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Journal of Cultural Heritage 10S (2009) e112–e117

Original article

Ancient contexts and virtual reality: From reconstructive study to theconstruction of knowledge models

Francesco Gabellone ∗National Research Council (CNR), Institute for Archaeological and Monumental Heritage (CNR-IBAM), Via Monteroni campus Universitario, Lecce, Italy

Received 27 July 2009; accepted 6 October 2009Available online 17 November 2009

bstract

This paper describes the use of integrated methods for the creation of three-dimensional models using laser scanning techniques, digitalhotogrammetry, 3D photomodelling and direct surveying. The three-dimensional models established using these methods constitute the basis forhe construction of advanced information platform, able to represent the buildings under study with great accuracy at various scales, including bothetailed elements and the monumental arrangement as a whole, as well as the textural features of the internal and external surfaces. The main aimf our studies is to enable the public to enjoy the results of archaeological and historical researches, via the web or stand-alone products, and tovirtually visit” the monuments using RealTime 3D visiting systems. As well as showing the current state of the monuments, the visit includes

econstructions of previous phases in their history and examples of virtual restorations of the wall paintings. All the textures were obtained byrocesses of photomodelling and were applied to the geometrical forms in accordance with the radiosity algorithm, with lights and shadows of thearea’ type. The result of this integrated approach is extremely life-like, almost indistinguishable from reality.

2009 Elsevier Masson SAS. All rights reserved.

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eywords: Virtual heritage; Photomodelling; Realtime 3D; Photorealism; Virtu

. Research aims

The advent of virtual reality and especially computers markednew beginning [1]. Somehow they provided a different per-

pective on reality, allowing for an alternative “reading”. Theost significant results in the construction of knowledge plat-

orms in VR have been achieved in EU projects such asyHeriNet, Archeotour, Interadria, Interreg Greece–Italy, etc.hese projects were guided by the belief that in order to beffective, the process of communicating Cultural Heritage to theider public should be as free as possible from the sterile old VR

nterfaces of the 1990s. In operational terms, this translates intoolutions that are as lifelike as possible and guarantee the max-mum emotional involvement of the viewer, adopting the sameechniques as are used in modern cinema. Communication thus

ecomes entertainment and a vehicle for high-quality content,imed at the widest possible public and produced with the helpf interdisciplinary tools and methods. In this context, high-end

∗ Tel.: +390832422200; fax: +390832422225.E-mail address: f.gabellone@ibam.cnr.it.

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296-2074/$ – see front matter © 2009 Elsevier Masson SAS. All rights reserved.oi:10.1016/j.culher.2009.10.001

it; 3d modelling; Archaeology

echnologies are no longer the goal of research; rather they arehe invisible engine of an unstoppable process that is making itarder and harder to distinguish between computer images andeal objects [2]. This marks a shift away from the rigid focus onurely technical issues that prevailed in the past.

. Introduction and state of the art

The main effort of Computer Graphics during the last fewears is represented by the search of the photorealism [3]. Oldalculators achieved the delivery of the depth by combiningogether simple algorithms aimed to visualize solids under arospective slant, only thanks to lines that depicted their con-ours (the so-called wireframes). This primitive representation,as quite soon replaced by algorithms that allowed to eliminate

he hidden lines and then by shadowing systems able to simu-ate the illumination of the surfaces. Subsequently, the raytracingechnique was introduced. It allowed to simulate the transparen-

ies, the reflections and the shadows. Nowadays, the delivery ofhe synthetic images has reached a very refined level thanks to thentroduction of the radiosity, through which the computation ofhe illumination accounts for the multiple environmental inter-

ral Heritage 10S (2009) e112–e117 e113

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F. Gabellone / Journal of Cultu

ctions. In this fashion, it has opened the way to make eventuallyndistinguishable the synthetic and the real images. Within thenternational scientific community, the photorealism has beenositively welcomed in all the sectors of the entertainment. Hol-ywood movies and videogames strongly exploit the emotivempact and the astonishment effect that Computer Graphics canransmit thanks to the hyper-realistic visual effects. Moreover, inhe last few years this phenomenon has meaningfully involvedlso the scientific community. In particular, it is relevant to thetudy and the communication with computer vision systems, tohe simulation of physical phenomena and the archaeologicaleconstruction of ancient contexts.

