REAL-TIME INTERACTIVE RECONSTRUCTION OF ARCHAEOLOGICAL LANDSCAPES: AN OPENSOURCE APPROACH FROM GIS TO VIRTUAL REALITY L. Calori a, M. Forte b, S. Pescarin b a
b
CINECA, Supercomputing Center, via Magnanelli 6/3, Casalecchio di Reno – BO, Italy - (
[email protected]) CNR ITABC (Institute of Technologies Applied to Cultural Heritage), via Salaria km 29,300, 00016 Monterotondo St. (Rome), Italy ([maurizio.forte],[sofia.pescarin]@itabc.cnr.it), www.itabc.cnr.it/VHLab
KEY WORDS: Virtual Heritage, Landscape Reconstruction, Terrain Generation, Web application, OpenSource ABSTRACT: The development of 3D real-time visualisation of geographical data (GIS and remotely sensed data) allows today the use of DVR (Desktop Virtual Reality) systems not only to communicate final results of scientific studies, but also for the process itself of analysis, interpretation and reconstruction of archaeological landscapes. The paper will be focused on a new approach based on OpenSource projects that, we believe, can produce positive results in the field of Cultural Heritage, and most of all of Virtual Heritage. Some testing cases will be discussed on the generation at different levels of detail (LOD) of territorial data, on the interaction with the archaeological landscape of the Appia Antica Park in Rome and on the publication of the three-dimensional landscape over the Web, based on OpenSceneGraph and Virtual Terrain Project.
INTRODUCTION Introduction. The digital revolution If we analyse last years trend in the field of Geographical Information Systems, we can clearly notice how wide has become the interest towards 3D visualisation; most of the software packets have added or implemented 3D extensions. On the other side computer games are spreading off quite rapidly. Almost the entire new kids generation (in Europe, US and in many parts of Asia) knows and tried a computer-game or possesses a ‘playstation’, ‘x-box’ or similar: real time Computer Graphics is becoming a common experience part of everyday life. Behind this, there’s surely a component connected with entertainment, pushed by a strong economic interest. Other sectors can hardly obtain the same kind of investments, although the research activity and the philosophical theorisation already have indicated, in the last decade, some potential future developments that could possibly change the approach toward cultural information (Barcelo, Forte, Senders, 2000). Archaeology, History, Art fields started their first experience in computer-graphics and 3d visualisation in the ‘80s. Our experience, of CNR ITABC and CINECA Visit Lab, has got through many phases before reaching to last applications on Desktop Virtual Reality Systems (Calori, Guidazzoli, Forte 1996, Forte 1997; Forte et alii 2000). Although the revolution of digital technologies is commonly treated mainly from a technological point of view, we would like to underline the importance even of a cultural point of view. We believe in fact that Virtual Reality systems could be an answer to many questions, increasing their application (in quality and quantity) in the next years to many fields, but with a strong theoretical epistemological discussion. We would like to discuss about technological issues according to an ecological and cybernetic viewpoint (Maturana, Varela, 1980, 1987;
Bateson, 1972; Forte et alii, 2001). We believe, indeed, that the Virtual, first of all, is an environment and an ecosystem. According to an ecosystemic perspective the Virtual represents a complex of relations, an ecosystem. The virtual translation of heritage is explainable according to a connectivity of information creating a system. According to this methodological approach the information processing correlated to heritage is able to modify its interpretation, its value. We could say that the last goal of the digital processing is the perceptive and cognitive increasing of the thing-cultural heritage, digital access to the virtuality (then with feedback) of the cultural information. Virtual Heritage, and in particular archaeology, presents often interesting case-studies due to their complexity and to the strict needed connection with spatial (and temporal) components. Landscapes and sites (at a macro and micro scale) can be treated as perfect interfaces with cultural information, perfect connectors among cultural objects, time-components, contents, spatial information, diachronicity, social and anthropological aspects. With a VR system it’s possible to access even complex contents very easily, to assemble different data and experience them, to recreate lost contexts, to reflect over historical topics as over anthropological ones. Unfortunately the story of last decades CG applications in the field of Cultural Heritage is a story of powerful reconstruction environments, with no behaviours or interactions apart from the movements of the user inside the 3d space. These applications were visible just on expensive workstations, not accessible freely by a public users, but they were driven by a human operator. In most cases they have been accessed, especially in the case of real-time VR, only by small communities, remaining inside laboratories, universities, computing centres. And this is today almost unacceptable if we think the investment required for such VR systems compared to Cultural Heritage general economical policy and to effective benefit of these reconstructions.
