Virtual restoration. Paintings and mosaics

STUDIA ARCHAEOLOGICA 218 S T U D I A A R C H A E O L O G I C A 218 1 2 3 4 5 6 7 8 9 10 11 - De Marinis, S. Baroni, F. Laurenzi, L. Giuliano, A. Nocentini, S. Giuliano, A. Ferrari, G. Breglia, L. Lattanzi, E. Saletti, C. Blank, H. 12 13 14 - Canciani, F. - Conti, G. - Sprenger, M. 15 16 17 18 19 20 - Polaschek, K. Fabbricotti, E. Polaschek, K. Pensa, M. Costa, P. M. Perrone, M. 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 - Mansuelli, G. A. (a cura di) Fayer, C. Olbrich, G. Papadopoulos, J. Vecchi, M. Manacorda, D. Mansuelli, G. A. (a cura di) Rowland, J. J. Romeo, P. Romeo, P. Macnamara, E. Stucchi, S. Zufa, M. Vecchi, M. Salza Prina Ricotti, E. Gilotta, F. Becatti, G. Fabrini, G. M. Buonocore, M. 40 41 - Fuchs, M. - Buranelli, F. 42 43 - Piccarreta, F. - Liverani, P. 44 - Strazzulla, M. J. 45 - Franzoni, C. 46 47 48 49 - Scarpellini, D. - D’Alessandro, L., Persegati, F. - Milanese, M. - Scatozza Höricht, L. A. - La tipologia del banchetto nell’arte etrusca arcaica, 1961. - Osservazioni sul «Trono di Boston», 1961. - Umanità di Fidia, 1961. - Il commercio dei sarcofagi attici, 1962 - Sculture greche, etrusche e romane nel Museo Bardini in Firenze, 1965. - La cultura artistica delle province greche in età romana, 1965. - Il commercio dei sarcofagi asiatici, 1966. - Le antiche rotte del Mediterraneo documentate da monete e pesi, 1966. - I ritratti dei «cosmeti» nel Museo Nazionale di Atene, 1968. - Ritratti severiani, 1967. - Wiederverwendung alter Statuen als Ehrendenkmäler bei Griechen und Römern, 2a Ed. riv. ed. ill., 1969. - Bronzi orientali ed orientalizzanti a Creta nell’viii e vii sec. a.C., 1970. - Decorazione architettonica della «Piazza d’oro» a Villa Adriana, 1970. - Die Etruskische Plastik des v Jahrhunderts v. Chr. und ihr Verhältnis zur griechi-schen Kunst, 1972. - Studien zur Ikonographie der Antonia Minor, 1973. - Galba, 1976. - Porträttypen einer Claudischen Kaiserin, 1973. - Rappresentazioni dell’oltretomba nella ceramica apula, 1977. - The pre-Islamic Antiquities at the Yemen National Museum, 1978. - Ancorae Antiquae. Per una cronologia preliminare delle ancore del Mediterraneo, 1979. - Studi sull’arco onorario romano, 1979. - Aspetti di vita quotidiana nella Roma arcaica, 1982. - Archaische Statuetten eines Metapontiner Heiligtums, 1979. - Xoana e Sphyrelata. Testimonianze delle fonti scritte, 1980. - Torcello. Ricerche e Contributi, 1979. - Un’oicina lapidaria sulla via Appia, 1979. - Studi sulla città antica. Emilia Romagna, 1983. - Ritrovamenti romani in Sardegna, 1981. - Riuniicazione del centro di Roma antica, 1979. - Salvaguardia delle zone archeologiche e problemi viari nelle città, 1979. - Vita quotidiana degli Etruschi, 1982. - Il gruppo bronzeo tiberiano da Cartoceto, 1988. - Scritti di archeologia, 1982. - Torcello. Nuove ricerche, 1982. - L’arte del convito nella Roma antica, 1983. - Gutti e askoi a rilievo italioti ed etruschi, 1984. - Kosmos. Studi sul mondo classico, 1987. - Numana: vasi attici da collezione, 1984. - Schiavi e liberti dei Volusii Saturnini. Le iscrizioni del colombario sulla via Appia antica, 1984. - Il Teatro romano di Fiesole. Corpus delle sculture, 1986. - L’urna «Calabresi» di Cerveteri. Monumenti, Musei e Gallerie Pontiicie, 1985. - Manuale di fotograia aerea: uso archeologico, 1987. - Municipium Augustum Veiens. Veio in età imperiale attraverso gli scavi Giorgi (1811-13), 1987. - Le terrecotte architettoniche della Venetia romana. Contributo allo studio della produzione ittile nella Cisalpina, 1987. - Habitus atque habitudo militis. Monumenti funerari di militari nella Cisalpina romana, 1987. - Stele romane con imagines clipeatae in Italia, 1986. - Scultura e calchi in gesso. Storia, tecnica e conservazione, 1987. -Gli scavi dell’oppidum preromano di Genova, 1987. -Le terrecotte igurate di Cuma del Museo Archeologico Nazionale di Napoli, 1987. continued to page 180 MASSIMO LIMONCELLI VIRTUAL RESTORATION PAINTINGS AND MOSAICS With contributions by LAURA SCHEPIS AND CLAUDIO GERMINARIO «L’ERMA» di BRETSCHNEIDER Virtual Restoration. Paintings and mosaics Authors Massimo Limoncelli (M.L.), Laura Schepis (L.S.), Claudio Germinario (C.G.) Photographs Massimo Limoncelli, Laura Schepis, Claudio Germinario Cover photograph Laura Schepis Graphics Massimo Limoncelli, Laura Schepis, Claudio Germinario, Maria Potenza, Adriana Recchia, Cristina Balsamo Translation The text was written in Italian by the