Search Results (12)

In the digital 3D reconstruction of the shapes and surface reflectance of ancient paintings and drawings using Photometric Stereo (PS) techniques, normal integration is a key step. However, difficulties in locating light sources, non-Lambertian surfaces, and shadows make the results of this step inaccurate for such artworks. This paper presents a solution for PS to overcome this problem based on some enhancement of the normal integration process and the accurate measurement of Points of Interest (PoIs). The mutual positions of the LED lights, the camera sensor, and the acquisition plane in two custom-designed stands, are measured in laboratory as a system calibration of the 3D acquisition workflow. After an introduction to the requirements and critical issues arising from the practical application of PS techniques to artworks, and a description of the newly developed PS solution, the measurement process is explained in detail. Finally, results are presented showing how the normal maps and 3D meshes generated using the measured PoIs’ positions, and further minimized using image processing techniques, which significantly limits outliers and improves the visual fidelity of digitized artworks. Full article

This study focuses on slope stability and geological hazard analyses at the Italian Paleolithic site of Grotta Paglicci. The site is characterized by a cave that contains rich archaeological and anthropological finds, spanning various Paleolithic periods, and includes faunal remains, lithic artifacts, human burials, ornaments, mobiliary art objects, and unique Paleolithic wall paintings. The study employs a multi-technique approach that includes topographic surveys carried out by the robotic total station and GNSS receivers, photogrammetric acquisitions with an unmanned aerial system, 3D SLAM-based LiDAR mapping, and an engineering geological survey. The collected data allowed for the creation of georeferenced 3D models that were utilized in rock slope stability analysis and modeling. The results of this comprehensive survey highlighted how the bedding and joint discontinuities influence rock stability in both the external and internal areas of the cave. The integrated use of SLAM-based LiDAR and photogrammetry has been proven to be an efficient and essential tool in the evaluation of the structural interactions between the external morphology and the cave, thus allowing the proposal of safety measures that will keep the site accessible for future activities. Full article

The 3D digital reproduction of panel paintings is an efficient practice through which to document their state of conservation thanks to the ability to study artwork both at the microscopic level, visualising the craquelure and the detachments of pictorial layers, and at the macroscopic level, analysing support structures and their deformations. In recent years, research has focused on new methodologies to handle multiple 3D scans acquired over time and to achieve data fusion to obtain multi-resolution products. In this paper, we present the results of the acquisition of the central panel of an earthquake-damaged triptych using two different 3D techniques (close-range photogrammetry and structured light) before and after its restoration to carry out a multi-temporal analysis of the conservation status and document the effects of the restoration. Furthermore, we performed laser scanning micro-profilometry on a small area of the painting to study the artist’s technique and identify previous restorations. Finally, we merged the two 3D datasets (obtained by structured-light projection and micro-profilometry) to produce a multi-resolution 3D model with the aim of increasing the accuracy and readability of the final product. Full article

Estimating depth from images is a common technique in 3D perception. However, dealing with non-Lambertian materials, e.g., transparent or specular, is still nowadays an open challenge. However, to overcome this challenge with deep stereo matching networks or monocular depth estimation, data sets with non-Lambertian objects are mandatory. Currently, only few real-world data sets are available. This is due to the high effort and time-consuming process of generating these data sets with ground truth. Currently, transparent objects must be prepared, e.g., painted or powdered, or an opaque twin of the non-Lambertian object is needed. This makes data acquisition very time consuming and elaborate. We present a new measurement principle for how to generate a real data set of transparent and specular surfaces without object preparation techniques, which greatly reduces the effort and time required for data collection. For this purpose, we use a thermal 3D sensor as a reference system, which allows the 3D detection of transparent and reflective surfaces without object preparation. In addition, we publish the first-ever real stereo data set, called TranSpec3D, where ground truth disparities without object preparation were generated using this measurement principle. The data set contains 110 objects and consists of 148 scenes, each taken in different lighting environments, which increases the size of the data set and creates different reflections on the surface. We also show the advantages and disadvantages of our measurement principle and data set compared to the Booster data set (generated with object preparation), as well as the current limitations of our novel method. Full article

