63:
as they are able to exploit the detailed work carried out by
traditional photogrammetric techniques, which are characterized
by indispensable accuracy and detail qualities. Therefore for
certain applications of 3D visualization of objects, classical
techniques should still be used with impressive results.
image Understanding
Image Processing
Computer Computer Vision
] OBJECT Digital Photogrammetry
Graphics SPACE ( (
<P Geometric Y
Relationships RU
Figure 1: The round trip from object to image
The Dafni Monastery is one of the two remaining today
excellent specimens of the culmination of Byzantine
architecture (Figure 2). It was built in the 11" century and is
situated in the southeastern part of Attica near Athens. The
whole monastery extends on an area of 0.7 hectars and in the
centre of that area lies the majestic central church, the
Katholikon. In essence it is a cross-domed octagon type of
church extending approximately 25x15 m? and 20 m in height.
2
TI