. CNR-IBAM experience

For many years, the Italian National Research Council’somputer Laboratory (IbamITLab) in Lecce has followed an

ntegrated approach to the sharing of technological know-how.hile, on the one hand, there have been efforts to reach out

o private companies and specialists and involve them in pro-esses of technological exchange which will have a positivempact on development, on the other hand, the greatest con-ern of researchers is the so-called “general public”, the worldf the non-specialists. Our experience in this sector has shownhat technology is not the objective of research, but ratherhe instrument with which to channel information towards thisype of user. An emblematic case in this regard is the recon-tructive study of ancient contexts, where three-dimensionalraphics compensate for the limited expressive potential ofwo-dimensional drawings and allows for interpretative and rep-esentative solutions that were unimaginable a few years ago.he virtual space thus becomes an important opportunity for

eflection and study, as well as constituting a revolutionary wayo learn for the wider public [4].

. The virtualisation of archaeological items

Unlike movable finds, fixed archaeological items cannot, inost cases, be transported to a museum. By their nature, their

ate is often quite different to that of movable items, which areatalogued, cleaned, studied, and carefully looked after, whetherr not they end up on display in a showcase. Fixed archaeologicaltems are often stripped of the most precious objects that theysed to house, and even in the best-case scenario, i.e. when theyre not looted before being excavated, they are typically restoredn a hurry [5]. A similar fate often awaits those sites which, dueo specific problems of accessibility or the sheer impossibilityf creating an adequate system for visiting them, are closedo the public and are frequently unheard of by tourists. In thencient nuclei of many towns, these sites are like pieces of auzzle that has become illegible; they pose serious problems ofnowledge and documentation, in addition to problems relatedo monitoring their state of conservation, often compromised by

heir condition of semi-abandonment.

The numerous virtual itineraries constructed on the basis ofomputerised data by our laboratories constitute an attempt toescribe processes of cultural exchange and assimilation via a

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ig. 1. Screenshot of “Abriola Virtual Visit”, Realtime 3D platform for theistance visiting of Giovanni and Girolamo Todisco works. 3D model realizedith digital photogrammetry and manual modelling.

hree-dimensional representation in which the role of the ‘vir-ualised’ item is not to provide a perfectly life-like simulationf reality, or even worse a hyper-realistic alternative to reality,ut to be the starting point for the creation of an artificial worldhat enriches and decodes reality, obviously recreating it, butbove all interpreting it [6]. In accordance with this principle,his type of activity may fairly be described as the transforma-ion of an item into a distance museum piece, starting from theestitution in digital form of all the elements that are necessaryor the comprehension of given content. Digital models thusecome the informational basis for the development of navi-ation platforms, in the most advanced cases in RealTime 3D,hich make it possible to view and enjoy these items at a dis-

ance. The utility and effectiveness of this process, which weave called “museographical”, depends on how much informa-ion is transmitted to the final user, while seeking to “highlight”he value of the item with suitable communication tools and

ethods which are also appropriate to the users’ various levelsf interest and understanding (Fig. 1).