authors and translated into English by George Metcalf Progetto graico «L’ERMA» di BRETSCHNEIDER © Copyright 2017 «L’ERMA» di BRETSCHNEIDER Via Cassiodoro, 19 - 00193 Roma www.lerma.it - erma@lerma.it Tutti i diritti riservati. è vietata la riproduzione di testi e illustrazioni senza il permesso scritto dell’Editore. On the Cover: Patti (ME), Roman Villa, mosaic (photo L. Schepis) Massimo Limoncelli Virtual Restoration. Paintings and mosaics / Massimo Limoncelli (ed.) - Roma : «L’ERMA» di BRETSCHNEIDER, 176 p. : ill.,; 24 cm. - Studia Archaeologica; 218 ISBN 978-88-913-1575-5 (brossura) ISBN 978-88-913-1582-3 (pdf ) CDD 709.01 INDEX PREFACE (Richard Hodges) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » IX PRESENTATION (Norbert Zimmermann) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » XIII PREMISE (Massimo Limoncelli) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » XV I. VIRTUAL RESTORATION AND DIAGNOSTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » I.1. Virtual restoration of painted surfaces and mosaics (Massimo Limoncelli) . . . . . . . . . » I.2. Diagnostics and virtual restoration: surface analysis (Laura Schepis) . . . . . . . . . . . . . . . » I.3. Presentation of virtual restoration to the wider public (Claudio Germinario) . . . . . . . » 1 1 5 10 II. 15 15 17 22 27 34 SURVEY OF THE SURFACES (Massimo Limoncelli) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » II.1. Digital surveying and conservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » II.2. 2D photogrammetric surveying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » II.3. Surveying with a reference grid of iducial markers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » II.4. Camera scanner-based surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » II.5. Laser scanner-based surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » III. REPRESENTATION OF THE SURFACES (Massimo Limoncelli) . . . . . . . . . . . . . . . . . . . . . . . . . . . » III.1. Problems with representation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » III.2. Representations without distortion: lat projections and map projections . . . . . . . . . » III.3. Representations with distortion: perspective projections and 3D visualisations . . . . . . » III.4. Graphic scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » 39 39 40 56 64 IV. PREPARATION OF THE SURFACES (Laura Schepis) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » IV.1. Optimisation of the image and cleaning of the surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . » IV.2. Levels and Curves (bitmap graphics) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » IV.3. Black and white points (bitmap graphics) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » IV.4. Tone and contrast (bitmap graphics) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » IV.5. Exposure (bitmap graphics) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » IV.6. Chromatic alterations (bitmap graphics) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » V. MAPPING OF THE SURFACES AND NON-INVASIVE ANALYSES (Laura Schepis) . . . . . . . . . . . » V.1. Schematic mapping and quantitative analyses of decay . . . . . . . . . . . . . . . . . . . . . . . . . . » V.2. Thermographic mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » V.3. Infrared relectography and false colour mappings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » V.4. Mapping and qualitative analyses in xrf and raman spectroscopy . . . . . . . . . . . . . . . . . » V.5. Investigations by scanning electron microscope (sem) . . . . . . . . . . . . . . . . . . . . . . . . . . . . » COLOUR ANALYSIS OF THE SURFACES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VI.1. Perception, standardisation and measurement of colour (Massimo Limoncelli) . . . . VI.2. Sampling colour and chromatic correspondences (Laura Schepis) . . . . . . . . . . . . . . . . . VI.3. Analysis of colour (Massimo Limoncelli) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 69 71 74 76 77 78 81 81 86 90 92 95 VI. » 99 » 99 » 103 » 105 VII. TREATMENT OF THE SURFACES: LACUNAE (Massimo Limoncelli) . . . . . . . . . . . . . . . . . . . . . . » 111 VII.1. Lacunae: principles, forms of decay and digital intervention . . . . . . . . . . . . . . . . . . . . . . » 111 VII.2. Classiication and analysis of lacunae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » 115 VII.3. Reconstructable and