Proceedings of the 1 st lnternational EARSeL Workshop CNR, Rame, September 30 - October 4, 2008

Advances on Remote Sensing for Archaeo/ogy

and Cultura/ Heritage Management

Edited by Rosa Lasaponara

Nicola Masini

CD-Rom included

Published tor : EARSeL - European Association of Remote Sensing Laboratories CNR - IMAA (Istituto di Metodologie di Analisi Ambientale) CNR - IBAM (Istituto per i Beni Archeologici e Monumentali)

Cover design: Nicola Afflitto (IMAA-CNR)

Disclaimer: the Editors and the Publisher Aracne Editrice S.r.l. accept no responsibility tor errors or omissions in the papers and shall not be liable tor any damage to property or persons arising from the use of information contained herein .

Published and distributed by Aracne Editrice s.r.l. via Raffaele Garofalo, 133 A-B, 00173 Rome, ltaly. T. +39 (0)693781065, www.catalogoaracneeditrice.eu

Copyright © MMVIII ARACNE editrice S.r.l.

ISBN 978-88-548-2030-2

No part of this book may be reproduced in any form, by print, photoprint, microfilm, microfiche, or any other means, without written permission from the pub/isher.

1" edition : September 2008

F. GADELLONE. I. Ft:RRAKI. F. G1t:RI er al.· lmegrared 3D merhods /or <1 DVR-based J.noll'ledge p/alfon11 257

Development of integrated 3D methods for the creation of a DVR-based knowledge platform

F. Gabellone, I. Ferrari. F. Giuri, M. Limoncelli

IBAM ITLAIJ, CNR Consiglio Na-;:,io11ale delle Riterr/1e, Lette, 73 100, lraly.fgabel/011e@iba111.cnr. it

Keywords: Virtual Reality, Laser Scanning, Distance Visiting, Desktop Virtual Reality (DVR)

ABSTRACT

This study is onc of 1hc ac11v111cs organised as pan or the ByHeriNet project ("Byzaminc Hcritage Network: Rehabilitation. highlighting and management in the Eas1cm Mcditerrancan Basin'"). promotcd undcr the EU Programmc known as INTERREG lii B .. ARCHIMED". Thc main objcc1ivc of thc ac1ivi1ics of the lbam lTLab wi1hin the ByHcriNet projcct is Lhc devclopmcnt of intcg rated mcthod f> for thc creation or 1hrec-dimensional models using laser scanning techniques. digitai photogramrnctry. 30 pho1omodelling and dircct survcying. applied 10 Byzantinc sites in thc province of Lecce and thc region of Basilicata in thc South or haly. The thrcc-dimcnsional modcls cstablishcd using thcse melhods constitute an advanccd inrorma1ion pla1form, able to rcprc cnt 1hc archilcctural morphology or the huildings under study with grea1 accuracy at various scalcs, including hoth dc1ailcd clcmc111s and 1hc monumcn1al arrangcmen1 as a whole, as well as 1hc tcxtural fea1urcs or thc internal and cxtcmal surfaccs. Thc main airn of lhis Mudy i 10 cnablc thc public to enjoy the resuhs of archacological and archaeornctric rcsearch, via thc wch or stand-alone products. and to "vinually visit'' thc rnonuments using RealTimc 30 visiting syslcms. The navigation platforrn allows Lhc user to visualise complex sccnes and DVR-bascd knowlcdgc models in "full- crcen mode" cvcn on desktop cornpu1crs. As wcll as showing thc currcnt state of thc monurnents, Lhc visit inc ludcs rcconstructions of prcvious phascs in thcir his1ory and vinual rcstorations of thc Byzantine paintings. Ali thc tcxturcs wcrc ohtai ncd by proccsses of photomodclling and wcrc applicd to 1hc geometrica) fonns in accordancc with 1hc radiosity algorithrn, with ligh1s and shaclows of 1hc ·arca' typc. Thc rcsult is cxtrcrnely life-likc. almos1 indistinguishahk from rcality.

Figure I: 30 restit11tio11fro111 laser sra1111i11g ali{/ Camera mapping of Madonna delle Croci t h1m·h (Matera. ltu/y).

