3D TECHNIQUES TO CREATE INTERACTIVE VIRTUAL

MUSEUMS: THE STATE OF THE ART IN THE EPOCH NOE

Denis Pitzalis, Christian Lahanier, Genevieve Aitken and Ruven Pillay

Centre de Recherche et de Restauration des Mus

ees de France,

14 quai Franc¸ois Mitterrand, Palais du Louvre, Porte des Lions, 75001 Paris, France

Karina Rodriguez-Echavarria and David B. Arnold

University of Brighton

234 Watts Building, Moulseccomb, Brighton, United Kingdom

Keywords:

Interactive Environments, Real-time Graphics, Graphics Application Pipeline, Technology in Museums.

Abstract:

Information and multimedia, such as images or 3D models, stored in databases are very important to preserve

the information about historical artefacts and works of art. Nevertheless, the potential of digital content in

databases is not fully exploited until it is used to create interactive ways to communicate to non CH specialist

the signiﬁcance that these objects have. 3D virtual environments are a suitable mechanism for giving context

to, otherwise isolated, pieces of information. To achieve this, different techniques for 3D acquisition, inte-

gration and visualisation must work together in order to create 3D interactive virtual environments which are

engaging and accessible for the visitors of a muse um. In this paper we will describe the state of the art of the

techniques for achieving this type of environments within the partners of the EPOCH Network of Excellence.

1 INTRODUCTION: WHY

BUILDING VIRTUAL

MUSEUMS?

The role of museums is shifting from that of an insti-

tution which mainly collects and stores artefacts and

works of art towards a more accessible place where

visitors can experience heritage in more engaging and

interactive ways. As such, information and commu-

nication technologies have great potential for assist-

ing not only in the documentation and preservation of

information, such as images or 3D models about his-

torical artefacts and works of art; but also for creating

interactive ways to communicate to non CH special-

ists the signiﬁcance that these objects have.

The concept of technology as another medium for

representing heritage extends to all digital technolo-

gies in museums. For example: audiovisual guides,

interactive multimedia screens and 3D interactive vir-

tual environments. These mediums potentially pro-

vide a better understanding by contextualising arte-

facts in the museum in time and space and comple-

ment other forms of more traditional media, such as

books, artist reconstructions, or photography, deal-

ing with representations of the past (Thornton and

Rodriguez-Echavarria, 2006). In particular, 3D in-

teractive virtual environments are a unique medium

for representing heritage as they are able to provide

a semi-realistic representation of 3 dimensional ob-

jects/spaces. This makes them a suitable mechanism

for giving context to, otherwise isolated, pieces of in-

formation or physical objects which, at the moment,

are displayed in glass cabinets or on museum walls.

Hence, they enable visitors to interact virtually with

historical objects, which will not be otherwise acces-

sible due to their nature and fragility (Lahanier et al.,

2002).

It has to be recognised, however, that the creation

of Virtual Museums based on existing digital data-

bases is more viable for larger Cultural Heritage in-

stitutions, who have more resources for the digitisa-

tion process, digital databases and the types of in-

stallation that virtual environments require. Medium

and smaller institutes might ﬁnd that the use of

other mechanisms for representation are more suit-

able, such as audio-video story telling or much sim-

pler multimedia applications. Nevertheless, it is ex-

pected that as the price of digitisation drops, and the

cost of acquisition and maintenance of hardware and

software becomes more accessible, more museums

will increasingly be able to experiment with this type

197

Pitzalis D., Lahanier C., Aitken G., Pillay R., Rodriguez-Echavarria K. and B. Arnold D. (2007).

3D TECHNIQUES TO CREATE INTERACTIVE VIRTUAL MUSEUMS: THE STATE OF THE ART IN THE EPOCH NOE.

In Proceedings of the Second International Conference on Computer Graphics Theory and Applications - AS/IE, pages 197-203

DOI: 10.5220/0002085201970203

 SciTePress

of environment.

The process of building a 3D virtual museum

draws on many different technologies and digital

sources. From the perspective of the Computer

Graphics professional, technologies such as pho-

togrammetry, scanning, modelling, visualisation, user

interfaces, run-time engines and interaction tech-

niques need to all work together. Additionally, the

data exchange formats become essential to ensure that

the digital sources are seamlessly integrated in the ﬁ-

nal experience. These domains need to interoperate

efﬁciently and transparently in order to create engag-

ing ways of presenting information.