The distribution of cultural information is surely a key-issue for the future of the knowledge of Cultural Heritage, that will be committed to new complex systems, different from the traditional linear systems. A crucial problem indeed is the transmissiblity of more and more composite information, through complex VR systems that need to be studied by interdisciplinary and international teams in term of communication and interfaces. The research, but also the worldwide community, require more interactive systems, more dissemination and data sharing possibilities, step by step information control, updatable and open systems. Ancient Landscape Reconstruction Virtual reality systems, thanks to data integration potentialities, can re-create connection between information and create new information. The possibility to compare data and information allows an increasing of the knowledge (Bateson, 1972). So in order to obtain a spatial Virtual Reality System we have to make data ‘comparable’ in overlay, keeping its spatial component. A GIS project has to be constructed at the bottom of any further project development. Even Databases have to be possibly planned in connection with vectorial and spatial information, while 3D models can be modelled even apart, but with particular attention to their geographic position and to their use for real time and web publishing purposes. Inside the Geographical Information System data are prepared to be used in the VR application: DEM, Geoimages and Vectorial thematic layers (Culture). Keeping data spatial component allows, even inside a VR system, to do some spatial analysis, creating new interpretations and new information. This information can be used to update the GIS, as new thematic layers, in a sort of “virtuous circle”. What we obtain is a Virtual Reality application based on a Geographical Information System, characterized by the possibility of sharing data, exchanging information, testing different reconstructions and revising data (Fig1).
real time spatial virtual environment. Thanks to this kind of tools it’s possible to maintain the complete spatiality of the data (Forte et alii 2003). On the other side the use of software, personalized (such in the case of VirTools) or appositely created and programmed (VISMAN: Calori et alii 2003, Calori et alii 2004), to visualise and interact with those data, directed us to a development in the realisation of complex VR applications. The reconstruction of a landscape, present past or even future landscape, can be achieved through different steps: 1. study of the content 2. processing of a GIS project 3. processing of one or more Virtual Reality projects; this step includes even: terrain generation, 3d modelling, database and multimedia resources creation. 4. realisation of a VR application characterised by a certain number of behaviours or interaction inside the VR environment (VISMAN/VIRTOOLS).
Figure 2. Scheme of the digital protocol Thanks to CINECA experience in the field of OpenSource we are trying now to orient new research activities (applied to landscape and archaeology) towards: the use of a complete OpenSource approach in the steps 2 and 3, replacing where it’s possible, traditional tools with open software, and creating a new sector of applications open and web-based. In this way we think that the introduction of the concept of OpenSource in the field of Cultural Heritage will be real challenge for its future developments, based on its economic impact, sustainability, flexibility, adaptability and on its strong push towards interdisciplinary and multidisciplinary work, towards data, technologies and methodologies exchanges. A new digital protocol is being signed by the two interdisciplinary teams on this topic.
