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3D Modelling and Visualization in Field Archaeology. From Survey To
Interpretation Of The Past Using Digital Technologies
Article  in  Groma Documenting archaeology · April 2020
DOI: 10.12977/groma26
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D. Ferdani, E. Demetrescu, M. Cavalieri, G. Pace, S. Lenzi
GROMA | documenting archaeology
ISSN: 1825-411X | Vol. 4-2019
DOI: 10.12977/groma26 | pp. 1-21
Published on: 09/04/2020 | Section: Article
License: CC BY-NC-ND 4.0 International
3D Modelling and Visualization in Field
Archaeology. From Survey To Interpretation
Of The Past Using Digital Technologies
Over the last few decades, there has been a growing interest in the fusion of the humanities and the hard
sciences. The continuous experimentation and contamination between these two disciplines has led to
the emergence of new horizons of research and open to perspectives and issues previously unthinkable.
Finally, it has started the development of specific technologies for the cultural domain. Among these
technologies, virtual archaeology, which we could define as the set of processes of acquisition, analysis
and interpretation aimed at visualizing and simulating the past using 3D digital technologies and a
theoretical and multidisciplinary scientific approach, has now reached its maturity. In this contribution
the potentials in using 3D modelling as a tool of investigation and visualization for a deeper understanding
of archaeological sites is presented. The discussion is supported by the case study of the roman villa
of Aiano, built at the beginning of the 4th century A.D. and characterized by monumental architecture
and decorations.
Introduction
This paper focuses on the use of digital 3D technologies in archaeology and the
potential of computer-based visualization as research tools to support the interpretation
and modelling of archaeological data.
Very often, in fact, graphic models of ancient artefacts and architectures are excluded
from the interpretative process and are only considered as mere communicative
visualization or public fiction rather than scientific tools1
. The application of 3D
modelling and visualization tools, if integrated in the cognitive and interpretative
process, following a systematic scientific approach, can lead to a deeper understanding
of the archaeological context2
. After a discussion on the current state of the art
computer-based visualization in archaeology, some theoretical aspects necessary
for the creation of a reliable project of virtual archaeology will be discussed.
1  Demetrescu 2018
2  Ask 2012, 9-10
D. Ferdani, E. Demetrescu, M. Cavalieri, G. Pace, S. Lenzi 2
In the second part of this article we will describe a proven workflow of 3D modelling
and visualization in archaeology applied to the case study of the Roman villa
of Aiano. It will be deepened how the 3D model of the archaeological excavation,
acquired with photogrammetric techniques, has been used in combination with
the reconstructive 3D model. It will also be described how the reconstructive process
has been traced through the registration of sources and paradata used to ensure
the transparency of the process of archaeological interpretation.
Dealing with the reconstruction of the past
The use of computer-based visualization to show hypothetical reconstruction of
the past within the Cultural Heritage domain dates back to the end of the 80s.
However, as Clarks points out, the idea of reconstructing the past has been part of
archaeology almost since its origins. In 1990, Paul Reilly, with his paper: “Towards
a virtual archaeology”, formalised for the first time the term “Virtual Archaeology”
to describe the use of computer-based simulations of archaeological excavations3
.
In the last two decades with the development of computer graphic technology,
computer-based visualization has made enormous progress in terms of graphics
rendering and realism. This development has also had a great impact on virtual
archaeology4
. The main consequence is that the Reilly’s concept5
of “simulation”
has been lost in sight and the term “reconstruction” has been widely used to refer
to these visualizations. Many archaeologists have criticized this term as it could be
misleading since the 3D model of the past are tools for better understanding the
past and not statements of reality6
. Given the idiom “seeing is believing”, the realism
achieved by modern visualization systems could lead the users to perceive the
virtual model as “truth” instead of a result of interpretation. For this reason, every
virtual reconstruction should have adequate mechanisms to declare the level of
authenticity allowing to distinguish what is real from what is interpreted. Clark7
complains that most virtual reconstruction are not provided with such mechanisms.