. Issues linked to virtual restoration

The acquisition of data starts with knowledge of the currenttate of the item and entails the formulation of reconstructiveypotheses which are used to channel information, not only con-erning what is directly observable in situ, but also and especiallyn those elements that are most difficult to read or decipher. Thisoint represents the precondition for an interesting applicationf Computer Graphics to the representation and interpretationf a work of art for educational purposes: virtual restoration,nderstood as the digital reconstruction of the original image ofhe item with the help of all available forms of documentation.here is currently much debate on the theme of digital (or virtual)

estoration, especially concerning the numerous methodologicalmplications that necessarily bind it to the discipline of ‘mod-

rn’ restoration, from which it was born. Modern restoration isounded on a basic principle: it must concern itself exclusivelyith the material aspects of the work of art, i.e. it must guaran-

ee respect for its value as a historical and aesthetic instance and

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ehasooodsurfaces and simple geometric shapes, while laser scanning waslimited to complex architectural elements (capitals, sculptures,etc.) (Figs. 3 and 4).

114 F. Gabellone / Journal of Cultu

ust limit itself to conservation of the materials of which theork itself is made. The term ‘virtual’, i.e. potential (and thuseither current nor material) suggests that it is no more than aorm of checking or verification ante rem of a hypothetical actf real restoration, and in no way could it be properly defined asrestoration’ itself. It is completely wrong, however, to think thathe digital world is not material; on the contrary, the numbers,mages, sounds and so forth that are produced on a computer areart of a new type of materiality, which has a physical consis-ency and its own domain of reference and circulation. Just likeeal objects, three-dimensional models have a measurable spa-iality, they express physical and chromatic values, they can beeplicated ad infinitum or be transformed into ‘tangible’ objectsy means of prototyping techniques; what is most important ishat they exist. Digital restoration can plausibly serve as a guiden acts of real restoration, helping to check many critical aspectsf the work; however, it can also take on a scientific value in itswn right if it enables us to visualise the work as it appearedn a certain moment of its life, restoring its value as historicalestimony to the civilisation that is exemplifies [7]. Of the manypplications of these theories by the Lecce-based IbamITLab inhe last few years, we cite here the study of the site of Santa

aria di Cerrate, which concerned both the outside of the com-lex and the interior of the church, with particular attention tohe virtual restoration of the frescoes visible today on the wallsf the smaller naves.

Past attempts at rebuilding involved the reassembly of thealls in a way that did not respect the original order of thelocks. As a result, the 14th-century fresco on the South wallf the church currently has the appearance of a puzzle. The dig-tal restoration has made it possible to rearrange the blocks inheir original position and subsequently to perform an icono-raphic reconstruction that enables the visitor to recognise theeal identity of the figures shown, while respecting the funda-ental demands and principles of modern restoration, above all

hat the intervention and its results be recognisable and distinctrom the original (Fig. 2).

. The experience gained in the ByHerinet project

The IbamITLab has made a comparative test of methods forhe creation of three-dimensional models using laser scanningechniques, photogrammetry and 3D photomodelling, appliedo Byzantine sites in the province of Lecce and the regionf Basilicata. The three-dimensional models developed usinghese methods provide a useful knowledge base for representingrchitectural morphology on various scales with great accuracy.his includes both specific details and the overall monumentalrrangement, as well as the textural characteristics of the interiornd exterior surfaces. Each monument was modelled and stud-ed in relation to its environmental context, noting its underlyingystem of relationships, which is often the key to understand-ng the architectural strategies adopted. The main goal of this

esearch, however, remains that of allowing the public to bene-t from the results obtained, either via the web or stand-aloneroducts, so that they may “visit” and enjoy the monumentssing RealTime 3D distance visiting systems, characterised by

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ig. 2. a: Santa Maria di Cerrate church (Squinzano, Lecce, South Italy), actualtate and digital restoration of Byzantine fresco; b: Santa Maria di Cerrate churchSquinzano, Lecce, South Italy), virtual restoration with completion of figures.

xcellent rendering and general performance. Our experienceas shown that the use of integrated techniques is far prefer-ble to the use of just one technique on its own, such as lasercanning. The numerous undercuts in the interior of the churchf S. M. di Cerrate would have required many weeks of work,bliging us to manage an enormous quantity of 3D data, muchf which would be superfluous. The use of photogrammetry andirect surveys neatly resolved the restitution of all the regular

ig. 3. Santa Maria di Cerrate church (Squinzano, Lecce, South Italy), screen-hot of Realtime 3D platform. The external view.