Figure 1. GIS and Virtual Reality connection. In the last years we have obtained some reasonable results in the field of ancient landscape reconstruction through digital technologies (Forte, Williams, 2001; Forte, 2003). This allowed us to define a digital protocol (Fig.2) in which is schematically exemplified the methodology we use to study, reconstruct and generate 3D dimensional landscapes, accessible in real time in a Virtual Reality environment on a Desktop PC (Forte et alii, 2004). The use of Terrain Generator has been surely a turning point in the integration of different typologies of data available, inside a
OpenSource: a challenge for Cultural Heritage New research activities have been activated since 2004 and they have been focused on OpenSceneGraph library for paged terrain generation, through an OSG tool called OSGdem, and on Virtual Terrain Project (another open project based on OpenSceneGraph). Two dissertations have been assigned on this topic and a workshop (“OpenSource and Archaeology”) has been organised with surprising results. This workshop, held in occasion of the international conference CAA2004 – Computer Application in Archaeology (organised by Calori, Hermon,
Niccolucci, Pescarin), stress the importance of the argument and encouraged CNR ITABC to open a new parallel research activities on OpenSource and Cultural Heritage, based even on a cooperation with CINECA Visit Lab, offering testing cases and reporting this experience through material, tutorials, documentations to be published. We have chosen to orient our framework on the platform OpenSceneGraph for many reasons. First of all for its portability. As will be discussed in charter 2.2, OSG is available for Linux, Window and SGI. It’s possible to find examples of applications with different GUI and even with ActiveX modules. Its compatibility with modelling standards is also very important: OpenSceneGraph manages in fact .flt and .3ds models, paged terrains produced with other software such as Terrex Terravista (flt, txp). Moreover there are also available exporters for 3ds Max, Maya and Blender. Even its performance can be considered a good quality of this library, allowing advanced rendering techniques, such as vertex and fragment shaders, MultiTexturing, shadows, impostors, etc. Pagingnetworking possibilities make OpenSceneGraph open to use paging techniques for terrain generation (as TerraPage formats).
. maintain the same modelling formats of 3d objects reconstructed with photo-modelling or scanner-laser techniques and processed with external software, such as 3DStudio Max (3ds, flt, osg, ive) . create libraries of 3d models and vegetation typical of the area and of the period . connect directly inside the three-dimensional geographical space the models (fig.3) and the vectorial themes (shp files) (with VT Builder and VTP Enviro). . working dynamically at the reconstruction of the visible archaeological landscape, testing hypothetical thesis, preparing the data for a complex VR application, based on story-telling approach (based on VirTools: www.virtools.com). . and finally publish the results of the surveys over the Web, updating them at each new campaigns through an ActiveX component realised by CINECA Visit Lab team (fig.5).
OPENHERITAGE VR SYSTEMS Real Time 3D landscape reconstruction: the case of Appia Archaeological Park and Certosa Museum project In two cases we have experimented the new protocol: the “Appia Antica project” and the “Certosa project”. We have chosen these two case-studies even because they have different aims; in this way we could test how our methodology could be applied in the two main activities connected with Cultural Heritage: research-mapping-management-conservation and dissemination-didactic-musealisation. In the case of the Appia project, in 2002 CNR-ITABC signed a research agreement, together with the Municipal Superintendence of Rome, that regarded the realisation of mapping activities inside the archaeological park and the realisation of a bi-dimensional and three-dimensional database of the monuments of the Appia Park in Rome. Two CNR-ITABC research teams are working (the project will end in 2006), at the project with different purposes: topographic survey, architectonic aspects of the monuments with stereophotogrammetric techniques (Salonia et alii, 2003) and virtual reconstruction of the archaeological landscape, starting from data acquired directly on the field. Part of the effort was dedicated to the creation of a VR system that could be a research and co-operative working tool, during the phases of the project, and a complex VR application in a future documentation and museum centre that could be realised inside the park. The use of OpenSource tools changed the approach even to VR, leading to the creation of personalised spatial tool useful to: . link/connect all the data that were acquired during the survey campaigns in the Appia park . keep the same geographical projection used in the realisation of the GIS . maintain the same GIS formats of data (DEM in ascii grid format, vectorial shape files, geotiff and geojpg) . generate quality paged and tiled terrains of the area from GIS data (with OSGdem)
