Copyright ACM, 2000

Nu.M.E.: a WWW Virtual Historic Museum
of the City of Bologna

Maria Elena Bonfigli

Dip. Scienze dell'Informazione
Università degli Studi di Bologna
Via Mura A. Zamboni 7
40134 Bologna, Italy
Tel. +39.051.2094880

bonfigli@cs.unibo.it

Luigi Calori

VisIT Lab
CINECA Supercomputing Centre
Via Magnanelli 6/3
40033 Casalecchio (BO), Italy
Tel. +39.051.6171509

calori@cineca.it

Antonella Guidazzoli

VisIT Lab
CINECA Supercomputing Centre
Via Magnanelli 6/3
40033 Casalecchio (BO), Italy
Tel. +39.051.6171509

guidazzoli@cineca.it

ABSTRACT

Nu.M.E., the WWW Virtual Historic Museum of the City of Bologna, is a "four-dimensional" web environment characterized by specific navigation and orientation tools, using virtual reality and interaction techniques to represent VRML real scenarios (the city of Bologna as it is today), VRML artificial scenarios (the city recreated as it was in the past centuries) and their integration. The idea is to realize a link between the concepts of "culture" and "technological innovation" [8] by the creation of a venue being a cultural, scientific and technological meeting point that is both a WWW application and a place in which the city can reclaim its collective identity. On the one hand there is the traditional concept of the museum as a physical venue, and, on the other hand, there is also the opportunity to expose information we have about the historic and urban development of the central area of the city, to visualize it by means of virtual reality, and to distribute it with the use of internet. This new, conceptual reconstruction of the museum allows visitors to look back into time "witnessing" the historical and urban development of the city from the end of the first millennium to the city as it is today. Nu.M.E. can provide also a powerful tool for historic researchers to experiment with and test different hypotheses and to direct access to historic resources necessary for studying the history of the city. Moreover, it offers support for city and regional planners in the decision making process in relationship to urban development, city planning and management, serving as a virtual "test site" for viewing the city in the future.

Keywords

User Interface, Navigation Tools, Virtual Reality, History

1. INTRODUCTION

The history of Bologna is considered significant by the testimony in its wealth of historical documents [1]. Nu.M.E. aims to integrate these available resources in order to render them in the form of a "continuum". This form implies the exploitation of multimedia and virtual reality technologies in order to recreate the historical evolution of the city. Metaphorically speaking, Nu.M.E. enables us to collect the historical documents relevant for Bologna in a virtual museum, where it will be possible to decode them while traveling backwards in time through the city. At the present, the experimental phase of the Nu.M.E. project involves the implementation of a 4D model of an area of buildings located in the temporal dimensions from 1200 to 1999 as well as the area from Piazza di Porta Ravegnana to Piazza Maggiore (shown in Figure 1 below). This area has an important role for Bologna, from a historic point of view due to the fact that it is this part of the city where there is a large concentration of historical resources that are available [1]. This area is also significant from a sociological point of view due to the fact that this area serves as an identity for the city, in Italy, and all over the world.

Figure 1: the area of Bologna reconstructed in Nu.M.E.

In order to create Nu.M.E., we start with the analysis of the existing buildings, reconstructing them in three dimensions. An environment is created in which the visitor can go through the city at street level or fly above the rooftops, to have a birds eye view or close up in order to examine at the scale of detail. This is, in itself, a virtual city [5], because it removes all evidence of modern life (shop signs, road signs, refuse bins, parked or moving cars, etc.), thus allowing the visitor to see the city in its essential elements. This three-dimensional model transforms into a museum when a fourth dimension, time, is introduced. In order to implement the 4D urban model, the historic documents have to be transformed in digital form, also enabling the reconstruction of buildings that no longer exist, the result being, a "realistic" model of Bologna during the past centuries. The establishment of Nu.M.E. consists of a highly, "multidisciplinary" activity requiring the co-operation of different professionals in a wide range of fields. Nu.M.E. is intended not simply to set up a virtual museum of the city of Bologna (that is, a cultural environment to be used by city residents, visitors and schools), but also to make available a model that can be applied to any urban setting, regardless of how many years of history is implied.
The objective of this paper is to show the state of the art implementation of Nu.M.E. in order to realize the idea of a Four Dimensional Digital City [2], translating urban development data derived from historic research information into interactive virtual reality scenarios, available on the Internet. The remainder of this paper is organized as follows. In the next section we describe the historic research role in the settlement of the 4D city model and its implementation phases beginning from 3D models of buildings. In Section 3, we give a brief description of the Nu.M.E interface system and of future works. Finally, Section 4 concludes the paper.