non-reconstructable lacunae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » 118 VII.4. Filling in lacunae in monochrome – neutral retouching . . . . . . . . . . . . . . . . . . . . . . . . . . . » 119 VII.5. Mimetic Imitative pictorial reconstruction – total retouching . . . . . . . . . . . . . . . . . . . . . . » 125 VII.6. Imitative pictorial reconstruction – chromatic attenuation . . . . . . . . . . . . . . . . . . . . . . . . » 134 VIII. RECONSTRUCTION OF THE SURFACES (Massimo Limoncelli) . . . . . . . . . . . . . . . . . . . . . . . . . . » 141 VIII.1. Virtual iconographic reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » 141 VIII.2. Line-drawing reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » 142 VIII.3. Reconstruction of the "palimpsest" cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » 149 VIII.4. Virtual recomposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » 151 VIII.5. Stylistic reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » 162 BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » 169 To Giovanna and Marina PREFACE «A democratic civilization will save itself only if it makes the language of the image into a stimulus for critical reflection — not an invitation for hypnosis.»1 «..images have a productive quality that adds to and meaningfully transforms our archaeological practice. Indeed, upwards of fifty years of critical scholarly study of visual representation in archaeology testifies to the capacity of images to encourage us to rethink and reformulate interpretative approaches, add capital and methodological rigour to the field, inspire specialist and non-specialist audiences alike to alter our perceptions of material culture itself.»2 Images have informed the world since the Middle Palaeolithic cave art. Archaeology – too often the driest, most incomprehensible of sciences – can only be made comprehensible by reconstructions and models that bring language to a place. Reconstruction in some form or another of archaeological sites is not new. But globalisation and digital technology as Massimo Limoncelli shows in this eminently practical book demands new thinking about images, their manipulation and their social purposes3. Limoncelli builds upon a distinguished ancestry. Enlightenment painters were fascinated by Pliny’s fabled villa and by moments in time such as the fall of Rome to the Huns. From such reconstructions it was a short step to modelling sites as living places with the beginnings of scientific archaeology. Arguably the most influential master of the art of reconstruction was the British artist, Alan Sorrell, who learnt his craft alongside archaeologists at the British School at Rome in the late 1920s4. His reconstruction of Imperial Rome AD 330 has great sweep, yet projects a provincial metropolis within a brooding landscape5. By turns it is masterful in detail yet northern in its tremulous lighting and historical mystique. This mystique was to become the hallmark of Sorrell’s oeuvre, collaborating with the fabled giants of British archaeology – Sir Cyril Fox and Sir Mortimer Wheeler, to name but two knights of the realm. Sorrell’s images of fortresses and temples as well as bare prehistoric landscapes were the public images of the past and the frame for any study of archaeology. Through Sorrell’s pen the drama of discovery, for all its diligence, was transformed into a primeval world shaped to the spare parameters Preface IX of British modernist art. Like W.H. Auden’s poems, Benjamin Britten’s music and Stanley Spencer’s paintings, Sorrell’s images each invoked a burlesque within an insular Britain blessed by ravishing landscapes and a coveted heritage. Only with the end of this world in the 1970s and the beginnings of a neo-liberal professional archaeology did Sorrell’s work lose its status to a softer and, frankly, more nebulous imagery largely celebrating the state’s past. Sorrell’s work, as a result, like that of the pioneers of scientific and public archaeology, was consigned to history. Sorrell’s paintings, though, found echoes in many different countries. Popular archaeology magazines like Archéologie in France and Skalk in Denmark exploited reconstructions as compelling antidotes to underwhelming narratives about archaeological sites. Was the echo of Sorrell’s work to be found in Italy also? An early advocate of archaeological reconstruction was the artist, Paolo Donati with a proven background in cartoons, fumetti. Working