Figure 3. The Appia park during the reconstruction phase inside VTP Enviro (modified version) The “Certosa project” is a project of Bologna City Council (New Institutions for Communicating the City) and CINECA. It is currently developing a virtual museum for the city, a complex VR application regarding several cultural that will constitute the basis of a Museum for Accessing the City of Bologna. The fundamental idea is the visual mediation. An interactive visual portal is the access to historical and cultural contents. Choices are guided by vision and the virtual environment presents information in a user friendly manner. The actual territory that the application can visualize is the second most important concept around which the application revolves. This aspect enables a user to put into relation different historical events and topics, gathered under the same context that unifies dispersed cultural resources. For the development of this application three different sites (two in Bologna and one in its surroundings) have been selected as a starting point for the process of valorization: the Certosa monumental cemetery, that include several significant monuments and even an archaeological Bronze Age site: an Etruscan necropolis; the Memorial Wall, a monument raised in remembrance of the Bolognese people killed in the fight for liberation during the Second World War; and the area of Monte Sole park, sadly known for the mass executions of civilians carried out during the Second World War (LIGUORI et alii 2004). The VR application was developed inside the VISMAN framework, based on SGI Performer. During the development of the Etruscan part of the application, there was the necessity of starting a co-operative reconstruction project for the Bronze Age landscape, together with the
archaeological museum experts. This led us to approach the problem carefully and in a updateable, open and scientific way, before getting to the VR application whose primary goal was the dissemination and musealisation of the Certosa history. Such in the case of Appia Antica project, OpenSource tools allow to follow this approach. A GIS base was constructed, a database was realised and connected with the georeferenced object. A first attempt of Etruscan DEM and GeoImage was realised. The 3D terrain was generated with Terrex Terravista because we needed FLT flight files in the following phase (Visman). GIS vectorial layers and the terrain were imported in a modified version of VTP Enviro (Camporesi, 2005), that was used as 3D environment to reconstruct dynamically the archaeological landscape (fig.4 right). With Enviro it was possible: to connect 3d models of the steles and other archaeological objects in the position where archaeologists found them during 18th century excavations; create library of plants known to be typical of that area during the Bronze Age and add in real time the vegetation; control parameters and hypothesis in 3D. Although the project is at beginning we have found that the approach used created a collaborative connection between different institutions and disciplinary teams, opening positive discussions aimed at landscape reconstruction, while at the bottom a scientific digital basis is prepared (GIS, DB) and continuously updated.
Figure 4. Construction of the GIS, reconstruction phase of the landscape inside VTP Enviro OpenSource components As we describe above, as real time scenegraph library we use OpenSceneGraph (OSG, www.openscenegraph.org). This library, based on OpenGL, offers the following features: Crossplattform (Windows, Linux, Irix) Real Time optimisation Wide range of input format support (flt, 3ds, obj, osg, ive) Extensible through-plug-in architecture Built in support of paged lod terrain generation and navigation OSG already provides both a tool to generate hierarchical paged terrains from Geoimages and Digital Elevation Models and a network loader capable of providing browsing of such hierarchies with reasonable bandwidth requirements. The generation tool (OSGdem) has been used to build a base paged virtual terrain models of our test-cases. OSGdem produces the hierarchy of terrain patches as a directory of .ive native optimized and compressed .osg format files. By exposing this directory to the Web (we have used a simple Apache Web Server) it’s possible to use the example viewer tool
(OSGviewer) to browse the terrain by opening the topmost archive file. The built-in paged LOD engine of OSG takes care of loading the required terrain patches, according to the user selected view position and orientation; the framerate is kept as constant as possible, while the background thread keeps increasing the detail of the loaded tile-patches. OSGviewer is available on both Windows and Linux. Even if OSGdem can produce good quality paged terrains, it does not handle any culture data or 3d models. On the contrary, as explained, we use VTP Enviro in order to interactively modify the landscape, adding and modifying culture data and 3d models, taking them from 3d libraries. Enviro and VTBuilder are tools developed within the Virtual Terrain Project software framework (www.vterrain.org). VTBuilder allows processing of GIS culture data (such as tree coverage, river and road centrelines, lakes, etc), Digital Elevation Models and Geoimages and produces a 3D landscape database (stored as XML file format). Enviro is an interactive browser and editor of such database. Both tools are cross platform and released under OpenSource licence. Unfortunately the VT terrain