2. THE 4D MODEL

2.1 The fundamental role of historic research

The unique interdisciplinary nature of the Nu.M.E. project is a fundamental and distinguishing characteristic. The idea is to realize an application that could be acceptable both in terms of information technology and historic research. It is necessary to give some examples of what we mean by three-dimensional, virtual reconstruction of old buildings, and what can be done with it from the historical point of view. The first thing is to point out the need to reverse the chronological order of research: instead of starting from the earliest times and working forward, it is necessary to work backwards in time. In fact it is necessary to start from the present day urban setting, which is documented as a unit and in its entirety. Then it is possible to carry out those changes revealed to us by the analysis of historic resources, in order to construct a more "precise" hypothesis concerning the origins of the city and their architectural components always indicating the origin of "scientific deduction". The resulting synthesis is honestly demonstrated by the extreme graphical distinction between what is hypothetical and what is generated directly from historical or present day information whether in the forms of archives or surveys of existing buildings. Thus, these historic resources, in themselves, are extremely important because if they did not exist, this kind three dimensional model could not exist. The result, is in fact a compositions based on a collection of data taken from various fields in order to generate a complete model (bringing together environmental, cultural, and human social factors together) with each component or detail in its rightful place including: facts about architectural details that compose the building structures, information regarding weather conditions, earthquake seismic information, lighting factors in both public and interior spaces, structural components of building constructions and their reaction to sunlight and weather factors, etc. [4]. On the other hand, research in general, especially in the field of urban historians, will greatly benefit from the application of this type of four dimensional model. With this type of representation consolidating various data about the city, it is then possible to explore issues regarding about "gaps" in urban history. This complete representation of the city, as a result, will benefit historians or any researchers in the fields of urban history allowing them to explore areas of the history of the city that is yet to be considered. By solely reconstructing a building graphically, it is necessary to include the following information in order to consider as many details as possible: the height of the building, the number of columns, the apertures in the walls, materials of construction, etc. In this process it is also necessary to include information about: the morphology of the roofs, the interior courtyard spaces, the height of porches, or portici, and the morphology of vaults. The need to collect this data requires and stimulates continuous historic research in more detail so as to identify new resources and compare them to existing data already collected. This type of research and especially its particular graphic representation of historic material obliges the historian to assume a different work methodology. Aside from this new role in Nu.M.E. development, the historian also assumes a point of intellectual impulse that stimulates and later verifying the development of hypothesis concerning the city. To make sure that the visitor understands that, during the their navigation through the four dimensional city, he is seeing only as much as the historical sources can justify, each element it is composed of (such as buildings, districts, etc.) are all accompanied by link references in HTML format, compiled directly by the historian. These references can be easily accessible and consulted at any time during the visit.

2.2 The implementation phases

The idea of making Nu.M.E. accessible on the Internet arises the necessity to facilitate interaction between historic researchers as well as to reach a great number of users. For this reason and in order to develop dynamic and interactive 3D environments in a portable, standardized, platform independent manner [6] we chose to implement Nu.M.E. with VRML and Java languages. Briefly the implementation process of the Nu.M.E. project consists of a progressive introduction of 3D models of buildings in the virtual 4D city model. This process can be subdivided in four phases (shown in Figure 2): (1) the translation of CAD models into VRML models; (2) the location of VRML models in the spatial dimensions: the "3D world"; (3) the graphic processing of VRML models in order to render them "photo-realistic"; and (4) the location of VRML models in the temporal dimension: the fourth dimension [7].

Figure 2: The implementation process phases

During the translation phase, a CAD model of a building must be translated into VRML format. This involves the processing of all the CAD solid models in which some must modified in the following manner: (a) to maintain only the surface information useful in the VRML representation, that is, for example, to eliminate the surfaces non directly visible by an observer outside the virtual building. (The more details the building model has, the longer the VRML browser takes to reconstruct it, and the less interactive it becomes); (b) to introduce a hierarchy among the different components which constitute a building, so that during the graphic processing phase, it will be possible to operate them singularly and to reproduce their temporal evolution if required as a separate entity from the rest of the building.
During the spatial collocation phase, the VRML model of the building is inserted in the area of the city recreated in the Nu.M.E. project considering only the spatial coordinates. This is later translated, rotating it in order to locate it in the correct position. Recently, we introduced the possibility of viewing a 3D model of this area in order to locate the buildings also at the correct height.
During the graphic processing phase the VRML files are processed in order to render them photo-realistic. A detailed reproduction of all the geometric, 3D models which constitute a building results in a slow viewing process of the global, virtual world. In order to improve performance in terms of download time or of frames per second, we use photos as texture applied to simplified 3D, single, architectonic elements (for example roofs, porticoes, columns, etc.) and buildings. Moreover, each element or building is created in multiple versions, with a level of detail that increases with the proximity to the building: the closer the visitor approaches to the building, the more detailed the 3D reproduction becomes. It is necessary to consider a balance between an accumulation of details to achieve maximum realism and simple drawing models to insure maximum interactivity. It is worth to note that for the buildings that no longer exist, we have often detailed written resources that provide a list of important information about the buildings: the number of flats, the presence of arcades, the distance between two buildings, etc.[3], but it is hard to find photos, miniatures, paintings describing the building’s appearance. In these cases we have to represent only the building’s geometry using polygon faces without textures. In fact the main aim of the NuME project is to reconstruct only as much as historical resources can justify.
The final implementation phase consists of positioning the building in the temporal dimension. In Nu.M.E., each building is identified by: (a) the VRML model created during the previous three phases; (b) some properties that vary with the passing of time, starting with the initial appearance of the building; (c) the historical resources justifying the four-dimensional reconstruction of the building [7]. From the implementation point of view, we associated each building to a set of different files dynamically managed by the Nu.M.E. interface system. This point may be illustrated by the following outline of the files associated with the Garisenda tower to serve as an example:

Figure 3 below shows the file garisenda.html. In the first frame Dante's point of view of the Garisenda described in The Divine Comedy is visualized; in the second frame two Dante's descriptions of the Garisenda tower are quoted.

Figure 3: the file garisenda.html visualizing respectively the files garisenda_bis.wrl and fonti_garisenda.html

3. THE 4D INTERFACE SYSTEM

The Nu.M.E. interface was designed in order: (a) to allow the user to visit a virtual reconstruction of Bologna that could be "acceptable" in terms of display speed and graphic resolution for every type of user; (b) to provide the user with simple and efficient navigation tools to visit the city in four dimensions.

3.1 The high resolution and the light models

The Nu.M.E. project has a great variety of potential users. Clearly a historical researcher needs a 4D visualization more detailed than the average virtual tourist. On the other hand a virtual tourist, who is connected to the Internet with a standard PC and modem is likely to give preference to a higher velocity of access rather than to the careful reproduction of too much detail. Because of this factors, we provided two different ways of accessing Nu.M.E.: one, using a LAN connection or a visualization in a local virtual environment, and one using a remote connection to the Internet. In particular, we integrated two models respectively: (a) the high resolution model, available locally at CINECA Visit lab and at a public kiosk in Piazza Maggiore: the main square in Bologna, and (b) the light model, available at http://www.cineca.it/visit/NUME. The two models have different level of details in which 3D models and multimedia data are stored having a different resolution, but the same level of historic authenticity. Briefly, in the light model (2 Mb), unlike the high resolution model, the following occurs:

3.2 Navigating in four dimensions

In the Nu.M.E. prototype, the spatial and temporal dimensions are two distinct entities. VRML allows graphic designers to create 3D objects and to add simple characteristics to those objects. In order to allow more, complex behaviors depending on outside data or user interaction, we used External Authoring Interface (EAI) to control the VRML world externally with a Java applet. The choice of VRML and Java guarantees equal conditions of access for all platforms [6]. The prototype consists of a VRML browser for the 3D display, and Java applets for implementing specific Nu.M.E. interfaces 4D interaction and orientation tools (see Figure 4 below)

Figure 4: The Nu.M.E. User Interface

These tools, active both for the high-resolution virtual city and for the more basic version are actionable with direct manipulation objects and aim to improve management of either spatial navigation or temporal navigation.
The Nu.M.E. Console spatial navigation tool is a two-dimensional orientation map of the area of Bologna reproduced in the Nu.M.E. project allowing visitors to visualize their position in the virtual world with a red rectangle and the direction of observation of the city with a green rectangle. The map can be shown or hidden by means of a button on the console [3].
The temporal navigation tool is the time-bar. It consists of a text field showing the year on display and a bar with a cursor showing the time line [3]. Through the "time bar", visitors can select the historical period in which they wish to take their virtual walk through the city. By selecting a year, it is possible to visit the city in its entire reconstruction. Each time a year is entered in the text field or when the cursor is moved, the virtual world is dynamically updated (e.g. Figure 5, 6 and 7 below, show how the "two towers" look like in three different periods).