with the Sienese archaeologist, Riccardo Francovich in the early 1990s, Donati’s lasting achievement is a limpid painting of the Medieval hilltop mining village of Rocca San Silvestro, Tuscany6. Set in a pale blue haze, Rocca viewed through an eagle eye was vividly brought to life. Donati then developed the concept with collaborators who formed Studio Inklink, based in Florence. Operating as a small collective, Studio Inklink produced paintings for site information panels and book illustrations. Their working method was labour-intensive and involved experimenting with early forms of digitisation. Using photographs and archaeological drawings, they made accurate detailed sketches. Following this, computerized elements were introduced to obtain the three-dimensional scope of a scene or a structure. The 3-D skeleton provided the outline of the mass of a monument in its context. Then, drawing on their experience as cartoonists, lithe figures and nimble action were introduced to the sketches. Colouring the sketch involved traditional methods, with delicate brushwork and, as often as not, the thoughtful deployment of ochrous textures. As many as four or five artists worked on one painting, reaching a shared vision which was digitized for site or museum use. Inklink made their name in Tuscany. Numerous archaeological parks dotted around the western part of the regione still boast Inklink panels. Their artistic treatment owed much to the late 20th-century world of Italian design and was the sum of proficient Italian archaeology and technology blended with a strident Italian sense of the visual. Studio Inklink belong to their age and place: their time based on expensive working practices had passed by 2010 and in 2017 belongs to the historiography of Italian archaeology as much as Alan Sorrell. Their place was taken by full digitization. - computerized virtual reality. The new world order is irresistible and with social networking comes the need for hyper imaging of an entirely different order of magnitude. As Limoncelli skillfully shows this digitization proffers an exactitude and plasticity for our era. X Richard Hodges Neither Sorrell nor Inklink granted us a description of their techniques; theirs were personal practices now more or less lost to time. But this book is different. Massimo Limoncelli is a master who is gifting his peers a manual. In eight fabulously illustrated chapters he describes how to scan and then work the virtual into all manner of monuments. The laser scanner is his preeminent instrument, but his eye and the discipline of his craftsmanship are no less important. Most of his 38 cases are from churches or Roman sites with pavements in the Salento, a region blessed with antiquity. In each case the fragment is carefully re-created as though it was the authentic original. The result is authentic, indistinguishable from the fragment, yet a record that is both powerful for the public to help comprehend the painting, for example, and a massive stride forwards for students of art history and archaeology who need to understand the place of the fragment in its original form. The manual takes the reader through pavements, walls punctured by high windows, apses and cupolas but in truth it is the brilliance of the result that dazzles. The author’s supreme point is that this tool is no longer the remit of the individual but the property of a new world order. It can be replicated and with pleasure. My personal favourite is the Crypt of the Original Sin near Matera. Limoncelli’s reconstruction published in a ravishing account of these 9th-century frescoes is pleasingly satisfying7. This place is as sublimely dazzling as the Sistine Chapel, and paradoxically a lot more comfortable to visit. Of course, this is not a crypt, and it has nothing to do with Byzantium, as much of the local literature suggests. Painters from Beneventan Principality transformed this small mid 9th-century church, possibly for funerary purposes, providing it with indisputable iconographic echoes of painting in Rome. Nevertheless, in visual conception, with imagery that leaps from codices of the time, it was clearly the work of someone living on the frontier with a resurgent Byzantium keen to demonstrate his ideological loyalties. Here, thanks to these virtual reconstructions, we might imagine pilgrims paused in yet another riff on purgatory before traipsing southwards towards the Byzantine port of Otranto, where they then