This is often due to the fact that making transparent all the sources that led to
the development of a hypothetical reconstruction is not easy, especially when dealing
with complex contexts or conflicting information. These criticisms were certainly
also generated by the fact that the first applications of virtual reality for 3D
visualization of archaeological data had several weaknesses. As Forte8
underlines,
in the first applications of virtual reality for 3D visualization of archaeological data
3  Reilly 1990, 133
4  See Barceló et al. 2000, Frisher et al. 2002, Sanders 2008
5  Reilly 1990, 133
6  Clark 2010, Forte 2010, Baker 2012
7  Baker 2012, 164
8  Forte 2000
GROMA 4 - 20193
there was a lack of consistent virtual archaeological projects aimed at finding precise
answers using digital technologies. In fact, many projects were more focused
on technological spectacularization and dissemination aspects rather than scientific
research. The first models were not “transparent”, in respect to the sources and the
reconstructions were presented as peremptory without offering alternative hypotheses.
Finally, there was a lack of interdisciplinary professionals who would have
linked the humanities with the computer world. Indeed, despite prudences and
criticisms, many benefits have been considered by the scientific community. Sanders
in “Why do virtual heritage” explain the specific benefits of using interactive
3D modeling in the field of cultural heritage saying that it is not merely visualization
but it “takes advantage of the digital medium to [...] produce new insight into the
past, which after all is what archaeology is supposed to be all about”9
. According to him,
among others, virtual heritage is the better way to test complex hypotheses, to
visualise intrasite change and development and to visually absorb complex dataset
about the past. Hermon and Nikodem also emphasize the use of 3D modeling as a
research tool and underlines the cognitive value of 3D visualization as it facilitates
the understanding of complex information10
. Over the years, methods, theory and
principles have been developed to regulate the use of computer-based visualization
by scientific community.
The Intellectual transparency
As described above, a project of virtual archaeology requires a scientific approach
to get a consistent and thorough visualization model of the past and in order to
avoid the ambiguity of the “black box effect”11
(reconstructive models seem to be
fictional despite they have been made following a scientific approach). As a result of
the scientific debate on virtual reconstruction, numerous projects and documents
aimed at creating efficient guidelines and good practices in the field of scientific
visualization of the past have been implemented over the years such as the London
Charter12
and Seville Principles13
. Scientific project and consortiums also have
contributed to the research providing tool and support, as in the case of 3DVisa14
,
V-Must15
and also Ariadne infrastructure16
and 3D-coform17
(even if the latter are
9  Sanders 2008, 564
10  Hermon and Nikodem 2007
11  Demetrescu 2018, 105
12  http://www.londoncharter.org/preamble.html
13  http://sevilleprinciples.com/
14  http://3dvisa.cch.kcl.ac.uk/index.html
15  http://www.v-must.net/
16  https://ariadne-infrastructure.eu/
17  http://www.3d-coform.eu/
D. Ferdani, E. Demetrescu, M. Cavalieri, G. Pace, S. Lenzi 4
more oriented towards digitization and visualization services). These initiatives
arise from the awareness of the potential of computer-based visualization of heritage
but also from the need for a theoretical debate and principles with practical
implications to regulate its use and minimize its weaknesses and inconsistencies.
The London Charter is one of the most internationally-recognized documents
which defines a set of principle of computer-based visualization to ensure the intellectual
and technical integrity, reliability, documentation, sustainability and ac-
cessibility18
. In particular it points out the importance of structuring and documenting
not only the sources used and their metadata but also the interpretation made
to achieve the visual representation. This aspect is particularly important when
dealing with virtual reconstruction19
.
In the next sections after a brief description of the case study, the workflow adopted
to achieve 3D hypothetical reconstruction of archaeological records and the
scientific approach used to deal with sources and paradata management and uncertainty
problems, will be illustrated.
The case study
Since 2005, an Italian-Belgian mission coordinated by the UCLouvain as part of
the international project “VII Regio. The Elsa Valley during Roman Age and Late
Antiquity”, has carried out numerous excavation campaigns in the area of Aiano,
near San Gimignano, in a site of great interest for the significant findings of the
18  Beacham, Denard and Niccolucci 2012, Denard 2012, Denard 2013, Hermon, Sorin and
Niccolucci 2018
19  Ferdani et al. 2014
Fig. 1. A) aerial view
of the archaeological
site. At the top right
the foundations
of the trefoil hall
and ambulatio are
still visible. The red
arrow highlights
the position of the
detail B within the
site; B) detail of the
preserved floor of the
trefoil hall.
GROMA 4 - 20195
Roman era (IV - VII century A.D.). During the archaeological excavations, researchers
identified a villa probably built between the end of the 3rd and the beginning
of the 4th century A.D. with monumental architecture and decorations (fig. 1).
