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Digital Reconstruction and 4D Presentation through Time
El-Hakim, Sabry; Lapointe, Jean-François; Whiting, E.
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National Research Council Canada Institute for Information Technology Conseil national de recherches Canada Institut de technologie de l'information
Digital Reconstruction and 4D Presentation
through Time *
El-Hakim, S.F., Lapointe, J., Whiting, E.
August 2008
* Proceedings of the International Conference on Computer Graphics
and Interactive Techniques, SIGGRAPH 2008, Los Angeles,
California, August 11–15, 2008.
Copyright 2008 by
National Research Council of Canada
Permission is granted to quote short excerpts and to reproduce figures and tables from this report, provided that the source of such material is fully acknowledged.
Copyright is held by the author / owner(s).
SIGGRAPH 2008, Los Angeles, California, August 11–15, 2008. ISBN 978-1-60558-466-9/08/0008
Digital Reconstruction and 4D Presentation through Time
Sabry F. El-Hakim∗Visual Information Technology National Research Council Canada
Jean-Franc¸ois Lapointe†
Visual Information Technology National Research Council Canada
Emily Whiting‡
Department of Architecture MIT
Figure 1: The 4D interactive presentation, with time slider, in the Demotride viewer.
1
Introduction
Virtual time travel transforming the existing remains of a heritage site to its original condition has value for education and cultural understanding. However, digitally reconstructing objects which no longer exist is a challenge. Interaction and navigation within virtual 4D worlds (adding time to 3D worlds) is also problematic due to imprecise understanding of the time dimension. In this project we developed an approach to 3D modeling of sites that have undergone changes over the years. The method creates independent models from different types of data, such as frescoes, paintings, drawings, old photos, historic documents, and digitized remains. The models are assembled and integrated for a 4D interactive presentation. Several research issues have been addressed: (1) Modeling from frescoes and drawings with incorrect perspective, (2) modeling from paintings and old photos including fine geometric details from shading (3) coloring models from old photos and drawings to match existing elements, (4) creation of models by seamless and accurate integration of data obtained from independent sources, and (5) the creation of intuitive interactive presentations that link the models with other multimedia components and information related to the history of the site. We will describe contributions to these issues, including our own advanced model viewer [Dem ], and apply them to modeling heritage sites such as Venice which appeared in paintings by Canaletto, Bernardo Bellotto, and Francesco Guardi, and many 19th century photos. Canalettos paintings have been used to measure the subsidence of Venice [Camuffo and Sturaro 2003].
2
Approach
Techniques to create models from frescoes, paintings, and old photos have been developed. For old frescoes or paintings with incorrect perspective, the method requires that part of the object or site still exists, for example, its foundation or archaeological remains. We use measurements from those remains to resample the source material, create an image with correct perspective, and use this to reconstruct the site. For Renaissance paintings, which have correct perspective, and old photos, we use our flexible approach for 3D construction from single images [El-Hakim 2001].
∗e-mail:Sabry.El-Hakim@nrc-cnrc.gc.ca †e-mail:Jean-Francois.Lapointe@nrc-cnrc.gc.ca ‡e-mail:ewhiting@csail.mit.edu
The approach applies several constraints: coordinate constraints, surface constraints, and topological constraints in two steps: a calibration step and a reconstruction step. The solution is based on Photogrammetric principles.
It is challenging to develop effective tools for visualizing virtual sites in 4 dimensions, for use by experts and non-experts. There is no standard approach for interacting with the time dimension, especially with models of sites that have changed over time. Many approaches have been tried, however the outcome is usually only a pre-rendered movie, which bypasses the interactivity problems. We developed the Demotride viewer, which works with content based on VRML and X3D. Specifically, Demotride’s support of time sensors allows animation of time and interaction with the 4D models. One feature that distinguishes Demotride from other viewers is its ability to provide what we call controlled inter-action, where the user is bound to respect the visualization and interaction parameters specified by the content developer. For example, Demotride supports unique features that permit control of the walkthrough parameters (orientation speed and interaction technique) when navigating in the virtual scene.
The approach has been applied to Venice sites, such as Piazza San Marco and the Arsenale (figure 1), and other cities in Italy (Florence, Padua, Trento) and Canada. Since we are still refining the procedure, future work includes comprehensive evaluation of the interactive presentation alternatives, at various configurations, by several groups of users. Both experienced and non-experienced users will be drawn upon. Further work involves designing and implementing an immersive system.
References
CAMUFFO, D., ANDSTURARO, G. 2003. Sixty-cm submersion
of Venice discovered thanks to Canaletto’s paintings. Climate
Change 58, 333–343.
Demotride Viewer. http://www.demotride.net.
EL-HAKIM, S. F., 2001. A flexible approach to 3D reconstruction
from single images. ACM SIGGRAPH’01 Technical Sketches. SIDERIS, A., AND ROUSSOU, M. 2002. Making a new world
out of an old one: In search of a common language for archaeological immersive VR representation. VSMM, 31–42.