took a ship to the Holy Land. Limoncelli is the first to provide us with a text to his artisanal gifts, but not the first to demonstrate the importance of virtual reality for our times. One example is close to my heart. Inexplicably shut for decades, S. Maria Antiqua is the secret jewel of Rome’s Roman Forum. In 2016 it re-opened courtesy of new digital arts. S. Maria Antiqua’s best-known paintings are the fragmentary frescoes in the apse and flanking side chapels. In the Chapel of the Medical Saints to the east of central apse, using simple projection, the original decoration dating to Pope John VII (705-7) is skillfully reconstructed. More striking still is the darkened Chapel of Theodotus to the west of the main apse dating to Pope Zaccariah (741-52). Here, the full floor-to-ceiling ornamentation of the chapel comes briefly to life before your eyes including the host of figures and the dados decorating the lower register of the chapel’s walls. A sePreface XI quence of episodes describes the martyrdom of Quiricus and Julietta; the southern panel depicts an enthroned Virgin with Child alongside Peter, Paul, Julietta and little Quiricus, the donor himself – Theodotus and Pope Zaccariah. The museology reinstates the glory of this complex monument, and above all is a feast for those who want to understand the roots of High Medieval and Renaissance art. Rome under the popes was a melting pot of creative ideas, brought here from Byzantium as well as all parts of Italy and the northern Christian kingdoms. It is true to say that nowhere in Europe boasts such visual riches from the Dark Ages. Now using the tools that Limoncelli describes in this book, other treasures can be made accessible to the public, helping us as Sorrell and Studio Inklink did to bring common support to care for our patrimony. Limoncelli’s book is a practical and clearly written guide to the imaging that will help to put the past back into the heart of Europe’s cultural patrimony. Brilliant in every sense, matching technology to skills means so many monuments and treasures can be enjoyed as the case of S. Maria Antiqua so wonderfully illustrates. New technologies will arrive to outmode those described in this important manual, but the scanning platform from which Limoncelli operates belongs to our new world order and marks a paradigm shift far greater than perhaps we yet appreciate in critically reflecting upon the past. RICHARD HODGES The American University of Rome Rome, May 2017 NOTES 1 ECO 1979, p. 12. PERRY - JOHNSON 2014, pp. 223-52 at 324. 3 See also LIMONCELLI 2012. 4 Ib. 5 Ib. fig. 2. 6 HODGES 2011, pp. 109-11. 7 BERTELLI – MIGNOZZI 2013. 2 XII Richard Hodges PRESENTATION When dealing with the world of virtual reconstruction and the possibilities offered by new technologies and especially computerized animation, one is left speechless at how easy it is to generate attractive, fancy, indeed, astonishing reconstructions featuring surfaces that are photorealistic to the point of being flawless. Nevertheless, the most important aspect from a scientific point of view is to be aware of the responsibility that one shoulders when creating such images: once an image is out in the world, it is difficult to erase it from the memory of the ‘viewing public’ if one attempts later to establish visual versions of a reconstructed past that are more realistic but less eye-catching and less ‘flawless’. A second, but no less important, aspect has to do with terminology: a reconstruction should broadcast the fact that it is based on the scientific study of fragmentary remains and thus represents one possible solution to an archaeological and architectural puzzle, rather than being a matter of mere fantasy or ‘fantascienza’; in such cases we should clearly say that we are talking about a hypothesis of reconstruction. But even if the learned community is sensitive to such definitions and reflects on their differences, the wider public generally is not sensitive to them and will not keep them in mind. What the public will keep in mind is the visual reconstruction. As already said, it is like Pandora’s box: the more flawless and eye-catching an image, the more difficult it is to correct it once it is out in the world. From this point of view there are two advantages of this book: first, it carefully introduces the reader to what is possible today in the world of 3D and computer-based animation and reconstruction, and in the process, trains the reader