The 2005 – 2019 campaigns led to the discovery of a villa of 10.000 square me-
tres20
. Only one third of the surface has been excavated at this moment. The oldest
building, dates back between the late 3rd and the early 4th cent. AD and is located
in the S-W area of the settlement: only the foundation walls are left. Between the
late 4th and the late 5th cent. AD, the entire settlement underwent a monumental
rearrangement, which turned it into a veritable architectural unicum21
.
The chief feature was a six-foil hall surrounded by a corresponding ambulatio.
According to archaeological records, at the beginning of the fifth century, three
foils were destroyed, and three little rectangular rooms replaced them. The central
room became a trefoil hall, with a floor decorated with mosaic details in geometrical
and figurative patterns – the only surviving floor of the entire villa22
. This room
was surrounded by a polylobed ambulatio, thus becoming an architectural unicum.
Between the late 5th and the mid-6th cent. AD the villa was abandoned, and new
workshops were set up; the furnishings and building materials were taken away to
be melted, recycled and reused23
.
When found, the decorations of the villa (marble, glass sectilia, mosaics, frescoes
and stuccoes) had been deprived of their original purposes, since they had been
disassembled or recycled during the last stage in the life of the site24
. The site was
completely abandoned during the seventh century AD.
Methods into practice
The process of creating hypothetical models of the past (objects, buildings or sites)
is the most challenging and complex task to be performed by researchers. It is
strictly connected to a meticulous work of philological interpretation based both
on a combination of data derived from several heterogeneous sources and on the
involvement of different professionals (archaeologists, expert in different subjects,
heritage architects, historians etc.). The quality and completeness of the modelling
is influenced both by the quality of the data collected and by the way in which
these data are cross-referenced and analyzed to propose reconstructive hypotheses.
20  Cavalieri and Pace 2011.
21  See in particular: Cavalieri, Pace and Lenzi 2019
22  Cavalieri 2010: the floor is a “cementizio”
23  Cavalieri, Lenzi and Cantisani 2013, Deltenre and Orlandi 2016
24  Cavalieri 2009, Cavalieri 2011, Cavalieri et al. 2012, Cavalieri 2013, Cavalieri, Lenzi and
Cantisani 2013, Cavalieri, Camin and Paolucci 2016, Deltenre and Orlandi 2016, Cavalieri,
Paolucci and Camin 2018, Cavalieri, Pace and Lenzi 2019.
D. Ferdani, E. Demetrescu, M. Cavalieri, G. Pace, S. Lenzi 6
Often the data collected in the field are not sufficient to define a complete hypothesis
and therefore it is necessary to rely on additional material such as historical
and iconographic documents - containing information on the manufacts - testimonies
and comparisons (e.g. similar technological solution found on architectures
built in the same period).
Research problems and expectations
The archaeological site of Aiano presents many critical issues due to the state of
conservation of the artifacts and the amount of available documentation collected
in 15 years of researches. As specified in the previous section, in fact, only the
base of the walls is preserved and many decorative elements (such as mosaic tesserae,
marbles, stuccoes, fragments of wall paintings) have been systematically found
outside their original context as they were dismantled and recycled during the last
period of the site’s life. It follows that it is no longer possible to determine their
precise original location making the interpretation of the decorative apparatus
even more complex.
Furthermore, as already said, the central room has a peculiar configuration which
turned it into an architectural unicum. Stylistic comparisons and functional analogies
are therefore difficult to establish except for technical and architectural aspects.
In the project of the Villa Romana in Aiano, we believe that the use of virtual archaeology
as a research tool could offer a valuable contribution to the understanding
of the site especially for the late antiquity, preserved only in a residual way.
Our expectation was to exploit the 3D simulation to test and visualize reconstructive
hypothesis. It could have helped us to compare the digitized archaeological
evidences and interpretations developed the investigations. Furthermore, connecting
and organizing in a structured way all the data coming from the archaeological
investigations on the 3D model could have helped to improve the analysis
of the monument allowing to refine interpretation, test hypotheses, find new so-
lutions25
. The present research, limited for now to the area of the so-called “trefoil
hall”, has involved challenging and complex steps in which we dealt with aspects
and problems concerning the integration of gaps, the degree of reliability of the
hypothetical reconstruction proposed and the management of “transparency” in
the representation of the archaeological data.