database is not well suited for large terrains network walk through, because it does not provide paged terrain structure. Thus, in order to support our virtual reconstruction project, we decided to integrate OSGdem and VTP Enviro. Enviro already uses OSG as rendering library, so the integration work has been reasonable. Within the effort of a thesis dissertation, Enviro has been extended as to allow osg/ive terrains import, in this way the native Enviro base DEM (bt format) can be substituted with a more efficient OSGdem hierarchy. The Enviro user can now access all the Enviro interactive editing functionalities with a OSG terrain. At the end of the interactive section, the user can save the culture data within the existent OSGdem paged terrain structure. The result is a paged terrain with culture 3d data on it (trees, streets, buildings, sites, labels, etc.). Exported data, structured in this way, can be browsed with OSGviewer, as we have mentioned before. In order to improve Web presentation, all the necessary OSG components have been assembled into an ActiveX Internet Explorer plug-in. At present the status of this part of the framework is still under development at CINECA Supercomputer Centre. CONCLUSION 1.1 A sight into the future Since last releases of OpenSceneGraph it’s quite clear the direction and potentialities of this library for the publication of large and complex territories over the Web. The work we have done until now is simplifying the production of 3D landscape useful for real-time navigation of any user, even from home, without having to download locally huge amount of data. After these experiences we planned further developments. The goal we would like to reach is the creation of a 3d shared and interactive working system, web based. We are planning to combine different Open Source technologies, based mainly on OSG library, and to obtain an
environment whose modelling and reconstructing aspects are accessible and adjustable through the Web. Some experimental tests has already been done in this direction. The complete system we are planning to create is formed by: − A GIS repository based on an OpenSource WebGIS − A 3D Models repository based on OSG, PhP and PostgreSQL − A plug-in viewer for Internet Explorer for .ive (and .txp) formats, and either a stand alone application fot other browsers. − An editing client with the same functions of the viewer and some added functions which allow a user to set preferred points of view or paths or to modify some aspects of the landscape, adding new buildings or trees in geographical position, taking them from the repositories. − A server component to which is demanded the ….. of distribution of data recalled by the viewer client and to accept and validate the insertion and variation requests produced by the editing client − A rebuilding tool (batch) that, since the beginning, periodically and on demand, activates a terrain regeneration procedure in order to apply the modified elements. Some adjustments would need a longer regeneration time (as in the case of modification of the DEM or of an aerial image that would request a complete re-computation of the entire terrain model), compared to other (such in the case of added trees or models at a certain point).
Bateson G., 1979, Mind and Nature. A Necessary Unit, Dutton, New York. Camporesi C., Generazione di paesaggi tridimensionali. Un approccio OpenSource per applicazioni real-time e web-based, dissertation of univ. of Bologna, Dept. of Computer Science (Prof. G. Casciola) Calori L., Guidazzoli A., Forte M., 3D Virtual scientific visualization of archaeological sites: new navigation metaphores, in Scienza e Supercalcolo, CINECA luglio 1996, Bologna, pp.9-12. Calori L., Diamanti T., Guidazzoli A., Liguori M.C., Mauri M.A., and Valentini L. (2003), Certosa virtual museum: a dynamic multilevel desktop VR application, poster in Eurographics 2003 Proceedings, 1-6 September 2003, Granada, Spain. Calori L., Diamanti T., Felicori M., Guidazzoli A., Liguori M.C., Mauri M.A., Pescarin S. and Valentini L. (2004), Databases and Virtual Environments: a Good Match for Communicating Complex Cultural Sites, in Proceedings of ACM-SIGGRAPH 2004. Forte M. 1996 (a cura di), Archeologia. Percorsi virtuali delle civiltà scomparse, Milano, 1996. Forte M. 1997 (ed.), Virtual Archaeology, Harry Abrams Inc. Publishers, 1997. Forte M., Williams P.R. (eds.), The reconstruction of Archaeological Landscapes through Digital Technologies, Proceedings of the 1st Italy-United States Workshop, Boston, Massachusetts, USA, November 1-3, 2001, BAR International Series 1151, Oxford, 2002 Forte M. (eds.), The reconstruction of Archaeological Landscapes through Digital Technologies, Proceedings of the 2st Italy-United States Workshop, Rome, Italy, November 3-4, 2003, BAR International Series, Oxford, in print Forte et alii 2003: Forte M., Gòmez L., Pescarin S., Pietroni E., Vico L., Integrating Technologies: The Appia Antica Project, Proceedings of the 2st Italy-United States Workshop, Rome, Italy, November 3-4, 2003, BAR International Series, Oxford, in print
Fig.5 Access and Editing Tool
REFERENCES Bateson G., 1972 Steps to an Ecology of Mind , San Francisco, Chandler Press. Barcelo J., Forte M., Sanders D., 2000 (eds.), Virtual reality in archaeology, Oxford, ArcheoPress (BAR International Series S 843), pp. 247-263.
