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Subject: Categories and Subject Descriptors (according to ACM CCS): I.3.3 [Computer Graphics]: Picture/Image Generation-Digitizing and scanning × Has files: true × Start date: 2010 × End date: 2011 ×

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Now showing 1 - 5 of 5
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    Radiometric Characterization of Spectral Imaging for Textual Pigment Identification
    (The Eurographics Association, 2011) Kim, Min H.; Rushmeier, Holly; Franco Niccolucci and Matteo Dellepiane and Sebastian Pena Serna and Holly Rushmeier and Luc Van Gool
    Digital imaging of cultural heritage artifacts has become a standard practice. Typically, standard commercial cameras, often commodity rather than scientific grade cameras, are used for this purpose. Commercial cameras are optimized for plausible visual reproduction of a physical scene with respect to trichromatic human vision. However, visual reproduction is just one application of digital images in heritage. In this paper, we discuss the selection and characterization of an alternative imaging system that can be used for the physical analysis of artifacts as well as visually reproducing their appearance. The hardware and method we describe offers a middle ground between the low cost and ease of commodity cameras and the high cost and complexity of hyperspectral imaging systems. We describe the selection of a system, a protocol for characterizing the system and provide a case study using the system in the physical analysis of a medieval manuscript.
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    Images from Self-Occlusion
    (The Eurographics Association, 2011) Alexa, Marc; Matusik, Wojciech; Douglas Cunningham and Tobias Isenberg
    We propose a complete system for designing, simulating, and fabricating surfaces with shading due to selfocclusion that induce desired input images. Our work is based on a simple observation. Consider a cylindrical hole (a pit) in a planar surface. As the depth of the hole increases, the radiance emitted from the surface patch that contains the hole decreases. This is because more light is trapped and absorbed in the hole. First, we propose a measurement-based approach that derives a mapping between average albedo of the surface patch containing the hole and the hole depth. Given this mapping and an input image, we show how to produce a distribution of holes with varied depth that approximates the image well. We demonstrate that by aligning holes with image features we can obtain reproductions that look better than those resulting from regular hole patterns despite using slightly less holes. We validate this method on a variety of images and corresponding surfaces fabricated with a computer-controlled milling machine and a 3D printer.
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    Improving High-Speed Scanning Systems by Photometric Stereo
    (The Eurographics Association, 2011) Larue, Frédéric; Dellepiane, Matteo; Scopigno, Roberto; Franco Niccolucci and Matteo Dellepiane and Sebastian Pena Serna and Holly Rushmeier and Luc Van Gool
    High-speed scanning systems can be extremely valuable for Cultural Heritage applications, especially when large collections of small objects have to be acquired. However, fine details may not be acquired using this technology. Nevertheless, it is possible to try to recover them by taking advantage of the additional data provided by these systems: the calibrated video sequence of the acquisition, and the position of the projector light for each frame. In this paper, we propose a workflow that processes the video sequence with a photometric stereo approach, in order to refine the coarse geometry provided by the scanner. A normal map is first extracted by a method that accounts for the unevenly distributed sampling that generally results from the particular trajectory followed by this kind of scanners during the acquisition. This normal map is then integrated in order to recover missing geometric features. Good performances are achieved, since the whole workflow is particularly suited to GPU programming.
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    Verification and Acceptance Tests for High Definition 3D Surface Scanners
    (The Eurographics Association, 2010) Bathow, Christiane; Breuckmann, Bernd; Scopigno, Roberto; Alessandro Artusi and Morwena Joly and Genevieve Lucet and Denis Pitzalis and Alejandro Ribes
    High definition three-dimensional (3D) surface scanners, based on structured light or laser light section techniques, have found a wide range of applications, especially for technical and industrial applications (mostly for measuring and inspection tasks). Since about 10 years, systems adapted for the requirements of arts and Cultural Heritage (CH) support 3D digitization of art objects. Although the use of digital 3D models in CH is rapidly growing, many of the users are not yet completely familiar with terminology and all details of technical specifications. As most of the users are practitioners there is sometimes only little experience with terms as data quality, accuracy, resolution, measurement uncertainty, especially because these terms are used in very different ways, in manuals and brochures of scanner manufacturers as well as by authors of scientific papers. Moreover, the objective of many applications is digitization instead of measurement; therefore, many users are not even aware, that they nevertheless have to care about metrology issues such as verification and acceptance tests of the used equipment to get a reliable scanning result. In its first part, the paper will give an overview the fundamentals of data acquisition and data processing, presenting also advantages and benefits, limitations and drawbacks as well as correlations between different performance parameters of high definition 3D surface scanners. Our goal is also to rectify a number of typical misunderstandings and to clarify related terms and definitions. In its second part, the paper will concentrate on verification and acceptance tests of high definition 3D scanners, reviewing the German guidelines VDI/VDE 2634/2 and proposing some preliminary extensions required to cope better with the CH domain.
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    Virtual Replication of the Idalion Tablet
    (The Eurographics Association, 2010) Robin, Bertille; Hilpert, Thibaut; Miyazawa, Keisuke; Callet, Patrick; Contencin, François-Xavier de; Zymla, Anna; Alessandro Artusi and Morwena Joly and Genevieve Lucet and Denis Pitzalis and Alejandro Ribes
    The Idalion Tablet is an antique bronze (480-470 BC) found around 1850 in the antique city of Idalion in Cyprus. It has an important historical value for Cyprus, as it is the longest testimony of Cyprus sillabary writing. The tablet has been the property of the Bibliothèque Nationale de France (BNF) since 1862. Our final goal is to realise a per- fect physical copy of the Idalion Tablet (scale 1, with no patina) as a donation to the Idalion Museum in Cyprus. In a few months the historical building "Richelieu" of the Bibliothèque Nationale de France is going to be renovated, leading the museum to close for an unknown time. We present here the realisation of a high quality virtual copy of the Idalion tablet, with the same shape and a spectrally simulated visual appearance of the precious artefact as it could be in the ancient times. We used 3D digitization to create a virtual and accurate replica of the tablet shape as we were not allowed to handle it directly. The Centre de Recherche et de Restauration des Musées de France (C2RMF) took a sample of the alloy out of the Idalion Tablet, and analysed its elementary composition using the PIXE method. The complex index of refraction of the alloy was calculated using previous scientific results. The virtual copy was then computed with the Virtuelium free software. The physically based images obtained by spec- tral simulation will be used on the BNF website to give the public an access to its collections. A didactic movie is also in progress for that purpose. We shall then realise the physical copy of the tablet by rapid prototyping, and casting, in collaboration with the Centre Technique des Industries de la Fonderie (CTIF) and the Ecole Supérieure de Fonderie et de Forge (ESFF).