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27
and `virtually real' representations. The idea
is to display the collection of a particu-
lar library with a default metaphor chosen
as the most appropriate by the librarian. At
the moment, only cylindrical and spheri-
cal collections are generated `on the fly' in
VRML file format by a CGI script (see
Figure 2). A default sort method for books
would also be chosen when entering the
library for the first time, but the user could
change those settings to increase his ease of
use or efficiency.
The reading tool
Our first try was to represent, using a
scripted VRML file, the collection and the
books enclosed in 2D transparent windows
(see Figure 3b.)20. We thought that nov-
ice 3D users could benefit from this well-
known 2D metaphor for organising a 3D
environment. However, it appears that these
containers are too limiting compared with
3D metaphors.
U
sing 3D models instead of 2D com-
ponents is the best solution to obtain
more meaningful visual effects. We do not
necessarily need a `virtually real' book but,
instead, a book metaphor (Figure 3a) that is
more practical and comprehensible at first
sight. Interactions with this object are easi-
er to understand and are much more pow-
erful. For example, a tool can be provided
for rolling pages automatically as happens
in Web books.21 It is an intuitive way to
acquire the structure of a book and, as with
a real book, it provides a quick means of
finding pages of interest (those with imag-
es or mathematical formulae, for example).
Interacting with 3D objects could lead to a
sophisticated but powerful interface. Thus,
we have abandoned this first VRML proto-
type for the book metaphor. The first 3D
interface, developed in VRML and Java,22
was presented on the CNum site as an
alternative solution to the usual HTML-
based reading. However, the difficulties
when programming interactive behaviours
with this language led us towards some 3D
API (OpenGL) and middleware technol-
ogies, e.g. Virtools (http://www.virtools.
com/) and Criterion Renderware (http://
www.renderware.com/).
INTEGRATION METAPHORS
T
he activities of browsing through
collections and reading content are
separated in most present Web-based dig-
ital library interfaces. This context break
induces longer apprenticeship and naviga-
tion time within the interface. Hence, we
also studied how 3D interaction metaphors
could be used to provide a continuous nav-
igation space for these two tasks.23 Two
options are possible for integrating brows-
ing and reading activities: first, to mix their
content; second, to separate them in space
and use a 3D metaphor to switch from one
to the other. We have sketched such navi-
gation metaphors. The figures below were
described and rendered using the ray-trac-
ing program POV.24 In the three integra-
tion metaphors, the basket (shown in the
three Figures 4, 5 and 6) is the only com-
mon tool, always visible and in the fore-
ground. It serves as a link between both
interfaces. It is used to group the pre-select-
ed books chosen in the collection interface,
to access them in the reading interface, and
also to save the user's session.
The cockpit metaphor
The scene's background comprises the
collection (Figure 5). The basket and the
opened books are in the foreground. They
are always visible and are not affected by
the user's navigation. In a similar fash-
ion to a pilot flying over a landscape while
Fig 3a: The book metaphor
Fig 3b: Screenshot of the VRML prototypal application
20 This prototype application in VRML can be seen on our
Web site: http://cnum.cnam.fr/vrml or, for more information,
see P. Cubaud and A. Topol, `A VRML-based user interface for
an online digitalized antiquarian collection' in Proceedings of
ACM Web3D`2001, Paderborn, Germany, February 2001.
21 See Card et al. (1996).
22 See Cubaud et al. (1998).
23 See P. Cubaud, P. Stokowski and A. Topol, `Mixing
Browsing and Reading Activities in a 3D Digitalized Library',
Joint Conference on Digital Libraries 2002, Portland, Orgon, USA,
June 2002.
24 Some animations were also computed and are accessible on
our Web site: http://cnum.cnam.fr/.

CNAM,

2004

CNAM,

2004