Forte et alii 2004: Forte M., Pescarin S., Pietroni E., Dell’Unto N., An integrated approach to archaeology: from the fieldwork to virtual reality systems, in Proceedings of CAA2004, Prato Apr.04, in print Guidazzoli A., Forte M., Archeologia computazionale tra Visualizzazione Scientifica, computer vision e realtà virtuale, in Atti della Seconda Giornata Internazionale sulle applicazioni della realtà virtuale e delle tecnologie avanzate all'edilizia e all'architettura, Bologna, 1995, pp.14-23 Levy P., 1997, Il virtuale, Raffele Cortina Editore, Milano, 1997 Liguori M.C., Pescarin S., Diamanti T., Guidazzoli A., Felicori M., 3D Temporal Landscape: a new medium to access and communicate archaeological and historical contents, in Proceedings of CAA2004, Prato Apr.04
Maturana, H., F. Varela, The Tree of Knowledge: the Biological Roots of Human Understanding, Boston: Shambhala, 1987, (Revised Edition: same publisher, 1992). Pecchinenda G., 2003, Videogiochi e cultura della simulazione, Editori Laterza, Roma-Bari Salonia, Negri, Valdarnini, Scolastico, Bellocci, Innovative quick photogrammetric systems for 3D Cultural Heritage documentation: the Appia Antica project , in Proceedings of the 2st Italy-United States Workshop, Rome, Italy, November 3-4, 2003, BAR International Series, Oxford, in print OpenSceneGraph web site: http://www.openscenegraph.org Virtual Terrain Project website: http://www.vterrain.org ACKNOWLEDGEMENTS Partner of the Appia Antica Project: CNR-ITABC, Istituto per le Tecnologie Applicate ai Beni Culturali (Maurizio Forte, Paolo Salonia coordinators); Archaeological Superintendence of Roma municipality (coord. Paolo Grassi, Antonio Mucci, Luca Sasso D'Elia); Italian Archaeological Superintendence (Dott.sa Paris); CINECA Visit Lab: Cooperation on OpenSource tools for the reconstruction and visualisation of archaeological landscape. Partners of the Certosa Project: Bologna municipality (M. Felicori, C. Borgatti, M.C. Liguori, R. Martorelli, M.Bacchini, N.S. Onofri, M. Lodi); CINECA (A. Guidazzoli, A. Mauri, F. Delliponti, L. Calori, T. Diamanti); CNR ITABC (S. Pescarin); HERA (M.Gaeta, R. Zanetti); Istituto Parri: (L . Alessandrini, L. Cigognetti, C. Crupi); Archaeological Museum (C. Morigi Govi, M. Marchesi) A particular thank to Silvano Imboden (CINECA), Carlo Camporesi (UNIV. of Bologna) and Marcello Morgotti (CINECA).