to understand what lies underneath the (sometimes excessively) beautiful surfaces that are increasingly the standard in visual media. And second, it shows how scientific reconstruction is based on a laborious and very detailed process of differentiated scientific work, with a long history of its own before any kind of computerized reconstruction or animation entered the picture. In this context, as so often, less is very often more -- but when we do decide to show more, every visible aspect should stand up to scientific scrutiny. NORBERT ZIMMERMANN Deutsches Archäologisches Institut – Rome Rome, May 2017 Presentation XIII PREMISE In a previous work on the general theme of Virtual Restoration in archaeology published in 2012, I sought to provide a complete summary of this new discipline, which is now becoming progressively more important in the study and recovery of Cultural Heritage. A few years later, it has become necessary to update and expand a number of concepts and methods applied to Virtual Restoration, particularly regarding painted surfaces and mosaics. The idea of combining in a single volume the virtual restoration of mosaics (which in real restoration fall within the category of stone artefacts) together with paintings, be they on canvas, wood or walls, derives from the fact that in a virtual environment mosaics share all the methods of investigation and intervention of pictorial restoration. Indeed, a mosaic can also be considered «a sort of “painting”, the most long-lasting that can be found, considering that painted colours fade with time». The term “painting” on the other hand indicates «a surface covered in various colours, on a wall, a wooden panel, a canvas and so on, which by virtue of lines, shadows and lights and a good design, shows the figures fully rounded, detailed and foregrounded». Both are decorative techniques used for covering floors, walls, ceilings and architectural and sculptural elements. Mosaics are made up of fragments of natural stones, terracotta, vitreous paste, marble or enamel, black or coloured, applied to a specially prepared surface in mortar and arranged to form geometric or figurative designs. Painting on the other hand, regardless of the type of support, is the artistic representation of volumes, persons and objects, by means of lines, colours and tones. In order to examine all the themes relative to the virtual restoration of paintings and mosaics, the book is divided into eight parts, with 38 case studies dealing with specific issues: from the survey of the surfaces to their representation, from the mapping of decay to the analysis of the pigment, from the treatment of the missing parts to their virtual reconstruction, and the diagnostic analyses of the surfaces. This volume, the fruit of a decade of work, has enabled me to bring together and publish a number of virtual restoration projects conducted by myself and students attending the course in Digital Restoration and 3D Restitution as part of the Degree in Conservation and Restoration at the Accademia di Belle Arti in Lecce, which I had not previously had a Premise XV chance to present. Many of the case studies illustrated here concern the medieval frescoes of Puglia and Basilicata, as well as palaeo-Christian and late-ancient wall paintings respectively in Rome and Hierapolis in Phrygia (Turkey), while others concern mosaics in Sicily, Calabria and the Salento peninsula. The publication of this volume was made possible by cooperation with my friends and colleagues Laura Schepis and Claudio Germinario. I would also like to take this opportunity to thank all those who have contributed to the creation of this book, especially Enrico Caruso, Director of the Selinunte Archaeological Park and Cusa Quarries, and Gabriella Tigano and Rocco Burgio of the archaeological authority (Soprintendenza) of Messina, for having allowed me to study the mosaics of the Lylibeum Archaeological Park (Marsala) and the Roman villa of Patti (Messina), and Francesco D'Andria, director of the Italian Archaeological Mission at Hierapolis di Phrygia. I also thank the students at the Accademia di Belle Arti in Lecce: Cristina Balsamo, Maida Leo and Adriana Recchia, whose hard work has helped to enrich the contents of this book. Lastly, I thank Francesco Nelson Russo, Filippo Pisciotta, Raffaele Franco, Roberto Miccichè, Pietro Valenti, David Scahill, Maria Potenza, Giuseppe Donvito, Roberto Rotondo, Tommaso Ismaelli, Piera