This paper will present the state of the art of such

techniques for creating 3D virtual museums within

the partners of the EPOCH Network of Excellence

(EPOCH, 2002). In addition, it will report on some

concerns with, and propose some solutions for, the

integration of the technologies previously mentioned.

A case study proposed by the Centre de Recherche et

de Restauration des Muses de France (C2RMF) will

be presented to illustrate the integration of real tools

for digitising and creating a 3D virtual environment,

which takes advantage of the 3D documentation of

works of art.

2 DIGITISATION PROCESS

Museum artefacts can vary greatly. They can be, for

example, books, documents, statues, paintings and

works of arts. As such, they are all made of dif-

ferent materials, with different shapes and sizes. It

is also necessary to consider other types of 3D Cul-

tural Heritage content, such as terrain data, archi-

tectural sites, virtual avatars, ﬂora, fauna, as well as

other types of content (i.e. video and sound), in or-

der to portray more effectively the historical context

of an object. Hence, different techniques for digiti-

sation are required. The following subsection will

describe three techniques, different in terms of cost,

time and methodology, which are, at the moment, the

most widely used means of capturing digitally the ob-

jects of a museum: photogrammetry, 3D laser scan-

ning and modelling.

2.1 Photogrammetry

The goal of this system is to reconstruct a 3D ob-

ject from a sequence of geometrical and colour cal-

ibrated images. The method used at the C2RMF

is called shape from silhouettes (Hernandez-Esteban

and Schmitt, 2003). The 3D digital photography

capture system, developed in 2000 for the ACOHIR

project (Martinez et al., 2000) consists of an accu-

rate turntable to support the object, a simple digital

camera, a professional lighting system and a PC to

synchronise the acquisition. The computer controls

the step by step rotation of the turntable, the lighting,

the digital capture and the transfer of the ﬁles to the

hard disk. At each step a digital image of the object is

saved in sRGB in high deﬁnition (4000x5000 pixels)

(Figure 1). The number of angular steps per rotation

(usually 24 or 36 steps) can be changed. For complex

objects several sequences can be acquired at various

inclination angles of the camera to get a more com-

plete panoramic view. A colour chart image is then

used to calibrate the camera and to correct the colour

of images.

Figure 1: Glass vase, Buballo Lucio (Venice), Mus

ee de

evres, inv. MNC27731. 3D model obtained by pho-

togrammetry process.

When the set-up is complete for a given set of ob-

jects with similar shape and size (camera positioning

for distance and inclination, zooming and focus, light-

ing) we proceed to a geometric calibration of the ac-

quisition system before the object capture. The cali-

bration can be performed in two ways: the ﬁrst one,

more secure but slower, is by acquiring several digital

images of a black geometric target containing bright

circular patches and by placing it in different posi-

tions and orientations on the turntable; the second one

is entirely based on the silhouettes extracted from the

image.

The use of silhouettes requires an accurate extrac-

tion of the object from the background, which is not

always an easy task. The calibration allows us to ob-

tain high resolution image sequences with a strictly

controlled geometry. From the calibrated sequence of

an object we can reconstruct a 3D model of the object

with its colour texture. To do so, we use several types

of information contained in the images. We ﬁrst ex-

tract from each original colour image the silhouette of

GRAPP 2007 - International Conference on Computer Graphics Theory and Applications

198

the object. Then we build in the 3D space a volume

called the visual hull which is an upper-boundary of

the real object volume. The visual hull is then carved

in order to recover the missing concavities of the ob-

ject surface. At the end of the process we are able to

recover the apparent contours of the model. Finally, a

texture map is computed from the original images for

the reconstructed 3D model (Lahanier et al., 2004).

Another tool available for photogrammetric re-

construction is the EPOCH 3Dmodel web service

(Vergauwen and Gool, 2006). This tool allows users

to upload digital images to a service where a partial

3D model of the scene is reconstructed using shadow-

based photogrammetry techniques.

