Open Heritage: an Open Source approach to 3d real-time and web ...

Open Heritage: an Open Source approach to 3d real-time and web-based landscape reconstruction Sofia PESCARIN**, Maurizio FORTE**, Luigi CALORI*, Carlo CAMPORESI***, Antontella GUIDAZZOLI*, Silvano IMBODEN* * CINECA Visit Lab, via Magnanelli 6, Casalecchio di Reno (BO), Italy. Mail: [l.calori],[s.imboden],[a.guidazzoli]@cineca.it ** CNR ITABC VHLab, via Salaria km 29,300 – 00016 Monterotondo St. (Rome), Italy. Mail: [sofia.pescarin],[maurizio.forte]@itabc.cnr.it; web: www.itabc.cnr.it/VHLab *** University of Bologna, Dept. Computer Science, Bologna, Italy Abstract. The paper will discuss the problematic approach of ancient landscape reconstruction, stressing the importance of data and information sharing through the web. Thanks to new possibilities offered by Open Source approach and, in specific, by some tools, such as Virtual Terrain and OpenSceneGraaph, it’s now possible to construct a web-based shared system, allowing users and experts to interact dynamically with complex landscapes and large territories, in 3d and in real time. Might this methodology, presented through some case-studies, open to a real participation of world-wide communities to Public Administration policies? Might it push towards collaboration and dissemination in the field of Virtual Heritage?

1. Introduction and State of the art The role of the Internet for the knowledge and sharing of multidimensional information is fundamental. GIS is today one of the most used tool in many fields related to the territory management and its study. Even in the field of Cultural Heritage, digital mapping and geographical data management through a Geographical Information System is almost recognised as important for conservation, protection, analysis and communication issues. WebGIS is the perfect way to share even geographical information, allowing the user to view raster and vector information in overlay, to load and unload, query, compare, upload and download data in a simple way, through a browser. Many commercial software are available for this purpose, offering server-client solutions at different levels of complexity/price/completeness. But there are today also other possibilities offered by the Free and Open Software movement. Open Source projects, such as MapServer, have developed interesting solutions for WebGIS. [23] “Time-component”, that is strictly connected to archaeological and historical data, has also been studied in connection with “Spatial-component” and some good projects and tools have been developed for the Web. For instance ECAI experience (Electronic Cultural Atlas Initiative) was surely positive, in particularly with TimeMap that today offers the possibility to “provide an engaging and intuitive method of delivering historical, community, government, research and business information. Combining mapping and the time dimension gives new ways of visualising urban growth, the spread of empires, heritage sites, environmental change, weather patterns, traffic flow, earthquakes, mobile network faults, and much more.” [24] [25] The term “WebGIS” was often used, commonly, for systems that could manage and visualise

in two dimensions, through the Web, both bi-dimensional and three-dimensional geographical data. Recently a newer interest seems to be turned to a more complete and complex approach: toward the visualisation of fully three-dimensional geographical data inside 3d environments. The words 3D GIS and 3D WebGIS is becoming quite common. In the cultural field, archaeology above all, Desktop Virtual Reality applications represented a fundamental experience, still in progress [1][5], and also an example to create stand-alone solutions (for museum installation for instance), but also for on-line applications. In this last case we tried to analyse what was available and published over the web as projects and applications. We tried to compare and use as reference, two of the most used and success experiences, even for the diversity of their methodological approach, technology used and cost: VRML and Skyline Software System1 [22]. Both these solutions revealed some values and some defects that gave us the suggestion to try an alternative solution: a completely OpenSource approach to construct a system to publish on-line 3D interactive landscapes, through a real time fly through. 2. On-Line ancient landscape interactive reconstruction 3D visualisation of bi-dimensional and three-dimensional data offers a concrete possibility to adjust spatial information to models complexity. Today, indeed, data acquisition activity, thanks to highly precise tools such as DGPS, Laser Scanner, remote sensing technologies, is more and more incrementing their quantity, quality and resolution. Even for this reason it’s almost impossible to keep on using traditional systems to communicate and manage this kind of data. The creation of a protocol becomes a priority, useful also to suggest a direction and to convert all the data open and shared formats. With a digital protocol it’s then possible to overlay and compare different data, coming from different realms, from different sources, at different levels of detail, with different formats and projections. In the case of CNR ITABC teams, this was a real necessity, since we are usually dealing with all the phases in the study of archaeological landscapes: from the mapping on the field, through data post-processing, to the reconstruction of landscape (at micro and macro scale) and to the construction of Virtual Reality Applications. [6] We believe that in the next future data sharing will be central in the field of cultural heritage. Therefore we should try to think more of open-formats than of standard-formats. What we needed at first was the definition of such a protocol, a “spatial pipeline”, a method that could allow to: - maintain the same kind of method, used for the realisation of Virtual Reality applications [6] - maintain the same kind of data and formats acquired and processed - integrate data and technologies already known - maintain spatial and geographical information of data - use as input files the same of the GIS (geoimages, culture vector data, DEMs) - use graphic libraries of objects, models, etc.. - push towards a co-operative approach for interdisciplinary teams - simplify data and information sharing - communicate easily to an end-user how is and how was an archaeological landscape - allow limited expenses focused more on “human” investments then on “technology”

