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DIGITAL 3D RECONSTRUCTION OF SCROVEGNI CHAPEL
WITH MULTIPLE TECHNIQUES
A. Vettore *, A. Guarnieri *, M. Pontin®, J. A. Beraldin ^
| * CIRGEO - Interdept. Research Center of Geomatics, University of Padova, Italy - cirgeo@unipd.it
* Visual Information Technology Group, National Research Council Ottawa, Canada — angilo.beraldin@nre-enre.gc.ca
Commission V, WG V/2
Keywords: Cultural Heritage, Laser scanning, 3D Modeling
ABSTRACT
The use of 3D digitization and modeling in documenting heritage sites has increased significantly over the past few years. This is
mainly due to advances in laser scanning techniques, 3D modeling software, image-based-modeling techniques, computer power, and
virtual reality. There are many approaches currently available. The most common remains based on surveying and CAD tools and/or
traditional photogrammetry with control points and a human operator. This is very time consuming and can be tedious and lingering
effort. Lately, modeling methods based on laser scanners data and more automated image-based techniques are becoming available.
Initially, the goal of this work was to discuss advantages and disadvantages of those 3D modeling techniques applied to a cultural
heritage building, i.e. the Scrovegni chapel in Padova, Italy, by comparing the geometry and visual quality of related models for as-
built documentation, restoration and interactive visualization purposes. To this aim the chapel was imaged with a color digital camera
and surveyed with both different kind of laser scanners and traditional topographic instrument. Unfortunately due to the long time
wasted before all requested laser scanners were available from the dealers and difficulties encountered during the subsequent 3D
modeling, due to the bad quality of some range data, at the present date only the range data model is available.
Therefore in this paper we will discuss only the results obtained by generating a unique 3D model of the Scrovegni Chapel using four
different laser scanners: Cyrax 2500, Mensi GS 100, Optech ILRIS 3D and Riegl LMS-Z210. In order to assess the performance of
these sensors when applied for cultural heritage survey, data quality, geometric accuracy, sensor noise, ease of use, speed of data
collection, will be the topics of this work.
1. INTRODUCTION
Beside image-based modeling and traditional photogrammetric
survey, the use of ground-based laser scanners for 3D modeling
applications in the field of cultural heritage has become
recently very actractive, given the capability of laser sensors to
produce high-density point clouds of features in relatively short
time and without the extensive use of signalized targets. From
these point clouds, 3D models can be generated with sufficient
accuracy for as-built documentation, restoration plans, virtual
environment generations, interactive manipulation.
In order to compare the laser scanning technique with existing
3D surveying technologies such as image-based modeling and
photogrammetry, a joint project between CIRGEO (Interdept.
Research Center of Geomatics of the University of Padua,
Italy) and the VIT (Visual Information Technology, NRC,
Ottawa, Canada) was established, with the aim to create 3D
models of the inside of the Scrovegni Chapel in Padua, by
applying different surveying techniques. This church represents
à very actractive element of the national cultural heritage for
3D modeling applications. The Scrovegni Chapel presents a
simple architecture, being composed of a rectangular hall with
a barrel vault, an elegant gothic triple lancet window on the
facade, tall narrow windows on the southern wall, and a
polygonal apse. The interior can be therefore surveyed very
easily as no columns prevent a clear view of the walls and the
ceiling.
Furthermore, from artistic point of view, the Scrovegni Chapel
is considered a masterpiece in the history of painting in Italy
and Europe in the 14th century, as the vaulted roof and walls
are completely painted with frescoes, framing episodes in the
lives of the Virgin Mary and Christ, executed by Giotto in his
mature age. Along with 3D data, it was planned to collect
digital images of these frescoes, as well, in order to perform the
texturing of the final 3D model.
Regarding the laser scanner-based 3D modeling, we planned to
employ different kind of sensors in order to test and assess
their performance when applied for architectural surveying.
As we didn't.own any laser scanner at that time, all these
sensors were rented from corresponding Italian dealers.
Unfortunately, given the limited time of use allowed to us, the
church could not be completely surveyed using only one
sensor, therefore we were constrained to generate only one
model with the best range data set from all collected scans.
Moreover, given the long time wasted in this first part of the
work, at the present only the range-data modeling step has been
accomplished. Therefore in subsequent sections a description
of adopted processing methods and issues, we dealt with during
the generation of the 3D model of the Chapel, will be provided.
2. THE SCROVEGNI CHAPEL
For the Scrovegni Chapel, Giotto was asked to depict a series
of stories from the Old and New Testaments, culminating in
Christ's crucifixion and resurrection, and the Last Judgement.
The aim was to encourage visitors to the Chapel to meditate
more deeply on Christ's sacrifice and the salvation of mankind.
Giotto planned an architectural structure in painted imitation
marble supporting the vaulted roof, decorated as a star-
spangled sky, with framed stories of episodes in the lives of the
Virgin Mary and Christ on the walls (Figure 1). On the wall at
the end of the church, opposite the altar, is the grandiose
Universal Judgement, which concludes the story of human
salvation (Figure 2). The frescoes, painted between 1303 and
1305, follow three main themes :