Digitisation of the archaeological site
The first step performed was the geometric acquisition of the archaeological sites
in its current state of preservation based on 3D surveying measurements with the
25  Ferdani and Bianchi 2016.
GROMA 4 - 20197
aim to create a Digital Replica26
of the site. The analysis of the architectural complex
is a fundamental documentation to operate correctly in the interpretation of the
evolutionary phases of the buildings. Nowadays several image-based and rangebased
scanning techniques are commonly used in digitization of cultural heritage27
.
In this context we used Dense Image Matching (DIM) techniques. DIM exploit
photogrammetry and computer vision algorithms to obtain 3D models of an object
along with true color information from a series of photos of an object taken using
defined procedures and using specific softwares for image processing and 3D spatial
data generation. The survey has been extended to the entire complex, focusing
on the units that concern the trefoil hall. The field work was divided into 2 steps:
topographic and photogrammetric survey. Since images themselves do not provide
metric information, in order to derive metric 3D results from the photogrammetric
procedure, a topographic network of Ground Control Points (GCP) was required.
A detailed inspection was carried out in order to plan a survey scheme and locate
several checkerboard registration targets as GCP for the construction of a topographic
network. Then we started. Firstly, 5 main GCP were placed along the
boundaries of the excavation area as topographic bases and then measured with a
double differential GPS to be able to geolocate the survey. Subsequently, 20 targets
were positioned and measured with a total laser station Topcon GPT7503 positioned
and oriented on a GPS basis in order to record data in absolute coordinates. The
targets were distributed evenly throughout the surface of the excavation.
Given the dimension of the site we mounted the photographic sensor on a Unmanned
Aerial Vehicle (UAV) controlled manually by a pilot using a remote control
and a ground station connected with the camera mounted on the UAV, while
26  Demetrescu et al. 2020.
27  Remondino and Rizzi 2010, Remondino and Campana 2014.
Fig. 2. A) registration
of topographic GCP
with a differential
GPS; B) ground
control station with
2 remote controllers
(for UAV and Gimbal)
and 2 monitors connected
in streaming
with 2 video cameras.
The first camera is
mounted on the chassis
to drive the UAV,
and the second one is
located on the gimbal
to control camera
movements.
D. Ferdani, E. Demetrescu, M. Cavalieri, G. Pace, S. Lenzi 8
a camera operator controlled a gimbal system28
with a second remote controller in
order to orient the camera towards the area to be surveyed (fig. 2).
The camera used is a Canon Eos 6D with a full frame CMOS sensor with a
12.1-megapixel matrix, equipped with a 35mm lens, which ensured high quality
images to be captured. The camera was programmed to take 1 photo every 2 seconds
to cover the entire area and assure sufficient overlaps among photos. The
UAV used is an octocopter DJI S1000. It was piloted at approximately 5 m from
the ground level to get the resolution of the photos close to 1 cm/pix for the trefoil
hall and 10 m for the whole site. 3 Flights and 30 minutes of acquisition were necessary
to survey the entire site.
The acquisitions were performed in the evening when the site was completely in
the shade of the hills behind it, taking advantage of diffuse light and absence of cast
shadows. After some tests we adopted an exposure time of between 1/800 with f/8
of diaphragm aperture and 800 ISO of light sensitivity to obtain aerial images of
the site in question. Subsequently, with the same camera, a terrestrial completion
measure was carried out for a better coverage of the walls of the roman villa.
The images were processed with Agisoft Photoscan, a photogrammetry software
for 3D spatial data generation. After importing images, the associated camera parameters
were computed by algorithm of “Structure From Motion” (SFM). Subsequently
the software through image matching procedures extracted and matched
biunivocal correspondence features among images in order to reconstruct camera
28  The gimbal is pivoted support which permits to move the camera along 3 axes and take stable
photos from different angles (from 90 to 45 degrees).
Fig. 3. Data processing
in Photoscan of
one of the flights. Camera
(blue rectangles)
position/orientation
reconstruction and
features extraction
(sparse colored
cloud) through SFM
algorithms. The result
of the photogrammetric
process allows to
see the path of the
cameras, performed
during the acquisition,
reconstructed in the
virtual environment.
GROMA 4 - 20199
position and orientation in space. After these steps the features extracted were associated
to 3D points resulting in a sparse point cloud (fig. 3).
