Proceedings of “From Space to Place”
Sharing interpretation: the challenge of Open Source web approach Luigi Calori1, Carlo Camporesi2 , Augusto Palombini2 , Sofia Pescarin 2 1
2
CINECA Visit Lab, Bologna, Italy ,
[email protected] CNR ITABC, VHLab, Rome, Italy, [carlo.camporesi].[augusto.palombini],[sofia.pescarin]@itabc.cnr.it
1 Introduction
2 VR WebGIS Project of CNR
The impact of digital technologies is going to cause a drastic change both in the working process and in theoretical and epistemological settings of archaeological science and cultural heritage management, forcing everybody to rethink the traditional ways of information validation and diffusion. Today, digital technologies let a large amount of information to be available and transmittable in short time. Almost everybody can potentially create and diffuse data to the whole world population, or at least to that who can reach the web, setting up relevant problems in terms of scientific validation. Science, in this sense, seems to have to change its tools: from a narrow scientific community who controlled the access to publication, to an open approach in which everybody can be an actor, and information reliability relies on the transparency of its sources and of the development process (e.g. Camporesi et al. 2006, Feller and Fitzgerald 2002; Forte, 2005). According to this approach, an open process can not only be focussed on the adoption of Open Source software, but it implies also the application of an open approach in the use of interpretation and validation structure. A famous example that explains the aspects of Open Source is the one described by Eric Raymond in his famous book “the cathedral and the bazaar”, where he describes Commercial and Open software development philosophies as Cathedral and Bazaar models (Raymond 1999). In the Cathedral model, software projects are developed by small groups of experts, while in the Bazaar model everybody can look at the people working, participate, give suggestions and critics. It is interesting to think that this metaphor could be also applied to a general scientific interpretation process, distinguishing a traditional Cathedral way from a different Bazaar process, open to public or at least to a wider evaluation by the transparency of its creation process. In this latter approach, the open dimension of information and the use of open source software are two elements of the same process, that recall each other.
In accordance with these considerations, we started a new research direction in our lab, the Virtual Heritage Lab (VHLab) of the National Council of Researches, Institute of Technologies Applied to Cultural Heritage (CNR ITABC), testing the the potentiality of such tools. We were aimed to face some problems related to the broad diffusion of archaeological scientific data through the web, as well as to consider the state-of-the art of open source software in our field and its suitability for a large community of non-programmers, as that represented by archaeologists, historians, art historians, etc. We tried to use open source software in our projects, trying to analyse the possibility to convert or extend commercial tools already part of our digital pipeline into open ones. Moreover we tried to develop new open tools, building a bridge with IT experts and IT institutions, such as the Visualisation Lab of Cineca Supercomputing Center, signing a research agreement. Finally we tried to apply to our projects and to our applications (based both on open and commercial tools) an open and transparent approach, focused on metadata publications, on interaction and on information communication. Our effort was focussed on the realization of a VR WebGIS based on the 3D open engine OpenSceneGraph (www.openscenegraph.org), on a modified version of the Virtual Terrain library (www.vterrain.org) and on a visualization Plugin, the OSGvisWeb completely developed by the team, for Mozilla Firefox and for MS Internet Explorer, for 3d web data interactive fruition. The software development was planned by CNR (mainly 2d webGIS and plug-in for Mozilla) and CINECA (terrain generation and plug-in for Explorer). The main feature of this tool is the opportunity to create and browse in real time virtual reality environments and terrains. In order to achieve an open approach also in term of transparency policy, we have also developed specific features for data exchange and verification in the VR webGIS environment. These tools and features were partially developed and applied for the first time in the Appia Antica project (Forte et al., 2005). Others were better defined and newly developed in the case of the Flaminia project, in which the open approach become a sort of guideline during its development.
In the first case study, the Appia Antica Project (fig. 1), the primary goal was the realization of a spatial 2d and 3d archive for Roman Superintendency of a wide archaeological park, in the southern part of Rome1. Data were collected directly on the field in topographic (DGPS, PDA, Laser Total Station) and architectonic survey (Total Station, Laser Scanner, digital camera, etc.). Terrain information were acquired and processed in a GIS and published in a webGIS; we used the open source MapServer for this purpose, working on the interface with the tool Chamaleon. 3D terrain and models where then published in a separate VR webGIS section, together with vector information, thematic layers, vegetation attributes and alternative switchable 3d terrain models.
Fig.2. Screenshot of the OSGVisWeb interface (on Mozilla Firefox) and the Flaminia Project.
3 Open source and virtual archaeology
Fig.1 The Appia Antica project, on the left: From GIS project to web 3d navigation and interaction; 3d dynamic off-line environment for landscape reconstruction and 3d data published over the web.