1

Although there are other examples that we have analysed or are planning to compare such as: landscape navigation based on the use of Macromedia Shockwave: (i.e: fly on Tuscany regio: http://www.rete.toscana.it/sett/pta/cartografia_sit/sit/elba3d/it/start.htm) or based on DirectX

Thanks to the interdisciplinary work of different professionals (archaeologists, computer scientists, GIS experts) and the combined used of open tools (OpenSceneGraph, VTerrain, MapServer, PostgreSQL and PostGIS) and etherogeneous data at different levels of detail (historical, architectonic, topographic, etc), it was possible to go beyond a WebGIS, defining a VR-Landscape Web System (Table 1), that we can even call 3D-WebGIS. The system integrates different technologies and tools so to obtain: 1. terrain generation from GIS data (geoimages, vector files such as shape files, culture data such as vegetation, roads, monuments, etc.) 2. management of different graphic libraries created on purpose for different projects 3. dynamic and interactive modification of the landscape: adding 3d models. Vegetation, vector layers, labels and so on 4. export features of the final landscape obtain in the reconstruction phase (step 3) in a file format useful for the Web 5. landscape visualisation in three dimension inside a web browser 6. landscape data interaction (upload, download of different thematic layers) (fig2) Step

Input

Tool

Functionality / Modified Tools and Output Code

1. Terrain Generation.tiff, .jpg GDAL lib. .dem, .ascii, .grid, ecc.OSG (OSGdem)

Generation of tiled and paged terrain from *.osg, *ive geoimages and dem (even at different LOD) / no modification 2. Graphic Libraries.3ds, .ive, .osg, .obj, Different modelling Creation of libraries of objects, plants etc. with *.osg, *ive creation.flt (3d models); .png, software (Blender, different software (low resolution models at different .rgb, .jpg (plants) 3dStudio Max, Multigen LOD); eventually translation in .osg or .ive file Creator…) – XML (for format / conversion tool for openflight hyerarchical plants) - OSG files: flt2ive (OSGconv) 3. Landscape.shp, .3ds, .ive, .osg, VTBuilder - VTEnviro Modification of the landscape, using as base the *.bt, *.jpg, *.vf Reconstruction .obj, .flt OSG terrain created in step 1: add new models, (plants), *.vtst add plants and other culture, add labels, add vector (structures), *.rmf (roads) layers, modify existing / modified version of VTBuilder and VT Enviro, enabled import capabilities for OSG/IVE/FLT/TXT terrains 4. Landscape Export*.bt, *.jpg, *.vf (plants), VTEnviro Export of models, plants, culture, vectorial layers, *.osg, *ive *.vtst (structures), labels as separate files or as paged integrated in *.rmf (roads) the different tiles that represent the landscape / enabled export capabilities to *.osg and *.ive formats 5. Landscape*ive OSG (network loader) - Use of OSG network loader for Internet terrain data Visualisation over the ActiveX publishing inside an ActiveX / ActiveX Web 6. Landscape *ive, *.tcl, *.html Apache Server, Php, Creation of database for models, based on spatial *.html Interaction PostgreSQL, PostGIS information, at Server side; possibility to interact dynamically with the terrain through the DB: adding new point of views, adding new models, switching between models… / Php program Table1. VR Landscape Web System