Caggia, Giuseppe Scardozzi, Lucinia Speciale, Marina Falla Castelfranchi, Manuela De Giorgi, Gioia Bertelli, Martin Mohr, Christoph Reusser, Mario Capasso, Paola Davoli, Richard Hodges and Norbert Zimmermann. Maybe they do not know why, but I do! Finally, my greatest thanks go to Luana Toniolo. MASSIMO LIMONCELLI Lecce, May 2017 XVI Massimo Limoncelli I VIRTUAL RESTORATION AND DIAGNOSTICS I.1. VIRTUAL RESTORATION OF PAINTED SURFACES AND MOSAICS The term restoration is traditionally defined in the studies as all operations necessary to restore an artefact to its initial condition, assuming that this has been compromised by wear and tear or traumatic events. Restoration is aimed at the aesthetic recovery of works associated with the taste of individual epochs and derives from the Latin term restauratio, which indicates renovation, refurbishment and recovery. Its purpose is "restitution", understood as repair, replacement of missing parts, refurbishment, recontextualisation or reconstruction in order to restore a given item to its primitive state or supposed splendour1. According to Cesare Brandi, restoration entails «the methodological moment of recognizing a work of art in its physical composition and its dual aesthetic and historic polarity, in view of its transmission to future generations»2. Currently, modern scientific restoration entails eliminating as far as possible the causes of decay and restoring the legibility of the artefact’s historic evolution. Restoration thus represents an attempt to slow pathological processes of decay that cannot otherwise be tackled in any other way3. Specifically, during pictorial restoration, «it is not a case of refreshing the colours or restoring them to a hypothetical and unverifiable primitive state, but of ensuring the transmission to future generations of the material that gives rise to the concreteness of the image. Nor is it about regenerating them, of reproducing the technical process by which the paintings were originally executed […] A fresco is not restored by repainting a fresco, a tempera by repainting a tempera, an oil painting by repainting the oil. Whenever this is performed, a serious error is made. […] Restoration is performed, if at all, without replacement of missing parts, and in all cases the repairs and replacements must be recognisable to the naked eye»4. Today, the use of digital applications in the field of restoration has opened up new possibilities for research thanks above all to the transVirtual restoration and diagnostics 1 formation of information technology from a support for the management and documentation of data to a tool for their production and analysis. In the beginning, information technology was used mainly for digital cataloguing and archiving, as part of the management of data concerning national Artistic Heritage. Only in the late 1970s did restorers begin to notice the potential of applying the nascent technology to restoration, above all pictorial, since it made it possible to carry out interventions on materials and colours whose effectiveness could thus be verified scientifically with an electronic computer5. Indeed, using a system for acquisition and conversion of images into a digital format, it is possible to perform accurate quantitative assessments. In the mid 1980s researchers became fully aware of the potential of information technology «not only for cataloguing cultural heritage items but also for determining the state of conservation of the works of art and for operations considered to be generally linked to the artistic sensitivity of the restorer, such as the replacement of missing sections of paintings»6. The mid 1990s saw the emergence of the concept of "Electronic Restoration"7, followed by "Virtual Restoration", understood as the sum of integrated Computer Graphics methods, both two- and three-dimensional, used for the representation of an archaeological, architectural or artistic item in its complete, or almost, integrity8. Ever since the definition of "Virtual Restoration" was proposed, a terminological debate has raged over the association of two words that appear contradictory: “restoration”, understood as an action that entails a transformation, both morphological and material, of an artefact from the state previous to the intervention to the state following it, and “virtual”, which implies the very opposite of something material, visible and concrete9. However, while on one hand «the