In the second case study, the Flaminia Project, we worked on a website with the aim of creating, since the very beginning, a real working tool for the team and all other partners (Fig.2). In the web project we tested different solutions for interpretation and communication. Data transparency was also considered a fundamental goal, achieved through the publication of metadata connected to switchable models.
1
The project was developed by CNR ITABC, under the direction of M. Forte and P. Salonia for Roman Superintendence, with the cooperation of technical sponsors and the research contrinbution of CINECA (www.cineca.it). See Forte, Pescarin, Pietroni, 2005, pp. 79-95
The use of Open Source software is certainly the first goal in our approach. As a matter of fact, the empiric premise of any validation process is based on the reproducibility of the data production chain. Then, whoever presents a set of data through the web should give a sufficient information both on original sources and on the software used, to allow everybody to check the products. Only dealing with open source software we can really define such a process as open to everybody's checks. This step is still conditioned by a general problem. Why Open Source, despite of its well-known advantages in terms of cost and availability, is still far from a general diffusion? Without a deep analysis of such a complex and studied topic (e.g. Bonaccorsia and Rossia 2005, Economides and Evangelos 2005), we can see that in most of people vision, Open Source suitability problems are related to some specific items, such as: lack of information on products and features, difficulties in installation and use, lack of user-friendly interface and – above all – the need of a gradual shift from their traditional commercial software to the open packages, so that the path to a diffused use seems to pass through: 1- The adoption of an open source working chain 2- A complete portability Windows/Linux of the process and a search for applications available on both the operating systems. 3- The selection of user friendly open source software. 4- A particular effort to move technical problems from the user side to the server side, through the creation of pre-compiled software packages.
Proceedings of “From Space to Place”
An overview of the available applications for the production of GIS layers, DTMs, and 3D models reveals that many of these problems are today overcome. Figure 3 shows that the first three steps of the list above are substantially overcome.
to archaeologists (ArcheOS “Akhenaton” www.arcteam.com) (Bezzi et al., in press). It is a Debian-based Linux distribution containing all the software needed for the 3DWebGis working chain. The situation is currently more complex on Windows platforms, but the realization of a complete suite containing self-extracting software binaries, tutorials and links, to let the end-user to avoid all installation problems, is one of our next goals. The current step has been devoted to the realization of a VR WebGIS totally based on open source software, absolutely easy and friendly for the end user, shown in fig. 1 and 2.
4. OSGVisWeb: Visualization infrastructure for Mozilla and Explorer OSGVisWeb is a platform created to view and manipulate 3D terrain models through web pages. It's completely written in C/C++ language and based on the middleware OpenSceneGraph (a real-time OpenGL rendering library). OSGVisWeb is easily adaptable to HTML pages (published through MS Internet Explorer and Mozilla Firefox browsers), and easy to control by JavaScript instructions. It doesn't need dedicated services on the Server side.
Fig.3. Table of open and commercial software available on different operating systems.
As shown in fig. 3, the whole working chain of a VR WebGIS creation process is currently possible on an open source working-chain. The open source applications working on Linux and Windows are exactly the same, so that the portability of the VR WebGIS creation process for different platforms is total. The figure also contains snapshots of the open source applications, showing that such a software works almost totally by user-friendly graphical interfaces. The further step was the specific aim adopted during the developing of the Flaminia VR WebGIS project. In order to completely remove technical problems from the user experience, the creation of pre-compiled software packages is needed. A similar experience has already been done in a Linux environment, which has a complete archaeological working suite: the ArcTeam group developed in the last year a Linux release devoted
Fig. 4 A simple scheme of OSGVisWeb architecture.
4.1 Architecture OSGVisWeb's architecture is composed by 4 principal elements (Fig. 4): Scene Manipulator Handlers (Ext Manipulator): it's a scene manipulator which manages the user events derived from the allocated visualization window. Moreover, it performs modifications on ViewCore's states. ExtManipulator contains, at the moment, two manipulators which can manage in different ways user movements and interactions: LandManipulator allows a macroscopic and fast interaction with selected terrains; Walk Manipulator allows an immersive
interaction simulating a walk-through on terrain (still in a testing phase). Visualization Core (ViewCore): The main feature of such a structure is managing the 3D rendering cycle and a correct creation and modification of the scene tree. Moreover, it manages, at a high level, the user events deriving from the selected Scene Manipulator as well as the web loading of all the models which will compose the scene. To do that, the extension module OSG NET is used. To avoid the problem of the freeze effect on the scene in the previous version (during the loading), a new method of thread-loading has been implemented. ActiveX / Firefox Plug-In Layer (OSGActiveX / npOSG4 Moz): such a middle-range conceptual layer (Fig.4) allows the creation and visualization of 3D rendering windows inside the web pages published by Mozilla Firefox (version 1.5 and newer) and MS Internet Explorer (version 6.0 and newer). It addition, it can be defined as a control flux-manipulator between the 3D render engine and the web pages render engine. Physically, two structures are present to act on these topics: the first is npOSG4Moz creates the windows instances, through WIN32 requests (MS Windows 32/64 bit architectures) and X11 (Linux 32/64 bit architectures), to connect the 3D visualization engine to the Mozilla HTML renderer (Gecko). The second is OSGActiveX; like npOSG4Moz it integrates the 3D visualization engine with the MS Internet Explorer HTML publication engine by MS ActiveX Component technology. Javascript IDL: a Javascript Interface Definition Language which publishes a common methodinterface between the component/plug-in to the web pages, to have a bilateral control flux. Such an abstraction layer allows to send and receive events through a series of control methods. Javascript IDL is completely transparent and allows a web pages development in an independent way if pages are published through Firefox or MS Internet Explorer.