3. Technical issues: OpenSource components As real time scenegraph library we used OpenSceneGraph [15]. This library, based on OpenGL, has many features such as: crossplattform (Windows, Linux, Irix), real Time optimisation, wide range of input formats support, 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 (table 1). The generation tool (OSGdem) has been used to build a base paged virtual terrain models of our test-cases: Appia Antica archaeological park (Rome, Italy) and Bologna territory (Italy). OSGdem produces a hierarchy of terrain patches as a directory of .ive native optimised and compressed .osg format files. Exposing this directory to the Web (we are using a simple Apache Web Server) it’s possible to use the example viewer tool (OSGviewer, available both for Windows and for Linux) 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 frame rate is kept as constant as possible, while the background thread keeps increasing the detail of the loaded tile-patches. Even if OSGdem can produce good quality paged terrains, it does not handle any culture data, vector information in GIS format (shape files) or 3d models. For this reason we decided to integrate another open source project: the Virtual Terrain Project [16]. This project has already produced two really useful tools that we studied and used since the beginning, modifying their code: VTBuilder and VTP ENVIRO. Both tools are cross platform and released under OpenSource licence. Moreover Enviro is based on OSG library. With VTBuilder it is possible to manage GIS culture data (such as tree coverage, river and road centrelines, lakes, etc), Digital Elevation Models and Geoimages and to produce a 3D landscape database. VTBuilder imports GIS commonly used data, so it is quite easy to adopt it. It prepares data in xml or binary file formats that are then stored in the landscape database (as XML file). VTP Enviro was then used in order to interactively modify the landscape, adding and modifying culture data and 3d models, taking them from 3d libraries. Enviro is a viewer and an interactive browser and editor of such XML landscape database. Unfortunately the VT terrain database is not well suited for large terrains network walk through, because it does not provide paged terrain structure. (fig.1) Thus, in order to support our virtual reconstruction projects, we decided to integrate OSGdem and VTP Enviro. Enviro, as we have seen, already uses OSG as rendering library, so the integration work was reasonable. Thanks to a thesis dissertation [2], Enviro has been modified and extended in order to allow osg/ive/flt(openflight)/txp(terrapage) terrains import. In this way the native Enviro DEM (bt format) could be substituted, with a more efficient OSGdem hierarchy. 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.) (fig.1). Exported data, structured in this way, could be browsed directly with OSGviewer. 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. 4. Case-studies The framework has been already tested in two case-studies. In the first project (the Certosa Virtual Museum), the environment provided by VT ENVIRO allowed an interactive reconstruction of the Etruscan landscape of the Certosa

(the Etruscan Necropolis, today monumental cemetery of the city of Bologna, Italy) [3], [4]. The reconstruction phase was possible thanks to a collaborative approach with the Archaeological Museum of the city and based on scientific GIS project. Data were prepared in a GIS (ESRI ArcView), connected to Databases, validated by the museum and then used to generate the actual landscape (fig.1 a-c) and an example of Etruscan landscape. The project is still in progress and its future development will probably regard the realisation of VR installation on the entire landscape of the Etruscan city of Bologna.

Fig.1 a,b,c,d. The Certosa Virtual Museum project. Actual landscape in VT Enviro (a,b ), Export phase of Etruscan thematic layers in .osg file format (c ) and the Etruscan landscape connected to GIS data (d )

In the case of the Appia Antica Project, the system was used to publish on line archaeological data and to create a base for a shared interactive system useful even for the team during the phase of work [5] [6]. This project in fact regards the creation of a 3D spatial archive of the monuments of a wide archaeological park in Rome (the Appia Antica Archeological Park), through intense mapping, GIS and modelling activities. This project is founded by the Municipality of Rome and it last four years (2003-2007). After this period, the spatial archive could be opened to public access (for scholars and for tourists) through a DVR installation. In the meanwhile a Web Site [21] has been realised with different goals: first of all to connect the teams that are working on the project (2 teams of CNR ITABC and 1 team of Municipal Archaeological Superintendence), allowing data sharing (data section), survey activities planning (data and webGIS section), visualisation of partial mapping results (webGIS section), visualisation of the three-dimensional reconstructed landscape and of the modelled monuments (3D section). In the 3D section a user can visit the Appia Archaeological Park (as appears from an Ikons