Then the dense point cloud was computed by algorithms of “Dense Stereo
Matching” (DSM) employing all the pixels of the images. Finally, the points are
triangulated to obtain a mesh models with texture containing color information
derived from images (fig. 4).
The topology of mesh was optimized using remeshing filters in CloudCompare
software. This way it was possible to simplify the model by reducing the number
of polygons but, at the same time, to preserve texture and geometric quality
Fig. 4. Data processing in Photoscan. Dense point cloud computation through DSM algorithms; Solid mesh model obtained by point triangulation; Textured
model by projection of images.
Fig. 5. Outputs of the photogrammetric and optimization processes. A) digital model of the trefoil hall, in its current state of preservation, visualized in a
computer graphic software (Blender); B) high-resolution orthoimage of the hall.
D. Ferdani, E. Demetrescu, M. Cavalieri, G. Pace, S. Lenzi 10
in those parts with complex geometry and architectural details (such as mosaics).
The topographic network of points previously gathered with the total station was
appended to the model in order to scale and geo-reference the digital replica of
the site and control faults and distortions. Finally, the 3D model obtained was also
used to obtain high-resolution orthoimages of the site (plans and sections) from
different orthometric point of views (fig. 5).
Source collection and management
Historical and archaeological sources useful for supporting the philological interpretation
and designing reconstructive hypotheses were collected. According to
the 3rd principle of the London Charter “In order to ensure the intellectual integrity of
computer-based visualization methods and outcomes, relevant research sources should be
identified and evaluated in a structured and documented way”29
. Indeed, the reliability
of the interpretation, is influenced by the meticulousness of the work of collecting
and managing these data30
. For this purpose, a team of experts, which over the
years has followed the activities of excavation and research of the villa, has been
teamed up in order to structure and select all the available documentation relating
to the trefoil hall. The data used were as follows:
•	 metric survey of the extant structures over the years (2D-3D snapshots made
in a given moment in time).
•	 photos and sheets of collapsed structures (Special Finds - SF) whose original
position is inferable. E.g.: collapsed brick arches belonging to the vaults of the
apse rooms (fig. 6, A); collapsed false ceilings - made by wooden arches, reeds,
and plaster - (fig. 6, B).
•	 photos and sheets of fragments (SF) found not in situ as roof tiles and travertine
stones for the walls (fig. 6, C).
29  http://www.londoncharter.org/principles/research-sources.html
30  Gabellone 2018
Fig. 6. A) a collapsed
brick arch found in
the north-east apse
of the trefoil hall; B)
traces of the collapsed
plasters that covered
the ceiling; C) roman
tiles found during the
excavation.
GROMA 4 - 201911
•	 photos and sheets of archaeological finds (SF) found not in situ and moved
from their original context (spolia) such as marble, glass sectilia, mosaics, frescoes
and stuccoes (these archaeological materials were found in the site, but their
original position and complete decorative schema is unknown)
•	 archaeological reports and drawings (sources).
•	 theoretical building rules, theory of proportion and roman modules (“assumption”
sources)31
. Existing structures show measures attributable to multiples
of the Roman foot (fig. 6 A and C)
•	 comparison with other still-preserved buildings with similar structural or
functional solutions (sources).
The use of comparisons always requires a lot of caution because there is the risk of
creating prototypes or models that could have never existed. In this case, the architectural
uniqueness, has not allowed to identify relevant comparisons belonging
the same period and therefore it was necessary to expand the chronological range.
Given that, structural comparisons were made with late antique buildings from
the fifth century of the Ravenna territory, such as the Mausoleum of Galla Placidia,
the baptistery of the Arians and the Basilica of San Vitale. Functional comparisons
have been made with some poly-lobed rooms of the villa of Cazzanello in Tarquinia
and Casale in Piazza Armerina.
Interpretation and 3D mo-
delling
All the data collected
were cross-referenced and
analysed together with the
scientific committee in order
to conjecture a reconstructive
hypothesis that
was then simulated through
3D modelling techniques.
3D modelling was integrated
in the interpretation
processes and supported
them through simulations.
A first draft simulation of
the hall was designed with
computer graphic software
31  Pollio 2013
Fig. 7. Reconstructive
volumes of the hall
realized through
polygonal modelling
directly on the digital
replica of its actual
state of conservation
and chart of the reconstruction
process.
