3D Reconstruction applied to Virtual Heritage and Cultural Conservation
Joao G.M. Goncalves , European Commission, Italy
Vitor Sequeira , European Commission, Italy
http://www.jrc.cec.eu.int

Short Paper: Short Paper 1: Restoration and Preservation

The objective of 3D Reconstruction is to create a 3D photo-realistic computer model of a real object, building or monument, both indoors and outdoors. Our approach to 3D Reconstruction is to combine distance measurements and pictures. Two technologies are used: i) a combined laser - digital camera sensor for data acquisition and ii) mobility for resolving spatial occlusions. After a few scanning operations from different capture points, it is possible to create complete 3D triangulated models of a particular building/monument "as-built". The acquired 3D points are first triangulated and each triangle is then textured (i.e., painted) with the correct colours taken from the acquired photographs. The final 3D models have the following characteristics:

• Internet compatible - models are coded into VRML (Virtual Reality Modelling Language) and can thus be viewed with any major Internet browser irrespectively of the computing platform or operating system;
• Visually appealing - This derives from the fact that the models are textured with the visual information coming from real scene photos;
• Geometrically and dimensionally accurate - Existing laser scanners acquire 3D points with an accuracy of around 1cm over a distance of more than 100m;
• Model size adapted to application - It is thus possible to adapt the model size to existing transmission or storage requirements by decimating the 3D-triangle mesh and/or re-coding the photographic images;
• Provide a realistic feeling of "being of there" - It is possible to navigate interactively through or around the model and perceive the existing spatial relationships, as if one is exploring the real environment;
• Framework for advanced Human Computer Interface - It is possible to create dedicated hyperlinks to any type of multimedia material, enabling more "natural" navigation due to the spatial context provided;
• Multiple Level of Detail - It is possible to insert or integrate previously acquired detailed models into the overall model (e.g., a highly detailed model of a small artistic craft can be inserted inside the model of a room), allowing therefore the easy creation of virtual and dynamic exhibition spaces or museums;
• Application specific tools and interfaces - Java scripts/applets can be easily written for specific tasks (e.g., measurement of the real dimensions, surfaces or volumes), or for more easy navigation.

The paper addresses the main steps in building a complete 3D texture-mapped model and presents the results of some projects involving the 3D modelling of Heritage Buildings, in particular state-of-the-art models of the "Cour d'Honneur" and "Salon Delacroix" at the French National Assembly (Palais Bourbon), Paris, as well as the "Sala dello Scrutinio" at the Doges' Palace, Venice.

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