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Life cycle of 3D data for Cultural Heritage

Bruno DUTAILLY | S. EUSÈBE | V. GRIMAUD | N. LEFÈVRE | M. QUANTIN | S. TOURNON VALIENTE | M. CHAYANI | X. GRANIER (Archéovision – 3D SHS Consortium, Bordeaux, France) Keywords: Archiving – 3D – Cultural Heritage- metadata Abstract: 3D is now commonly used for Cultural Heritage study, valorization and preservation. The gathered experiences make possible to define standard processes and practices to ensure data quality and their preservation. Under the supervision of the French national infrastructure for digital humanities (Huma-Num), the 3D Consortium has thus defined a life cycle of such data from creation up to archiving. It was part of its missions that are: bring together groups working in the field of archaeology and cultural heritage and with experience of using 3D technologies and producing 3D models; define the vocabulary associated with 3D technologies for HSS; develop specific open-source 3D tools; disseminate good practices and commissioning a conservatory dedicated to 3D data. We have formalized the different steps of data life Cycle. The first step consists in collecting data production from capture device (laser scanner, digital camera…). Such data which are denominated A0. The second step consists in processing the data (cleaning, meshing,…) to create the initial models V0. Finally, new modeling may be added to add new hypotheses for the restitution. This step may be iterated creating V1n versions up to the V2 that is the final version. A supplementary step may be added when valorization is considered. All versions from A0, V0 up to V2 are candidates for archiving. We have formalized this process with a sequential graph that introduces a metadata new schema dedicated to the long-term archiving of 3D models for HSS. We have also created a software aLTAG 3D, that leverage the usual complexity of documentation to create metadata and of checking that the 3D files are suitable for archiving. It creates an archive that can be pushed to the CINES – the French national infrastructure for high-performance computer, and for long-term digital...

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Elastic Flattening of Painted Pottery Surfaces

Reinhold PREINER | Stephan KARL | Paul BAYER | Tobias SCHRECK Generating flat images from paintings on curved surfaces is an important task in Archaeological analysis of ancient pottery. It allows comparing styles and painting techniques, e.g, for style and workshop attribution, and serves as basis for domain publications which typically use 2d images. To obtain such flat images from scanned textured 3d models of the pottery objects, current practice is to perform so-called rollouts using approximating shape primitives like cones or spheres, onto which the mesh surfaces are projected. While this process provides in intuitive deformation metaphor for the users, it naturally introduces unwanted distortions in the mapping of the surface, especially for vessels with high-curvature profiles. In this work, we perform an elastic flattening of these projected meshes, where stretch energy is minimized by simulating a physical relaxation process on a damped elastic spring model. We propose an intuitive contraction-directed physical setup which allows for an efficient relaxation while ensuring a controlled convergence. Our work has shown to produce images of significantly improved suitability for domain experts’ tasks like interpretation, documentation and attribution of ancient...

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Gloss Characterization and Calibration for Material Appearance Reproduction of Paintings

Willemijn ELKHUIZEN | Tessa ESSERS | Yu SONG | Jo GERAEDTS | Sylvia PONT | Joris DIK Being able to link captured material characteristics and fabricable material appearance attributes is important for creating life-like reproductions. In this paper we propose a method for gloss calibration, and an approach for gloss gamut mapping, as part of an integrated approach for color, topography and gloss reproduction. For gloss calibration, gloss calibration targets were printed in the primary printing colors (CMYK and White), with uniform gloss in equal distant gloss levels. These targets were scanned using the proposed gloss scanner. To create the gloss gamut map, a monotonic curve was fitted to the mean gloss scan values at different gloss levels. Analysis of fitted curves indicated that the gloss mapping is independent of the diffuse colors. As a case study, the painting ‘Fruit Still Life’ by C. de Heem was scanned, and the measured gloss was mapped to printable gloss levels using the relation described by the fitted curve. The printed result shows good correspondence to the painting’s appearance, with clearly distinguishable gloss features for the in-gamut glass...

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Material Aging Visualization for Cultural Heritage Artifacts

Adamopoulos GEORGIOS | Anastasia MOUTAFIDOU | Anastasios DROSOU | Dimitrios TZOVARAS | Ioannis FUDOS Material aging has a significant effect on the appearance of cultural heritage objects. These aging effects depend on material composition, object usage and weathering conditions but also on physical and chemical substance parameters. Some types of changes in the materials underneath the visible layers can also be detected and subsequently simulated. Furthermore, recent 3D printing technology enables exporting 3D objects with transparency information. We report on the development of software tools for analysis, emulation, and visualization of material aging for artwork objects that can be used by curators and archaeologists to understand the nature of aging and prevent it with minimal preservation...

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Aging Prediction of Cultural Heritage Samples Based on Surface Microgeometry

Irina Mihaela CIORTAN | G. MARCHIORO | C. DAFFARA | Ruggero PINTUS | Enrico GOBBETTI | Andrea GIACHETTI A critical and challenging aspect for the study of Cultural Heritage (CH) assets is related to the characterization of the materials that compose them and to the variation of these materials with time. In this paper, we exploit a realistic dataset of artificially aged metallic samples treated with different coatings commonly used for artworks’ protection in order to evaluate different approaches to extract material features from high-resolution depth maps. In particular, we estimated, on microprofilometric surface acquisitions of the samples, performed at different aging steps, standard roughness descriptors used in materials science as well as classical and recent image texture descriptors. We analyzed the ability of the features to discriminate different aging steps and performed supervised classification tests showing the feasibility of a texture-based aging analysis and the effectiveness of coatings in reducing the surfaces’ change with...

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