2.2 3D Laser Scanning

A more expensive way to digitise an object is by ac-

tive 3D laser scanning. The fast capture time of a

view (from 150,000 to 300,000 triangles with a Mi-

nolta VI900) allow the user to take many digital shots

to cover all parts of the object. If the object is small,

we can use a normal turntable to change it’s orien-

tation more quickly. The resolution of the MINOLTA

camera is 100µ for x and y and 50µ in depth (Lahanier

et al., 2005). The texture is acquired simultaneously

by means of an internal video camera without colour

calibration. The reconstruction of the object can be

performed using MeshLab (MeshLab, 2006). Mesh-

Lab is an open source system for editing, cleaning,

healing, inspecting, rendering and converting unstruc-

tured 3D triangular meshes.

Recently a new system has been tested at the

C2RMF to scan paintings (Figure 2). This technique,

developed by the Canadian National Research Coun-

cil is based on the direct acquisition by multiple low-

power lasers (Taylor et al., 2002). The system scans a

small (less than 100µ diameter) white laser spot from

three (RGB) laser sources over the complete surface

of an artefact, for example a painting. A triangula-

tion based detection system simultaneously records

the spatial measurements (x,y,z) and the colour re-

ﬂectance (RGB) from the spot. The maximum lateral

resolution is of 50µ with a depth resolution of 10µ.

A unique feature of this technology is the ability

to examine the surfaces and roughness of paintings as

well as the overall shape of canvas and panel paint-

ings. The shape data recorded by the scanner origi-

nates from the immediate surface of the paint layer,

under the varnish, rather than from the varnish sur-

face. This results in a detailed high-resolution record-

ing of the surface relief or 3D structure of the paint

layer from brush stroke details as well as from craque-

lure formations due to ageing.

Figure 2: Naked woman, detail, Renoir Pierre Auguste, Mu-

seum of l’Orangerie, inv. RF 1963-13. 3D model obtained

by color laser scan.

2.3 Modelling

Modelling is another technique where 3D polygo-

nal representations of object are constructed either

by hand or algorithmically, which includes genera-

tive and procedural modeling. Techniques for algo-

rithmic modelling include: generative (Berndt et al.,

2005a; Berndt et al., 2005b), procedural and rule

based (Wonka et al., 2003; Mueller et al., 2006;

Mueller et al., 2005). Other techniques are (Plat-

ings and Day, 2004) for landscape and (Ciechomsky

et al., 2005; Ryder et al., 2005; Thalmann et al., 2005;

Wilkinson et al., 2004) for avatars modelling (Figure

3).

Figure 3: Animating Virtual Humans Modelling example.

3D TECHNIQUES TO CREATE INTERACTIVE VIRTUAL MUSEUMS: THE STATE OF THE ART IN THE EPOCH

NOE

199

3 INTEGRATION OF THE 3D

DIGITISED CONTENT

Once the artefacts have been digitalised, it is neces-

sary to integrate them with other CH content and add

interactivity. To do this different techniques are avail-

able and this is the stage where the integration of the

different technologies is most critical.

The decision of which objects, content and inter-

activity to include is tightly coupled with the target

public and the requirements of the application. One

of the critical aspects of this stage is to ensure con-

tent reusability. This is especially the case as the role

of technology in museums shifts towards achieving

a “ﬂexhibit” conﬁguration approach (Tolva, 2006).

In this approach, content is used in reconﬁgurable

spaces, such as immersive virtual environments, mul-

timedia, on the web, or on mobiles, by using different

types of presentation technologies. Hence, reusability

is essential as it will provide maximum ﬂexibility and

will avoid repeating the work for use within differ-

ent contexts. To automate this, previous approaches

include the use of presentation domains (Patel et al.,

2003), which correspond to different environments in

which the digital artefacts can be used.

Cultural Heritage 3D interactive environments

have normally been handcrafted (Calori et al., 2003;

Gaitatzes et al., 2004; Ch’ng et al., 2004) using

device-independent graphics libraries (e.g. OpenGL

(OpenGL, 2006)), scene graph based libraries (e.g.

OpenSG (OpenSG, 2006), OpenScenegraph (Open-

SceneGraph, 2006), Performer (Performer, 2006)),

game engines for integrating content (e.g. Un-

real Tournament (UT, 2006), Aurora toolkit (NWN,

2006)) or 3D authoring tools (Rodriguez-Echavarria

et al., 2005; Laycock and Day, 2003). Although this

affords a great degree of freedom, it also requires ex-

perienced graphics professionals as developers (Fig-

ure 4). As a consequence museum curators or other

CH professionals who may not have this experience,

are unable to participate fully and the development

focus can be diverted from creativity to technology.