I . OBJECTIVES

The main objec1ive of 1he Jtalian National Research Council 's fbamlTLab in lhe contex1 of 1he By-HeriNet project is 1he development of integrated methods for the creation of three-<limensional models using laser scanning 1echniques. photogramme1ry and 30 photomodelling, applied to Byzantine sites in 1he province of

258 6. 30 visuali1.a1ion and virtual rcconstruction of landscapc and site.•

Lecce and the region of Basi licata. wi th particular reference 10 those monuments with elemenls of special interest that are represenlative of the period in question.

The three-dimensional models developed using the integrated methods described below provide a use-fui knowledge base for representing architectural morphology on various scales with great accuracy. This includes both specitìc details and the overall monumental ammgement, as well as Lhe textural characteristics of the interior and exterior surfaces.

Each monument was modelled and studied in relation to irs envi ronmental context. noting its underly-ing system of relationships. which is often the key to understandjng the architecrural strategies adopted. The main goal of this research however remains that of allowing the public to benetìt from the results obtained, either via the web or stand-alone products, so that they may "visir'' and enjoy the monuments u ing both 3D RealTime visiting systems and spherical and interactive 3D panoramas. Each three-dimensionaJ model is thus integrated in a multimedia authoring system in which ali the data forrnats avai lable for the item in question (audio, video, VRML, QTVR, VR-Object, images, ta-bles. etc.) can be combined in a single environment. Descriptions of an academic and criticai nature (historical overview. relations with other ancient contexts, exegetical analysis, etc.) are combined with technical and scienti tic methods of analysis and diagnosis (e.g. analysis of consti1Uenl materials. state of conservation, study of architectural characteristics. ere.).

In an interactive environmenl, it is possible 10 interact with the structures of the sites under study and search rhe associated Databases for drawings of the layout, topographical data, orthophotos and his-torical documents. together with informarion on the mineralogica! and pctrographic characteristics of the construction materials, plasters and paintings. The virtual visit is funher enriched with CG (Com-puter Graphics) reconstructions thai provide the user with a diachronic reading of the monument and enable him/her to beuer understand the transformations il has undergone.

Tue process of creating conteni relating to each monument studjed may be summarised as follows:

I . Gathering of the historica I documentati on ava i lable;

2. Architecrural survey of the structures, performed with methods appropriate to the distinctive charac­teristics of each monument:

3. Three-dimensional reslitution and optimisation of the models in accordance with the predicted out-puts;

4. Extraction of the two-dimensional maps and video footage to be integrated in the computer vision systems or in the stand-alone publishing products (DVD Videos. VRML models. etc.)

5. Creation of virtual sphericaJ panoramas (QTVR);

6. Implementation of rhe 3D models and QTVR conuibutions in VR knowledge platforms.

3. FIRST CASE STUDY: THE ABBEY OF S.M. DI CERRA TE

The Abbey of Santa Maria di Cerrate. situated in open countryside in the municipality of Squinzano, a few kjJometres North of Lecce, was founded at the beginning of the 12•h century by Norman counts.

The aims of the architectural survey of the Abbey of Santa Maria di Cerrate are Lo document the currenl state of Lhe building and construct the three-dimensional models necessary for the development of the knowledge platforms described above. Consequemly, the survey operations concemed not only the individuai surfaces of the church itself, but aJso the series of bui ldings thal encircle the Abbey today in a "defensive wall" and forrn an inseparable pan of the same monumenral complex. Given this premi se, the early phases the work focused on the acquisition of the basic photographic documentation and on the choice of appropriate techniques for the restitution of the monumentaJ complex at a high level of detail and precision. As already mentioned, considering the ajms of the communication produccs and the survey issues specilìc Lo this case, il was readily perceived tbat tbese requirements could be met by restitulion techniques based on digitaJ photogrammetry and photomodelling in panicular. The reasons for this choice obviously include their greater flexibility and ease of use compared 10 normai photogrammetric Lechniques. but above all lhe possibility they provide of obtaining three-dimensional models of great precision at very low cost (rif. Low cost met, CIPA). In this specifìc case. it should be stressed that the surveying difficulties resulting from the heigh1 of the buildings. together with the problems of accessibility Lo cenrun architecturaJ elements (the rose, roofs. upper window . etc.). mean that considerable effort (and additional costs) would have been required for the deployment of of the equipment necessary fora rraditional photogrammetric survey. Given the conditions. the adoption of a systcm based on laser scanning was also excluded a priori, in thai this would have required greater processing times in terms of post-editing and would have generated redundant data for the flat surfaccs. In an archi1ec1Ural survey with specific ajms such as this one. the key factor is rhe criticai judgement of the surveyor, who mu t identify. by

