Escaneado de artefactos religiosos con un escáner de luz estructurada

[EN] The digitization process for religious artifacts is subject to inherent difficulties often ignored in theoretical models or pipelines. In this paper we aim to describe these problems, which are present in practical environments such as temples and churches, using white light scanners instead of other common devices or technologies such as laser scanners and photogrammetry. Our case study is based on the digitization of two religious statues belonging to a Catholic brotherhood located in a village of the Province of Jaén (Spain), one of them presenting especially several limitations. After performing the scanning process with a portable hand-held scanner, the images captured were processed until the final models were acquired. On the basis of the results obtained, we discuss the problems arising after using well-known procedures for the reconstruction of 3D models, their causes and some possible solutions to achieving a correct digitization. It should be noted that it is not the aim of this study to establish procedures for the digitization of religious artifacts, but rather to transmit the inherent constraints of these types of scenes.[ES] Los modelos teóricos de digitalización 3D no tienen en cuenta problemas de escenarios específicos como el de la digitalización de objetos religiosos. El objetivo de este artículo es describir estos problemas presentes en entornos prácticos como templos o iglesias usando un escáner de luz blanca en lugar de otros instrumentos o tecnologías comunes como los escáneres láser y la fotogrametría. Nuestro caso de estudio se basa en la digitalización de dos tallas religiosas pertenecientes a una cofradía de una localidad de la provincia de Jaén (España), siendo especialmente restrictiva una de ellas. Tras el procedimiento de escaneado llevado a cabo con un escáner de mano, las capturas se procesaron usando procedimientos clásicos de reconstrucción de modelos 3D hasta obtener los resultados finales. Basándonos en los resultados obtenidos realizamos una discusión de los problemas, causas y posibles soluciones para llevar a cabo una correcta digitalización. Cabe destacar que el objetivo del artículo más que establecer un flujo de trabajo es el de presentar las restricciones que presentan este tipo de entornos.This study has been partially supported by the Ministerio de Ciencia e Innovación and the European Union (via ERDF funds) under the research project TIN2014-58218-R, and by the University of Jaén through the research project UJA2015/08/10Graciano, A.; Ortega, L.; Segura, RJ.; Feito, FR. (2017). Digitization of religious artifacts with a structured light scanner. Virtual Archaeology Review. 8(17):49-55. doi:10.4995/var.2016.4650SWORD4955817Wang, K., Lavoué, G., Denis, F., & Baskurt, A. (2011). Robust and blind mesh watermarking based on volume moments. Computers & Graphics, 35(1), 1-19. doi:10.1016/j.cag.2010.09.01

Making 3D implants for conservation and restoration of archaeological glass

[EN] This article describes the restoration of a glass bowl from the 16th-17thcentury by creating its three-dimensional (3D)model. The final purpose is to work with this model in order to avoid damaging situations that are associated with the manipulation of fragile objects. The gap areas, those corresponding to the missing fragments not found in the excavation, were carried out by constructing digital implants. A restricted area of the 3D model has been duplicated in order to accommodate it to confined intervals of the gap. The final implants were printed with acrylonitrile butadiene styrene (ABS) filament. These implants replace the lost areas and give stability back to the item by recovering the original morphology. The result can be compared with the outcome obtained by a traditional process, but differs due to the fact that requires minimum manipulation of the item, so it can contribute to preserve and safeguard the restored object. This is a non-invasive method which is offered as an alternative treatment, where the archaeological object is replaced by its virtual model in the steps of the process after 3D data acquisition. Significant differences have not been found in the 3D printing results obtained with the two types of filaments tested (white and clear).[ES] En este artículo se restaura un cuenco de vidrio del siglo XVI-XVII mediante la creación de su modelo tridimensional (3D)con el fin de operar con él y eliminar el riesgo que entraña la manipulación de objetos frágiles. La áreas faltantes, correspondientes a los fragmentos de vidrio no encontrados en la excavación, se han llevado a cabo mediante la construcción digital de implantes. Para elaborar los implantes se ha duplicado un volumen del modelo 3D del cuenco adaptándolo al espacio confinado en las áreas vacías. La impresión de los implantes se ha hecho con filamento acrilonitrilo butadieno estireno(ABS). Estos implantes, que sustituyen a las zonas perdidas, han devuelto la estabilidad a la pieza y han permitido recrear la morfología original. El resultado puede ser comparado al obtenido por métodos tradicionales,pero difiere en que requiereuna mínimamanipulación del objeto, contribuyendo así, a la preservación y salvaguarda del objeto restaurado. Este método no invasivo se ofrece como un tratamiento alternativo,donde el objeto arqueológico es sustituido por su modelo virtual en todas las fases del procesoposteriores a la captura de datos 3D. No se han encontrado diferencias significativas en cuanto a los resultados obtenidos de impresión 3D con los dos tipos de filamentos ensayados(blanco y translúcido).El trabajo se ha desarrollado gracias al Programa del Plan Nacional de I+D+i 2008-2011 del Ministerio de Economía y Competitividad de España, Proyectos HAR2012-38391-C02-01 y HAR2012-38391-C02-02. También se ha desarrollado a través del Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad en el marco del Plan Estatal de Investigación Científica y Técnica y de Innovación 2013-2016 del Ministerio de Economía y Competitividad de España con cofinanciación del Fondo Europeo de Desarrollo Regional (FEDER), Proyecto HAR2015-69408-R (MINECO/FEDER). Los autores quieren agradecer la colaboración del Museo de Cerámica de Manises y especialmente a su directora Dña. Sara Blanes Ibáñez, por proporcionar la pieza usada para ilustrar la técnica propuestaDíaz-Marín, C.; Aura-Castro, E. (2017). Creación de implantes 3D en procesos de conservación y restauración de vidrio arqueológico. Virtual Archaeology Review. 8(16):103-109. https://doi.org/10.4995/var.2017.5946SWORD10310981