For this reason, it is important to involve curators and

museums designers at this critical stage of the devel-

opment process.

Integration also requires the translation of con-

tent data formats from the original applications to a

format that can be used to stitch content together.

Almost all applications for creating content rely on

proprietary data formats that can only be reused by

making translations which require inefﬁcient modiﬁ-

cations to the ﬁles. Although a lot of work has been

done in this area, since the ﬁrst attempts to deﬁne ISO

standards for computer graphics (Arnold and Bono,

Figure 4: Authoring tool example.

1988), there is still a lack of international commonly

accepted standards for exchanging 3D data, such as

generalised scene topology, individual models and be-

havioural mechanisms, as well as offering ﬂexibility

for custom components. This is specially important

for Cultural Heritage artefacts in museums, where the

conservation of the data well beyond the lifetime of

current systems is essential. Currently, X3D (suc-

ceeding the earlier VRML) and COLLADA (COL-

LAborative Design Activity) are two popular stan-

dards for encoding 3D objects into common formats

for sharing between applications. COLLADA is in-

creasingly used in 3D content creation whilst X3D

has particular legacy value and familiarity in the ﬁeld.

Both formats can encode a scene using an XML syn-

tax. Some of their main differences are:

• X3D (Web3D Consortium 2006) is an ISO stan-

dard, while COLLADA was originally established

by Sony and then adopted by other main players

in the gaming industry. These will have an effect

on which applications will take advantage of these

formats as they are being directly supported by the

tool vendors.

• COLLADA is designed as an interchange format,

while X3D is designed as a content deployment

format, targeting web type applications.

4 VISUALISATION OF 3D

INTERACTIVE VIRTUAL

MUSEUMS

Technologies for visualisation are constantly being

developed and at the moment no single technology

can fulﬁl all applications. Such technologies vary in

size, shape, stereo capability, cost, type of view (di-

rect view vs. projection) and their usage depends

on the speciﬁc characteristics of the installation. Re-

cently, popular visualisation installations in museums

GRAPP 2007 - International Conference on Computer Graphics Theory and Applications

200

have focused on single or multiple projection archi-

tectures, including CAVE based environment (Rapp

and Weber, 2005; Christopoulos et al., 2001). These

environments usually consist of projection screen in-

stallations, stereo surround sound and other devices

for users to interact with the environment. Another

type of installation consisting of a video wall using

direct view screen technologies instead of projection

systems is starting to emerge and is also gaining pop-

ularity. The visualisation of 3D interactive virtual mu-

seums provides a set of unique challenges for visual-

isation technology, as this types of environments:

• Integrates content from a mixture of acquisition

techniques and thus may contain a mixture of

large meshes.

• Require interactive frame rates for the visitors to

engage with the application.

• Require different rendering techniques in case dif-

ferent modelling approaches had been used.

Techniques such as cluster based visualisation

might be a solution for this need. This technique in-

volves a cluster of standard PC’s driving an array of

projectors or screens, where each PC is responsible

for rendering a predeﬁned part of the display. The

reason for its suitability are mainly:

• the low hardware and software acquisition and

maintenance costs

• the power of modern graphics cards, driven by

the computer video games industry, now rival the

more powerful graphics engines.

By using this technique, a layer of software is still

necessary above the operating system and below the

application level to provide synchronisation of input

devices and the 3D environment. For this, the mecha-

nisms that are available include: OpenSG, Chromium

(Chromium, 2006) and Equalizer (Equalizer, 2006).

5 A CASE STUDY:

GALLO-ROMAN WHITE CLAY

FIGURINES

During the Gallo-Roman period (from 40 to 300 AD),

numerous workshops in the Centre of Gaul produced

white clay ﬁgurines made of kaolin. More than 5,800

ﬁgurines are registered in the EROS database at the

C2RMF(Aitken et al., 2005). The knowledge ac-

quired on the production of these artefacts and the ex-

tension of its diffusion conﬁrms the role of the ancient

commercial routes of the Roman Empire and the reli-

gious inﬂuence between civilisations from the North-

ern and Southern French countries.