Satellite view), moving inside its archaeological landscape, observing the vegetation and the monuments, switching to a cartographic view of the same area. The three-dimensional and interactive landscape represents the area of the archaeological Park of the Roman Via Appia as it appears today (observed landscape). Since the project is still in progress, new tools will be added as soon as they are developed by the programmers of CINECA team. The Web itself is used as research window.

Fig.2 a,b,c,d. Appia Antica Project. The web site and different active functions: navigate inside the landscape, upload 3d models, switch to cartographic view, upload vector layer (park area)

While CNR ITABC team was responsible for the data acquisition on the field, cartographic data elaboration inside a GIS and 3d archaeological monuments modelling, CINECA Visit Labs dedicated its efforts to the realisation of the ActiveX and to the development of export and publication functions for the vegetation and 3d models inside the landscape. The requirements to access the 3D Section are: broadband connection (ADSL), OpenGL Graphic Card and ActiveX installed. 5. Conclusion and Future developments Open source WebGIS represents the future of what we define cultural spatial pipeline, from the fieldwork to an on-line virtual communication; a bridge between virtual reality systems and GIS archives. In the close future one can expect a growing integration of 3D graphic models and libraries in GIS domains, so the development of 3D WebGis projects will be

relevant. In addition, the faculty to create on line VR cultural landscapes in interactive way (constructing the landscape by 3D graphic libraries), constitutes a new spatial and user friendly tool for users interested to the reconstruction of the environment and for correlating possible virtual scenarios in real time. WebGIS is very important, since it allows a complete control and interaction with data. For this reason we are testing MapServer open source WebGIS, even to analyse the possibility to integrate it with OSG, connecting a 2d view with the 3d view. The investment in Open source software, in particular for non profit, public administrations and research centres, will permit to give public access to a wide community of users to spatial cultural data. For this reason we are testing MapServer OpenSource WebGIS, even to analyse the possibility to integrate it with OSG, connecting a 2d view with the 3d view. This direction of research is still in progress, but we expect to create: a GIS repository based on an OpenSource WebGIS; a 3D Models repository based on OSG, PhP and PostgreSQL; a plug-in viewer not only for Internet Explorer but also for other browsers; a more complete editing client with some added functions such as adding new buildings or trees in geographical position, taking them from the repositories; a server component to which is demanded the task of data distribution recalled by the viewer client and to accept and validate the insertion and variation requests; a rebuilding tool that periodically and/or on demand, activates a terrain re-generation procedure in order to apply the modified elements. Since 3D is a perfect communication factor, pushing, at the same time, development and comparison, a VR Web System could surely help Distance Learning, for instance, or Virtual Communities. Even in the case of Urban Planning it could be a concrete tool to promote citizens participation to cultural and planning politics of Public Administrations.

Aknowledgments We would like to thank the partner of the Appia Antica Project: CNR-ITABC teams coordinated by Maurizio Forte and Paolo Salonia; Archaeological Superintendence of Roma municipality (coord. Paolo Grassi, Antonio Mucci, Luca Sasso D'Elia); Italian Archaeological Superintendence (Dott.sa Paris); CINECA Visit Lab for the Cooperation on OpenSource tools. We would like to thank all the partner of the Certosa project: Bologna municipality (M. Felicori, C. Borgatti, M.C. Liguori); CINECA (A. Guidazzoli, F. Delliponti, L. Calori, T. Diamanti, S. Imboden, C. Camporesi); and the archaeological museum for the data and the active collaboration to the project (Dir. Cristiana MorigiGovi and Dr. Marinella Marchesi). References [1] Barcelo J., Forte M., Sanders D., 2000 (eds.), Virtual reality in archaeology, Oxford, ArcheoPress (BAR International Series S 843), pp. 247-263. [2] 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) [3] 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. [4] 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. [5]

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