Digitization of religious artifacts with a structured light scanner

The digitization process for religious artifacts is subject to inherent difficulties often ignored in theoretical models or pipelines. In this paper we aim to describe these problems, which are present in practical environments such as temples and churches, using white light scanners instead of other common devices or technologies such as laser scanners and photogrammetry. Our case study is based on the digitization of two religious statues belonging to a Catholic brotherhood located in a village of the Province of Jaén (Spain), one of them presenting especially several limitations. After performing the scanning process with a portable hand-held scanner, the images captured were processed until the final models were acquired. On the basis of the results obtained, we discuss the problems arising after using well-known procedures for the reconstruction of 3D models, their causes and some possible solutions to achieving a correct digitization. It should be noted that it is not the aim of this study to establish procedures for the digitization of religious artifacts, but rather to transmit the inherent constraints of these types of scenes

Virtual 3D Reconstruction of Archaeological Pottery Using Coarse Registration

The 3D reconstruction of objects has not only improved visualisation of digitised objects, it has helped researchers to actively carry out archaeological pottery. Reconstructing pottery is significant in archaeology but is challenging task among practitioners. For one, excavated potteries are hardly complete to provide exhaustive and useful information, hence archaeologists attempt to reconstruct them with available tools and methods. It is also challenging to apply existing reconstruction approaches in archaeological documentation. This limitation makes it difficult to carry out studies within a reasonable time. Hence, interest has shifted to developing new ways of reconstructing archaeological artefacts with new techniques and algorithms. Therefore, this study focuses on providing interventions that will ease the challenges encountered in reconstructing archaeological pottery. It applies a data acquisition approach that uses a 3D laser scanner to acquire point cloud data that clearly show the geometric and radiometric properties of the object’s surface. The acquired data is processed to remove noise and outliers before undergoing a coarse-to-fine registration strategy which involves detecting and extracting keypoints from the point clouds and estimating descriptions with them. Additionally, correspondences are estimated between point pairs, leading to a pairwise and global registration of the acquired point clouds. The peculiarity of the approach of this thesis is in its flexibility due to the peculiar nature of the data acquired. This improves the efficiency, robustness and accuracy of the approach. The approach and findings show that the use of real 3D dataset can attain good results when used with right tools. High resolution lenses and accurate calibration help to give accurate results. While the registration accuracy attained in the study lies between 0.08 and 0.14 mean squared error for the data used, further studies will validate this result. The results obtained are nonetheless useful for further studies in 3D pottery reassembly

Virtual reconstruction and representation of an archaeological terracotta statue

This paper describes the virtual reconstruction of a late fifteenth century terracotta statue. The proposed solution was adopted during the restoration process when it was not possible to get back the fragments from the missing parts that were lost during the burial period. The archaeological statue that has been called 'Crist del Fossar', according to its morphology and provenance, was found severely damaged, as it appeared highly fragmented with dull and age-worn edges. The restoration was assisted by means of an automatic reassembly technique that operates on digital models of fragments. This technique considers the best alignments between themselves (without the need to manipulate the original ones) and leads the reassembly and adhesion processes of the fragments. The statue will be part of a temporary exhibition at the Museu de Prehistòria de València where visitors would be able to appreciate the restoration of the few fragments that have been conserved and will be able to explore the virtual reconstruction of the entire statue through an immersive 3D interactive visualization