Figure 5: A “Venus Anadyomene” and it signed mould.

Anne de Beaujeu Museum, Moulins, France.

The ﬁgurines production starts by the modelling

of a “genotype” or “archetype” made by the “coro-

plathe”. Then, by casting the genotype, its shape was

extracted using prints to make moulds; the number of

which depended of the complexity of its shape (3 for

a Venus comprising the two pieces for the front, the

back and the base; 13 pieces for a Spinario). The sev-

eral moulds extracted from a genotype are generally

signed on their outer part to identify the name of the

producer or that of the moulder. Then, after drying

the moulds, a great number of copies can be stamped.

The different pieces are joined and glued with diluted

clay called “barbotine” to rebuilt the empty ﬁgurines

similar to the genotype. In order to prevent the model

from exploding during the ﬁring process, a small hole

is made in the back of the fresh ceramic to evacu-

ate the pressure of the vapour. During the drying

and the baking process the objects shrink. When the

genotype and the moulds are worn, new castings are

made using the existing ﬁgurines. This process pro-

duces generations of artefacts which are progressively

smaller (approximately 10% reduction each time). To

study the production and the spread of these artefacts

throughout Gaul and in the Roman Empire, archaeol-

ogists have built a typology of the different kinds of

God, Goddess, ﬁgures, animals, fruits, aliments and

toys, etc. As the objects were dispersed and broken,

the classiﬁcation consisted of designing and describ-

ing the incomplete models. It was a single historian

that had to perform this classiﬁcation in order for it

to be coherent due of the subjective visual aspect of

this method without 3D measurement. To automate

this process, an electronic inventory and 3D mod-

elling were coupled with the chemical analysis of the

3D TECHNIQUES TO CREATE INTERACTIVE VIRTUAL MUSEUMS: THE STATE OF THE ART IN THE EPOCH

NOE

201

clay made at the C2RMF on few thousands of the ﬁg-

urines.

One of the focal points of the French national

project “Metamorphose” was to present C2RMF re-

sults to the public in an exhibition. The use of a Vir-

tual Museum was a suitable solution to this need, as

most of the ﬁgurines were already digitised and clas-

siﬁed in a database. The digitisation involved laser

scanning techniques for the artefacts and modelling

techniques for the virtual environment (Figure 6). The

application was rendered using OpenGL and visu-

alised by the users using a single PC display. The

main objective of the application was to contextualise

the reconstructed 3D ﬁgurines in a virtual environ-

ment representing the original workshop. The reason

for this, was to show the visitors not only the ﬁgurines

but also, their history and characteristics as well as the

processes used for their production. This allowed vis-

itors to experience how the past might have been for

that particular society, and understand the production

techniques as well as gain new knowledge of the era.

Figure 6: Animating Virtual Humans Modelling and Au-

thoring tool example.

6 CONCLUSIONS

Within the Cultural Heritage domain access is so lim-

ited that the opportunity to create digital representa-

tions is precious. For this reason, it is crucial that con-

tent already existent should be fully integrated into ef-

fective means of presentation. This paper highlighted

the importance of using information and communi-

cation technology as a more effective media for rep-

resenting heritage. Although, it was recognised that

museums which already have databases with digital

artefacts might take better advantages of creating this

type of environments for visitors to better appreciate

the artefacts’ value. The paper presented an overview

of the techniques which are available for creating a

3D interactive virtual museum. The different tech-

niques for digitisation, integration and visualisation

were described. In addition, several issues with the

current development cycles of interactive experiences

were identiﬁed. These issues might not only apply to

the Cultural Heritage application area, but for many

others; hence, its consideration is important. The pa-

per highlighted the importance of the content integra-

tion stage of the process and the need for common

guidelines as well as the adaptation of general pur-

pose standards, which are necessary for all different

techniques to work together efﬁciently. Finally, the

potential of using content in existing databases, such

as the C2RMF EROS database, was used as an exam-

ple of how virtual environments is an area which is

still to have a greater impact on the way that visitors

experience museums today.

ACKNOWLEDGEMENTS

Part of this work has been conducted as part of the

EPOCH Network of Excellence (IST-2002-507382)

within the IST (Information Society Technologies)

section of the Sixth Framework Programme of the Eu-

ropean Commission.

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