decision to match the two terms “virtual” and “restoration”, arising from the synthesis of technique and objective»10, may have seemed effective, on the other hand, certain theoreticians of restoration considered it to be an "oxymoron". This is because they baulked at using the term “restoration”, albeit virtual, to refer to «a technique that was performed on the image of the item and not on the original, and thus had neither the characteristics nor the purpose of material restoration»11, whose proper objective was to act on the material of the work in order to restore its functionality, aesthetics and durability over time. In reality the lexical debate over virtual restoration is «a terminological polemic that no longer seems relevant today, if one considers the contribution that the idea of performing on the image of the item all the information recovery measures that cannot be performed on the original has made to resolving the issues of safeguard and promotion of heritage»12. Virtual restoration combines all the applications and potential of virtual reality as applied to Cultural Heritage with the methods, rules and prin2 Massimo Limoncelli ciples of conservation and real (or traditional) restoration from which it springs. Virtual restoration represents a non-invasive method for digitally previewing real restoration measures on the actual works and fully falls within the concept of safeguard as mentioned in Article IV of the Italian Restoration Charter of 197213. It was precisely at that time that virtual restoration began to establish itself as an autonomous discipline within the domain of Cultural Heritage, at the conclusion to a journey that represented the «evolution of an idea, arising from a powerful curiosity, which emerged by chance from an unplanned intuition and developed till it became an innovative and consolidated practice»14. Precisely because it acts within a virtual environment, virtual restoration is able to answer a number a series of questions regarding the theory of real restoration. These include the thorny problem of whether to «conserve or modify (restore) the data that are historically embedded in a work of art or an ancient object»15 and the problem that accompanies and precedes any restoration measure, i.e. when to intervene on an artefact and above all with what techniques. «The artefact no longer adequately serves the functions for which it was created, so it is necessary to restore it. […] It is necessary to ensure its survival as a physical object, intervening on its constituent materials. The extent of this intervention varies firstly depending on the current state of the artefact and secondly on the objectives to pursue. Thus it may be limited to simply maintaining the state in which the artefact came to us, because nothing more can be done. […] At the other extreme, if the conditions of the artefact allow, it can include the full recovery of its original functions. […] Between these two types of intervention, i.e. between minimal conservation and enhanced restoration, there is a whole range of possibilities, which means that every conservation or restoration measure represents an individual case, not repeatable in series»16. The objective of virtual restoration is the restitution of a work’s formal unity, i.e. as it would appear after a physical restoration. By simulating the various phases of intervention it is possible to provide tools that help prefigure the final result, in accordance with the principle of guided restoration, i.e. providing all the knowledge that may be useful for planning the real intervention. This implies another principle: «physical restoration to conserve an item and virtual restoration to educate»17. In this sense, virtual restoration aims to reconstruct the appearance of the artefact «at the moment of its creation»18, following an approach that can be called “mental restoration”, i.e. «an attempt to reconstruct the presumed original state using only critical and philological tools, without actually touching the work. This is because, at the end of the day, the debates and the historical, critical and aesthetic hypotheses lend themselves more to discussion and to written and drawn working hypotheses than to experimentation on the ‘corpus’ of works themselves»19. Virtual restoration therefore makes it possible to optimise the legibility of the work without recourse to irreversible intervention on the Virtual restoration and diagnostics 3