Adding of external 3D models and positioning on terrain by scripting functions. Visible scene visualization by a little 2D map JavaScript “FlyTo” flying function to defined coordinates position. Main menu of interaction with the scene, with “rotation”, “pan”, “zoom”, “FlyTO” (arriving by cursor pointing) and “picking” options and content visualization. Fast content visualization through a pop up window inside the scene (using the “picking” function) External detailed content web page loading (using the “picking” function), for active object on the scene. Javascript function running option by event of Fire type (Only for OSGActiveX) or by HTTP GET requests to the browser. The availability of data tables for each GIS layer, containing all the realization references as well as (downloadable) software and methods used.
4.3 Future development OSGVisWeb is continuously in evolution, and there are studies on possible extensions in many directions. Herby we report some possible next areas of development. • • • • • • •
Studies on ways of maximizing data transfer and implementation of a methodology of catching on disk. Implementation of advanced 3D objects on the scene as avatars, and interaction with them. Multimedia files viewing. Implementation of a methodology of automatic software updating through the web. Linking objects to external databases and publication of informations inside the 3D area. Generation of more 3D layers by informations obtained from spatial databases. Implementation of ways to improve realistic effects on the scene.
4.2 Features
5. Concluding remarks
OSGVisWeb is a viewing platform useful and adaptable to different terrains and 3D models. Among the new features and functions there are: Visualization of web paged terrains and complex 3D models. On-demand terrain loading and switching capabilities during the rendering process of already rendered scenes. Adding and switching of 2D and 3D vector layers in the scene. Adding and switching labels on terrain.
The VR WebGIS Project is an interactive platform aimed at web fruition and based on open source libraries and tools, provided with interface and behaviours. The methodological approach in the use of the platform is oriented towards the public sharing of data, originally available as raw data to a restrict group, with metadata attached (complete references on sources, on software and methods used, etc), for a complete transparency of scientific process, in order to keep reference of the different steps which have led to the final processed information.
Proceedings of “From Space to Place”
Furthermore visibility and availability of data and information are two central concepts, connected to each other, in the open approach. The diffusion of a truly scientific approach to archaeological information is based on the repeatability of processes and on the data and knowledge exchange. On the other side, software availability can represent a good opportunity to enlarge open source community of non programmers, to use and modify specific tools, allowing a faster and further development.
PESCARIN S., CALORI L., CAMPORESI C., FORTE M. 2005, Interactive landscapes reconstruction: a Web 2D and 3D opensource solution, in M. Mudge, N. Ryan, R. Scopigno (eds.), The 6th International Symposium on Virtual Reality, Archaeology and Cultural Heritage, VAST’05 Short Presentations, STAR, Pisa : 33-38 RAYMOND E.S. 1999, The Cathedral and the Bazaar: Musings on Linux and Open Source by an Accidental Revolutionary, Paperback Ed. Rev. O’Reilly, Sebastapol, CA.
Project links: 6. Acknowledgments This paper synthesizes a work developed in the context of a highly interdisciplinary team of CNR ITABC and CINECA Supercomputing Center. For CNR ITABC, the Virtual Heritage Lab team is directed by Maurizio Forte. In the Appia and Flaminia projects worked also Nicolò Dell'Unto, Fabrizio Galeazzi and Valentina Vassallo (archaeologists), Marco Di Ioia, Alessia Moro e Lola Vico (architects), Eva Pietroni (cultural heritage media expert), Claudio Rufa (musician and computer scientist) and Bartolomeo Trabassi (audio/video operator).
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CNR Virtual Heritage Lab.: http://www.vhlab.itabc.cnr.it Appia Project: http://www.vhlab.itabc.cnr.it/appia Flaminia Project: http://www.vhlab.itabc.cnr.it/flaminia OpenSceneGraph website: http://www.openscenegraph.org Virtual Terrain Project website: http://www.vterrain.org