D. Ferdani, E. Demetrescu, M. Cavalieri, G. Pace, S. Lenzi 12
giving the archaeological remains architectural completeness. The reconstruction
was modelled on top of the digital replica and inherits its correct measures and
proportions allowing great accuracy and control during the process thus avoiding
the most common problems encountered when using two-dimensional drawings.
Overlapping digital replica of the site and its reconstruction made possible realtime
comparisons of dimension, orientation, height and stratigraphic units making
the connection between archaeological data and 3D model understandable and
helping the archaeologists to validate the proposed hypotheses.
Each version of the virtual model of the hall was evaluated until the scientific
committee approved a final version, philologically more reliable, discarding those
that are fallacious or less probable. Give that, the reconstruction can be considered
cyclical process since is repeated every time the model is modified (fig. 7).
Being the sources insufficient to reconstruct the entire building, simulations were
crucial to test and visualize speculations. The most challenging parts to be digitally
rebuilt were the roofing system and the elevated wall of the trefoil hall.
Given that, not only the visible structure but also the hidden architectural elements,
such as attics, wooden frames of the false vaults and ceilings, were modelled
in order to carry out a plausible simulation of the elevations. Firstly, the tiles and
embrices were modelled based on the measurements of the intact structures. Subsequently,
they were distributed over the entire surface of the roof in order to assume,
with a good approximation, the number of elements and their total weight.
Therefore, it was possible to suppose the type of wooden infrastructure for supporting
the roofs. The hypothesis of the existence of vaults in masonry was rejected
both because no archaeological remains were found and because of the excessive
load on the wall structures. In order to estimate the effects of loads on structures,
we didn’t use any structural analysis based on mathematical simulation as Finite
Element Method (FEM). Certainly, such analyses could have contributed to evaluate
our hypothesis, however it must be noted that FEM results are not always decisive
but they strongly depend on the exactness of mechanical parameters, which
often are difficult to evaluate especially in the cases of historical building32
. In this
case we based on data collected (absence of evidences), comparisons and empirical
data (wall thickness). In addition, the discovery of fragments of plaster made by
wooden reeds and mortar have led to the hypothesis of the presence of suspended
ceilings (USV 206 -220) and false vaults (USV211).
Regarding the central area of the hall, a structural comparison was made with the
Ravenna structures previously mentioned. Basing on these comparisons, it was assumed
that the central area had to be higher than the surrounding three apses and
rectangular rooms. In fact, considering the shape of the building, it was assumed
32  Frunzio et al. 2001, p. 598.
GROMA 4 - 201913
that the central room would necessarily be illuminated by a light source coming
from above. Furthermore, the apses were originally surmounted by brick arches
which enclosed the central space within a hexagon (fig. 8, A). Given that, the
hexagonal prism was considered the most logical and functional geometric solid
form to complete the upper part of the hall.
Other than comparison and structural issues, the height of the walls was assumed
considering also the multiples of the Roman foot33
and according to the architectural
proportional systems found in the plan of the building (fig. 8, A).
The design scheme identified in the plan, is characterized by a strong formal rigor,
symmetry and harmony in proportions. These aspects depend on mathematical
relationship between the architectural parts. The measurements found are multiple
of the Roman foot. The original design of the plan with six apses is obtained from
an intersection of major (lobes of the ambulatio) and minor circles (diameter of the
apses) which have geometric ratios of 1:1 and 1:2.
Given that it seemed that the plan of the building was based on a module (a part
providing the reference unit for the whole architecture)34
: the diameter of an apsis
(external 20 feet; internal 16 feet). We adopted this module to estimate walls elevation
(fig. 8, B). Obviously other proportional solutions were possible but this one
was chosen for two reasons. The first is the symmetry. The building has a width-
33  According to latin authors the “Roman foot” is 29,6 cm (Giuliani 1990, p. 283). However,
since the end of the 3rd century is attested the “Byzantine foot” which measures 31,48 cm (Salvatori
2006, 6). In our case the average measure is around 29,6 cm.
34  Gangwar 2017.
Fig. 8. A) measures in
meter and roman feet
(approximated) and
proportions of the
geometrical features
found in the layout of
the trefoil hall; B) reconstructive
section
A-B of the hall with
roman modules and
proportions applied
to the wall elevations;
C) section A-B of the
digital replica of the
hall.