Figure 5: The "two towers" in the XIII century


Figure 6: The "two towers" in the XIX century


Figure 7: The "two towers" in the XX century

In particular moving the time-scrollbar (or typing an year in the text-field), a Java applet causes an event to be sent, through EAI, to the VRML world changing the Existence property of each Building Java class. This feature provides a method that interacts with, and dynamically updates the VRML world in order to obtain a new scene according to the historical age chosen by the user. This new scene is performed by loading the buildings that existed in that age and unloading the others on the basis of the information accessed in the .db files (see subsection 2.2). The .db file of each building contains (a) a systematic list, coded in reverse chronological order, of the years in which the building has been changed (e.g. built, destroyed, restored, etc.); (b) the VRML models to be loaded for each time range. Otherwise, the hypertexts related to each building are directly reachable following links connected to the building itself in the VRML scene.
With regard to user orientation in temporal navigation, we also introduced in the virtual world a sound environment, in which each century is associated with a different sound-track. This strategy allows visitors to identify, at intuitive and perceptive levels, the period in which they are visiting the city.

3.3 Future works

Recently, we have begun to build a single database in order to integrate and to structure better the data collected both in the .db files and in the hypertexts. The idea is to define for each building a hierarchical structure that includes: Future works will regard also the realization of a new immersive physical access to the Nu.M.E. scenario in order to prepare a Virtual Theater using technologies like the Reality Center SGI. From the technological point of view, two essential characteristics must be considered: immersion and interaction, high quality graphics with photo-realistic characteristics. There is reason to believe that the virtual theater could be the natural development of our High Resolution Model.

4. CONCLUSIONS

The creation of Nu.M.E. brings together many integrated aspects: (a) the concept of historical evolution combined with the concept of cultural identity, and (b) the concept of technological innovation with the concept of information society. The advantages of interacting with NuME include the possibility to reconstruct buildings that no longer exist or that exist partially, to simulate viewpoints that are not accessible in the reality, and to interact with virtual reproductions of art works directly without the risk of degradation. In particular these advantages can be useful both for historical researchers and for general public. On the one hand NuME provides researchers with  graphics tools to experiment with and test different hypotheses, giving them the possibility to visualize data extrapolated by written, pictorial or archeological resources in a new perceptive manner. On the other hand the use of NuME can improve interests, curiosity and knowledge of the history of the city [4], giving access to data not commonly available: putting together 3D objects that are not in the same place in the reality, and of which only fragments remain or also anything but historic documentation.

5. ACKNOWLEDGMENTS

Authors wish to thank the Scientific Director of the NuME Project Prof. Francesca Bocchi, Manuela Ghizzoni, and Rosa Smurra (Department of History of the University of Bologna) for their historical researches; the Consorzio Università-Città for its coordination activity and the Bologna City Council for supporting the NuME project.

6. REFERENCES

[1]    F. Bocchi (ed.), Atlante Storico della città di Bologna (in Italian and in English): Volumes I, II, III, IV, Grafis, Bologna, 1995-98.

[2]    F.Bocchi, L.Calori, F.Fraticelli, A.Guidazzoli, M.Mariani, The 4 Dimensional City, Science and Supercomputing at CINECA, 1997 Rep., 408-414.

[3]    F. Bocchi, M.E. Bonfigli, M. Ghizzoni, R. Smurra, F.Lugli The 4D Virtual Museum of the City of Bologna - Italy, ACM SIGGRAPH99 Conference Abstracts and Applications (Los Angeles - USA, August 1999), pp. 8-11.

[4]    M.E. Bonfigli, A. Guidazzoli, A WWW Virtual Museum for improving the knowledge of the history of a City, in Virtual Reality in Archaeology, J.A. Barcelo, M.Forte, D. Sanders (eds.), ArcheoPress, in press.

[5]    I. Braun & alt., Time Travels in Virtual Landscapes, SIGGRAPH98 Conference Abstracts and Applications (Orlando – USA, July 1998), 283.

[6]    D.Brutzman, The Virtual Reality Modeling Language and Java, Communication of ACM 41, 6, 57-64.

[7]    A. Guidazzoli, M.E. Bonfigli, The Creation of the Nu.M.E. Project', ACM SIGGRAPH99 Conference Abstracts and Applications (Los Angeles - USA, August 1999), 31-32.

[8]    K.H. Veltman, Frontiers in Electronic Media, Interactions - New Visions of Human-Computer Interaction IV, 4 , 32-64.

BIOGRAPHIES

Maria Elena Bonfigli is a Ph.D. student in "History and Computing" at University of Bologna, Italy. Her research interests include: Distributed Multimedia Systems, Teaching/Learning Environments, 3D Web Interface Design and Virtual Reality applied to Cultural Heritage.

Antonella Guidazzoli is a Computer Scientist at the VIS.I.T. lab: the interdisplicinary laboratory at CINECA. Main research interests: Computer Graphics and Image Processing Techniques, Virtual Reality applied to Cultural Heritage, Forensic Applications.

Luigi Calori is a Computer Scientist at the VIS.I.T. lab. Main activities: Computer Graphics, Image Processing, Scientific Visualization, Medical Imaging.

Copyright 2000 ACM

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