Chapter 8. 3D Interaction for Digital Libraries
8.3. The book and reading interfaces
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Figure 8.5. 3D surface translated into VRML, unflattened text in order to remove the false correlations
3D Interaction for Digital Libraries 131 quotes and notes also play a key role in academic-type publications. Sequential reading is therefore relatively rare, and these books are rarely read on their own.
We have tried to take this information into account in the definition of the interface of the CNUM:
– the user can easily open several windows in order to navigate amongst several facsimiles of texts or search through their tables;
– zoom functions enable the user to modify the current page to the size of the window which contains the page;
– specific navigation tools have been created in order to move from shelf to shelf or to go directly from any page to a particular shelf mentioned in this page.
These functions have been created by scripts on the server and by dynamic HTML pages without having to resort to an exterior plug-in (which is a fixed constraint in our specifications). Figure 8.6 is a screenshot of a hypothetical work session dealing with Pascal’s Arithmetical Triangle. We can find a page from the CNUM catalog (a), as well as two windows (b) of which one has been reduced by the user. Another window corresponds to another of Pascal’s texts on the site of the ABU (c). The user also takes notes or extracts of text with his preferred software (d).
Figure 8.6. Print screen of a working session in progress with the CNUM and ABU websites
Despite these efforts it seems that the majority of users of digital libraries download their documents in order to print them. Letters from users of the CNUM have mentioned that the main problem they have is related to the downloading and
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printing of documents. In [CUB 98a] there is a comparative study for the site of the ABU which compares the downloading of documents to the reading of documents on their website. The report shows that on average the size of one download is equivalent to eight documents being read. The study “BibUsages” carried out on the Gallicia website has shown a more unfavorable result for the scanning through and reading of documents: for every 548 documents that were downloaded only 314 were read. Web interfaces have only experienced a limited amount of progress in comparison to FTP interfaces which were used previously.
Interfaces other than the Web are currently being used for the consultation of facsimiles of collections. The most widespread is Adobe Acrobat, but its use for large digitized collections with images remains difficult to master (navigating within illustrations is not very useful in this context, while researching occurrences of illustrations is also slow). Experimental systems have been developed in several laboratories: for example, BAMBI [CAL 98], Philectre [LEC 98] and DEBORA [DEB 02]. Like the Internet, all of these interfaces function based on the basic elements of the WIMP paradigm (Window, Icon, Menu, Pointer). The limits of this process arise in terms of the amount of space required on the computer screen, as can be seen in Figure 8.6. It would be difficult to add another window for supplementary text. Furthermore, even the organization of the window in itself involves a lot of work in terms of clicking, moving the windows and icons.
The effort forced on the user of such a system by reading on screen has been analyzed in [OHA 97] in comparison to traditional reading. This work has highlighted the need to have more fluid navigation techniques for reading interfaces as well as a larger flexibility in controlling the organization of documents on screen.
It seems that techniques such as those commonly used in computer-aided design can help resolve the issue. In bringing together the 3D geometric and visual characteristics of the documents and by inserting them into a common 3D scene, it then becomes possible to manipulate them.
In the reconstructed interface in Figure 8.7 the 3D scene is limited vertically by the floor. The camera is permanently fixed above this floor and its field is also fixed.
The facsimiles are presented in a specific tool in the shape of a tripod (similar to a simplified lectern). The book can be positioned arbitrarily on the floor, pushed back, pulled or pivoted by the user who can give their commands by selecting them on the green bar at the bottom of the tripod. This manipulation is carried out in real time with a simple pointing device similar to a mouse: two degrees of freedom are enough to determine the position of the tripod on the ground. Several tripods can also be positioned on the work screen. The movement of a tripod can be restricted due to the presence of other tripods or if there are any collisions between these 3D
3D Interaction for Digital Libraries 133 objects. The tripod can be removed by clicking on the green bar with a right-click of the mouse. It is possible to develop other interactive shortcuts to enable the user to move the tripod to the foreground of their computer screen. These shortcuts can also be found at the base of the tripod as buttons or menus.
Figure 8.7. The reading tripod
Scrolling through pages of the books is made possible by clicking on the page you are currently reading on the screen. Just like a traditional 2D window the tripod has a lift on its vertical axis in order to speed up the progression through the document (this is represented in Figure 8.7 as a ball). The horizontal axis enables the user to control the connection between the dimension (in pixels) of the facsimile and the chosen dimension of the tripod. There is also a zoom function which is independent of the positioning of the tripod that the user is working with. The size of the tripod can also be adjusted by using a specific handle (represented in Figure 8.7 by a ball at the top left of the tripod).
The thickness of the book should also be taken into account. The positioning of the book allows for easier localization of the selected page in the global text. The sections can be added as bookmarks corresponding to chapters or to passages selected by the user as in the 3Book system [CAR 04]. It is also possible to modify the appearance of the tripod in order to be able to display the open book. The action of page turning can be simulated by moving from one edge of the selected page to the other (Figure 8.8). A similar process (non-3D) had been suggested in the experiment known as “Turning the Page” carried out by the British Library [CAR 98]. This experiment is regularly used with great success in general public
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exhibitions of precious texts (for example, the exhibition of Leonardo da Vinci’s manuscripts at the Louvre). A more sophisticated animation based on the physical characteristics of a bent piece of paper has been described in [CHU 04, WIT 03].
The page-turning associated with a 3D representation of pages remains to be studied.
Figure 8.8. The tripod in page-turning mode
The proposed design for the lectern is clearly arbitrary. Due to the performance of the 3D structure we have limited the design to basic geometrics, and the analogy with a conventional window on a computer screen. The main advantage of the device (in comparison to those suggested in [CAR 04] and [CHU 04]) makes it possible to have a large number of lecterns within the same work session. The device also completes the lecterns by adding research and navigation tools to the collections of books.