F. Gabellone / Journal of Cultural H

Fig. 4. Santa Maria di Cerrate church (Squinzano, Lecce, South Italy), screen-shot of Realtime 3D platform. The interiors.

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Fig. 5. a: Madonna delle Croci, Matera. The four phases of 3D restitution with laser scmapping patches; 3. UVW texture associated with the camera mapping method; 4. Th3D realistic view.

eritage 10S (2009) e112–e117 e115

The case of the rupestrian church of Madonna delle Croci,haracterised by extremely irregular surfaces, was quite differ-nt. The laser-assisted survey produced a mesh of three millionolygons, subsequently reduced to 300,000 polygons in ordero enable it to be used in real-time. In the texturing phase, theimited number of facets imposed by the performance of theealTime 3D engine considerably simplified the process of sub-ividing the overall model into patches. In the end, the modelas mapped using the Camera Mapping method, widely used

n cinematography, but rarely used in other applications such ashe restitution of monuments.

The hyper-realistic final result clearly derives from the skil-ul juxtaposition of the individual polygonal ‘sectors’ (patches)apped with these techniques, but the element that most con-

ributes to the photorealism is the illumination, which is as

lose as possible to the natural illumination seen in originalhotographs. The rendering of the illumination was based onRadiosity-type algorithm via the use of High Dynamic Range

mages (HDRI) [8] and area light coming from the church’s

anning technique: 1. The shading view of 3D model without texture; 2. camerae final 3D model with image-based lighting; b: Madonna delle Croci, Matera.

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Fig. 6. The Assyrian Room of Iraq Virtual Museum. 3D models obtained withimage-based technology.

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nly opening to the outside. Artificial light simply accentuatedhe atmosphere of closed, dark space. (Fig. 5 a–b).

. Image-based modelling for the construction of theraq Virtual Museum

In this project, all methodological decisions were basedxclusively on historical data. Every technical solution adoptedor the reconstruction of the Iraqi monuments and the individ-al rooms of the museum was guided by this one objective: toresent, concisely but thoroughly, the history of Mesopotamiaia video clips, records and images that may be understood byll users. As often happens when dealing with human creativ-ty, the process of simplifying the message and the content toe transmitted can become extremely difficult to manage. Theesult of these reflections is the identification of three funda-ental elements for learning: the first is the architecture of theuseum room itself [9]. The concept of a room in a museum is

ssociated with the broader notion of cultural and historic iden-ity: the setting up of virtual rooms has made it possible to gatherignificant pieces from the period of reference, enabling the vis-tor to immediately recognise the tangible signs of a particularay of life and thus to comprehend the features that establish

he distinctive character of the period. This approach recreatesn the virtual environment the familiar procedure of visiting aeal museum, helping the visitor to understand the value of thexhibit as testimony, which is the second and perhaps the mostmportant element in the creation of a museum. The exhibit linksorm and content indissolubly, and establishes a clear image ofhe historic period, facilitating the development of those cog-itive processes that are stimulated by visual memory, highlyffective in most visitors. In this sense, the use of technologyor three-dimensional representation of the exhibits becomes aeans of increasing their appeal even further, since a model that

an be explored interactively is undoubtedly more striking thansimple image. The 3D modelling of the exhibits was performed

o a large extent with rotoscoping techniques, using images thatad already been published or were available on the web; onlyn a few cases was it possible to use high quality images. Never-heless, many 3D exhibits on display in the virtual museum arelso valuable as documentation, because, thanks to image-basedestitution techniques, they make it possible to study details andake measurements. Emblematic in this regard is the reconstruc-ive study and photomodelling of the helmet of Meskalamdug,hich may be explored on the project’s website in RealTime 3D