F. GABEl.LO~E. I. FFKKAKI. F. Gll RI et (I/. · l111egr<11td JD metluxls /or n DVR-/J(lsed kn<Jll'/edge p/(l{jorm 259

means of a careful analysis of the archi tectura l elements. only the essential points necessary for the restitution. This criticai evaluation. which entails the recognition of corresponding points in different photographic shoots. is also 1he fundamen1.2l task in photomodelling surveys. In operational tenllS. it is suffìcient 10 identify the venice of each architectural elenient. or insen some iargets on 1he surface being surveyed in the poorly charac1eriscd areas. in order to obtain three-dimensional models complete with textures mapped in UVW projection.

4. SECOND CASE STUDY. THE RUPESTRJAN CHURCll OF MADONNA DELLE CROCI

Entrance 10 the crypt is through a round arch wich a simple rectangular door in the centre of a semicir-cular façade carved in 1he rock which contains a series of niches and engraved crosses. The interior. rectangular in shape and oriented East-West. is subdivided imo two vauhs separated by a segmentai diaphragm arch. Each vault is supponed at the sides by blind arches where. in 1he vauh closest to the emrance. numerous crosses are engraved.

The survey of the internal walls of 1he crypt was pe1forrned wi1h an time of flight laser scanner. The acquisition was based on domes of abou1 six metres in radius. with a level of detail of the point clouds of 2-4 mm. Fi ve scans were necessary. three in ide and two out ide, 10 describe the entire item with a good coverage of the undercu1s.

The scanner proved 10 be fasi and reliable, but the editing of the point clouds required a considerable effon on the pan of the operator to resolve problems caused by exponing in the dxf format, which resulted in pronounced anomalies and discominuities in horizontal bands al regu lar intervals. In each case the manipulaiion of the meshes using software dedicated 10 the management of point cloud resolved the problem sa1isfac1ori ly. and the results are visible in the images hown in this anicle. The polygonal mesh was subsequently decirnared in order to maintain the number of polygons within a limit that was empirically tested on normai consumer computers. in the order of 400-500 thousand polygons. In 1he texturing phase, thi limit. imposed for reasons linked to the perfom1ance of the Realtime engine. considerably implifìed the selection of 1he groups of faces to which each individuai materiai was assigned. The internal walls were mapped using the Camera Mapping method. well-known and used in cinematography, but rarely used in other applications such as the restitution of monuments.

Our experience ha. shown che excellent performance of CM on curvcd surfaces. for example the apsidal wall or the underside of the arches of the lateral walls: on ali the 01her surfaces an cxtensively subdivided planar projection was used. again to limit distonions in the undercuts as much as possible.

Figure 2: A sr reenshot of DVR platform with his navigation interface. lnteriors of S. M. di Cerrate abbey.

260 6. 30 visunlinnion and virtual rccon,1ruc11on of land.,capc and '-Ile'>

Figure 3: 30 re:sti1111ion/rom photomodellillg <1ppro<1clt o/S. M<1ria ,/; Cermte abbey.

REFERENCES

Lévy P. 1997. // Vimwle, RaffaclloConina Editore. Milano Fonscca, C.D., Roubis. D., Sogliani. F. 2007. iure Vetere. Ricerrhe archeologiche 11el/u prt111a fo11da::;io11e monastira di

Gioacchino da Fiore (i11dagi11i 2001-2005), Sovcria Mannelli. Gabcllonc. F .. Gian11011a. M.T. 2005. Rea/time Jd multimedia system fo r the dista11ce 1•isiti11g of c11lt11ral heritage. Il

case s111dy 011 the rhamber 10111/Js i11 1•ia Crispi, Tara1110. XX CJPA lntcrnational Symposium. lntcrna1ional CoopcraLion to savc Cullural Hcritagc. Torino.

Gabcllonc. F .. Giannoua. M.T. . Monte A. 200 I. Nurbs Model/i11g for the co11sen·atio11 of a11cie111 811ildi11g1-, i11 211d /111emmio11al Congress 011 S111dies i11 A11rie111 Struc111res. btanbul 9- 13 Jul y.

Rossi, M .. Salonia, P. 2003. Co1111111ica::;io11e 11111/1i111ediale per i be11i c11/t11rali, Addi~on Wcslcy. Milano.