D. Ferdani, E. Demetrescu, M. Cavalieri, G. Pace, S. Lenzi 14
to-height ratio of 1:1 - 1,6:1 considering the ambulatio - and the ratio between the
height of the central room and the apses of 1:2. The ratio between the diameter
of the apses and the diameter of the lobes of the ambulatio is also 1:2. Similar ratios
and symmetric proportions can also be observed in other late antique buildings
(although belonging to other contexts and with different functions). The second is
that higher walls could have overloaded the structure considering their thickness.
However, this interpretation might be updated with new hypotheses following
future discoveries.
As pointed out in the previous paragraph, archaeologists very often criticize the
value of virtual reconstructions aimed at public dissemination because they risk
conveying the wrong message, namely that the reconstruction is the truth instead
of a possible interpretation of the past. Moreover, such reconstructions are “black
box” and the source and interpretative reasoning is not declared. In order to overcome
such issue during the reconstruction we registered all the procedure using
the Extended Matrix approach35
.
Extended Matrix (EM) is a visual node-based formal language based on a stratigraphic
approach in use in archaeology. The term “extended” indicates that it
includes and defines not only archaeological stratifications (the superimposition of
single units of stratigraphy) but also their hypothetical reconstructions (the Virtual
Stratigraphic Unit - USV). Given that using EM it was possible to account, in
graph database, the sources used and the interpretation processes (paradata) that
35  Demetrescu 2015, Demetrescu 2018, Demetrescu et al. 2016
Fig. 9. Extended
Matrix of the trefoil
hall and an applied
example of virtual
stratigraphy with
related metadata and
paradata.
GROMA 4 - 201915
have led from archaeological evidences to the reconstructive hypothesis. Finally,
through computer graphic tools in the software Blender it was possible to connect
sources and paradata with the virtual reconstruction creating semantic transparent
models (fig. 9).
In the semantic model of the polylobed hall all the architectural or stratigraphic
elements were associated with a node entity that describes their properties (description,
physical properties, temporal relations, etc.) in the graph database. This
3D model is called “proxy”, namely a simplified prototype which allows to visualize
and interrogate the extended matrices containing excavation information and
the sources used in the reconstructive process (comparisons, assumptions, Roman
architectural rules) in order to help researchers in refining the final reconstructive
hypothesis.
Furthermore, the Proxy model allows a conceptual visualization using different
colour coding. In our case two colour codification was created. The former highlights,
in the digital replica, the different building phases (fig. 10, A). The latter
shows, in the reconstructive model, the different level of certainty basing on archaeological
evidences. The colours distinguish extant structures (red) and repositioned
fragments (yellow) from their completion and hypothetical reconstruction
(blue). The green colour finally paints all those parts for which we have no structural
or archaeological evidences, but their reconstruction is entrusted to comparisons
or interpreted sources (fig. 10, B).
Fig. 10. A)
proxy model
highlighting
building phases;
B) proxy models
highlighting level
of certainty.
D. Ferdani, E. Demetrescu, M. Cavalieri, G. Pace, S. Lenzi 16
After completing the interpretative process and approving the final reconstructive
hypothesis, the final representation model for a realistic visualization was created.
Through the use of polygonal modelling, details were added and the materials that
make up the structure (plaster, wood, terracotta, travertine) were characterized.
Into practice the physical behavior of materials was simulated in computer graphic
through the use of textures - which represent the base chromatic information and
were created from photographs - associated with shaders that control characteristics
such as reflection, refraction, roughness etc. It is a “figurative” model, and
although the complexity is optimized to respond to operational needs, it satisfies
characteristics such as the recognition of the geometry and the characterization of
surfaces with realistic chromatic information (fig.11).
Fig. 11. Trefoil Hall:
graphic representation
of the hypothetical
reconstructive
model (period 2,
phase 2 - end of 4th
- beginning of the 5th
century).
GROMA 4 - 201917
Conclusion
The article shows how the use of 3D modelling and visualization applied to archaeological
contexts can improve the interpretation of artefacts through simulations
and cognitive aspects.
In the presented case study is clear that, even before its publication, 3D models have
played an important role in supporting research, allowing discussion and comparison
of interpretative hypotheses and their verification through simulations and
visualization. From a communicative point of view, the use of the EM tool for a
“transparent” presentation and management of archaeological data and paradata,
improved cognitive processes by transforming the raw data into visual information.
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