10].The third element, extremely important from the museo-

raphical point of view, is the setting of the exhibits in theirontext of provenance. Very often in traditional museums,roups of exhibits of the same type are displayed in accor-ance with purely aesthetic criteria, neglecting their functionr symbolic significance in order to highlight individual stylis-ic aspects. However, there are sculptures such as the Assyrian

amassu or the orthostats of Khorsabad, which would beractically incomprehensible if removed from their specificrchitectural contexts [11]. This led to the idea of describinghe complexity of these situations by means of animated video

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ig. 7. The Acheamenid and Seleucid Room. 3D models obtained with image-ased technology.

lips, in which the exhibit is reconstructed together with its con-ext of provenance, regional surroundings and city environmentFigs. 6 and 7).

. Conclusions

The creation of a virtual navigation platform in real-timentails the use of three-dimensional models with a small num-er of polygons in order to guarantee optimal viewing witheasonable response times [12]. The speed of the system is indis-ensable for the emotional involvement of the user in a virtualontext. The results shown in these pages derive from a mea-ured equilibrium between level of modelling and realism of theextures, which helps to compensate for the deficit of microge-metric detail, necessarily inferior with respect to reality. Evenhough the high technological level and the greater power ofommunication implicit in the interactive RealTime 3D sys-ems already described, the public now seems more interestedn passive systems like the movie or animated virtual presen-ation, probably for the greater communication impact. In ourork, both solutions are anyway characterized by a high levelf realism.

The purpose of this type of works remains essentially com-unicative and museum-oriented; it represents an extremely

ffective way of surveying the current state of an item and ofnabling distance viewing of both accessible and inaccessible

ites, thanks to them the user can not only learn but also bencouraged to pay a visit in situ. This can only facilitate theon-virtual (but highly important) process of capitalisation ofultural Heritage.

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cknowledgments

Our thanks to Ivan Ferrari, Francesco Giuri and Massimoimoncelli, researchers at the IbamITLab, and Claudio Ger-inario (Lecce, Accademia di Belle Arti student), for their

mportant contributions and for the great sense of team spirithich they brought to our common endeavour.

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Symposium on Virtual Reality, Archaeology, and Cultural Heritage, Pisa,Italy, December 2005.

[4] M. Levoy, The digital Michelangelo project, Proceedings of the 2nd Int.Conference on 3-D Digital Imaging and Modeling, Ottawa, Canada, Octo-ber 1999 (pp. 2–13).

[5] M. Cultraro, F. Gabellone, G. Scardozzi, Integrated methodologies andtechnologies for the reconstructive study of Dur-Sharrukin (Iraq), in:

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[6] R. Scateni, P. Cignoni, C. Montani, R. Scopigno, Fondamenti di graficatridimensionale interattiva, Mc Graw Hill, Milano, 2005.

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[8] P. E. Debevec, C. J. Taylor, J. Malik, Modeling and Rendering Architec-ture from Photographs, in: Proceedings of SIGGRAPH Conference, LosAngeles, 1996.

[9] F. Gabellone, G. Scardozzi, Integrated technologies for the reconstructivestudy of Mesopotamian cultural heritage: the cases of Ur, Uruk and Nimrud,in: Proceedings of the International Congress “Cultural Heritage and NewTechnologies”, Workshop 11 - Archäologie und Computer, October 18–20,Vienna, 2006, on CD-ROM.

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11] M. Cultraro, F. Gabellone, G. Scardozzi, From remote sensing to 3Dmodelling and virtual reconstructions of the Iraqi archaeological sites:the case of Hatra, in: R. Lasaponara, N. Masini (Eds.), Proceedings ofthe 1st International Workshop on Remote sensing for Archaeology and

pp. 239–242.12] P. Cignoni, R. Scopigno, Sampled 3D models for CH applications: an

enabling medium or a technological exercise? ACM J. Comput. Cult. Herit.1 (2008) 1–23 (article no. 2).