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
CINECA Supercomputing Centre
Via Magnanelli 6/3
40033 Casalecchio (BO), Italy
CINECA Supercomputing Centre
Via Magnanelli 6/3
40033 Casalecchio (BO), Italy
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" 
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.
User Interface, Navigation Tools, Virtual Reality, History
The history of Bologna is considered significant by the
testimony in its wealth of historical documents . 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historical documents relevant for Bologna in a virtual museum, where it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 . 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
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 , 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 , 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.
. 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  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 .
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.,
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 . 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.
garisenda.wrl: the VRML model of the Garisenda tower
created during the previous three phases;
garisenda.db: a text file which describes the Garisenda
tower's properties that vary with the passing of time. For example, the
information included in the .db files of a building are the dates of construction
where alteration and demolition are specified. At present we have integrated
only existing property, but other properties are foreseen in order to date
reconstruction of façades, restoration of single components, and
survival of earlier elements, etc.
_garisenda.wrl: this file allows the user to select
the VRML model of a building (in this case garisenda.wrl) to visualize
the specific hypertext document garisenda.html.
garisenda.html: this file allows the Nu.M.E. visitor
to isolate the Garisenda tower from its context and examine it individually,
together with the historical resources that were used for its reconstruction.
It is constituted by two HTML frames visualizing respectively: garisenda_bis.wrl
garisenda_bis.wrl: this file is a high resolution
VRML model of the Garisenda tower by itself and not included in the city
model. In this version of the model, it is possible to add light spots
to enhance some components and specific viewpoints.
fonti_garisenda.html: this file is a hypertext document
which describes the historical significance of the Garisenda tower, citing
the sources used to locate it temporally, visualizing its changes from
1200 to the present.
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:
VRML files are in .wrl.gz format (accepted by the VRML browser
the number of pixels which constitutes a complex building
(for example, the "edicola della croce" and the "Asinelli tower and rocchetta")
photo resolution is in reduced and compressed image formats
(GIF and JPG rather than RGB and ARGB),
selecting a building of major importance, the visitor can
choose to open only the HTML document about the historic resources without
visualizing the high resolution VRML model of the building itself.
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 .
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
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 .
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 . 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.
reconstructed and already existent components, architectonic
elements specific of the building itself or typical of an historical period,
portions added or restored, etc.;
historical information to understand better the 4D city tour.
From this point of view it could be interesting to realize an interface
in order to allow the user to choose the historical information to be visualized
visiting the Virtual Museum. The results of this choice could be simple
tourist descriptions, digital editions of historical resources or complex
visualizations of the results of historical research.
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 ,
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.
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.
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Atlante Storico della città di Bologna (in Italian and in English):
Volumes I, II, III, IV, Grafis, Bologna, 1995-98.
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F.Fraticelli, A.Guidazzoli, M.Mariani, The 4 Dimensional City, Science
and Supercomputing at CINECA, 1997 Rep., 408-414.
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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.
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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.
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alt., Time Travels in Virtual Landscapes, SIGGRAPH98 Conference Abstracts
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Virtual Reality Modeling Language and Java, Communication of ACM 41, 6,
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M.E. Bonfigli, The Creation of the Nu.M.E. Project', ACM SIGGRAPH99 Conference
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in Electronic Media, Interactions - New Visions of Human-Computer Interaction
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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,
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