In the field of the Cultural Heritage (CH), image-based 2D and 3D digital acquisition is today the most common technique used to create digital replicas of existing artifacts. This is carried out for many reasons, such as the following: research, analysis, preservation, conservation, communication, and valorization. These activities usually require complementary specialized equipment, tailored to specific purposes in order to achieve the desired results. This equipment is not easy-to-find on the market, it is not always affordable for museums operators; it is sometimes expensive, and it usually needs tricky customizations. However, the development in recent years of more generalized, versatile, and affordable instruments and technologies has led to new approaches, leveraging a new generation of low-cost, adaptable equipment. This paper presents custom-made equipment following this new path, designed to provide optimized results through calibrated tools alongside the software to make it work. The essay focuses specifically on the self-production of instruments for the digital reproduction of ancient drawings, manuscripts, paintings, and other museum artifacts and their transformative impact on digitization techniques. The outcomes of self and custom-built equipment specifically produced for the contexts described in this paper highlight their potential to foster interdisciplinary collaboration, facilitate scholarly research, enhance conservation efforts, and promote cultural exchange. The final goal is to propose inexpensive equipment that is easy to use (even by not specifically trained operators) and that provides remarkable quality. Full article

GPR (Ground Penetrating Radar) is a technology widely applied today in the field of non-destructive investigations. From its first applications, the field of use has involved environmental and archaeological contexts and, only recently, non-destructive investigations for the diagnostics of existing buildings, including historical ones. In the latter, the GPR is, in particular, addressed to the NDT diagnostics of walls, which often support paintings of considerable value. In this study, GPR technology was used to investigate the walls of the Bardi Chapel in the Santa Croce Basilica in Florence, which features Giotto’s frescoes. The GPR acquisition was performed with a three-antenna module that, through multiple scans, allowed to reconstruct the full 3D tomography of the three main walls of the chapel. The development of a customized system made it possible to extend the investigation area to almost the entire wall and to avoid contact between the instrument and the wall paint, thus safeguarding its integrity. The collected data, once inserted in a unified framework of the HBIM model, geo-referenced, and equipped with the information content, allowed us to evaluate the masonry structure and to generate masonry data for subsequent seismic vulnerability assessments. Full article

An algorithm for automatically planning trajectories designed for painting large objects is proposed in this paper to eliminate the difficulty of painting large objects and ensure their surface quality. The algorithm was divided into three phases, comprising the target point acquisition phase, the trajectory planning phase, and the UR5 robot inverse solution acquisition phase. In the target point acquisition phase, the standard triangle language (STL) file, algorithm of principal component analyses (PCA), and k-dimensional tree (k-d tree) were employed to obtain the point cloud model of the car roof to be painted. Simultaneously, the point cloud data were compressed as per the requirements of the painting process. In the trajectory planning phase, combined with the maximum operating space of the UR5 robot, the painting trajectory of the target points was converted into multiple traveling salesman problem (TSP) models, and each TSP model was created with a genetic algorithm (GA). In the last phase, in conformity with the singularities of the UR5 robot’s motion space, the painting trajectory was divided into a recommended area trajectory and a non-recommended area trajectory and created by the analytical method and sequential quadratic programming (SQP). Finally, the proposed algorithm for painting large objects was deployed in a simulation experiment. Simulation results showed that the accuracy of the algorithm could meet the requirements of painting technology, and it has promising engineering practicability. Full article

The European Synchrotron Radiation Facility (ESRF) has recently commissioned the new Extremely Brilliant Source (EBS). The gain in brightness as well as the continuous development of beamline instruments boosts the beamline performances, in particular in terms of accelerated data acquisition. This has motivated the development of new access modes as an alternative to standard proposals for access to beamtime, in particular via the “block allocation group” (BAG) mode. Here, we present the recently implemented “historical materials BAG”: a community proposal giving to 10 European institutes the opportunity for guaranteed beamtime at two X-ray powder diffraction (XRPD) beamlines—ID13, for 2D high lateral resolution XRPD mapping, and ID22 for high angular resolution XRPD bulk analyses—with a particular focus on applications to cultural heritage. The capabilities offered by these instruments, the specific hardware and software developments to facilitate and speed-up data acquisition and data processing are detailed, and the first results from this new access are illustrated with recent applications to pigments, paintings, ceramics and wood. Full article

The experience of an object derives not only from the sight but also from the touch: a tactile exploration can reveal the smallest information trapped within the surface up to our tactile detective threshold. Starting from the importance of this observation in the case of works of art, this research demonstrates the use of conoscopic holography sensors for high-quality acquisition of the surface of artworks (up to the micro-scale) suitable also to 3D printing. The purpose is twofold, allowing for the tactile use of the artwork, which is otherwise impossible, for visually impaired people and for new use in regard to scientific information purposes. In detail, the workflow to obtain a 3D printed replica of multiscale and polychrome artworks suitable for the haptic fruition is validated, but the potential of the tool as an innovative resource for scientific visualization of the microsurface of the artwork for conservation issues is also demonstrated. The validation was performed on notable Italian masterpieces, such as Donatello’s “Death Cristh” bronze relief in Padua and the Tintoretto painting “St. Martial in Glory with the Saints Peter and Paul” in Venice. Full article

We discuss a synchronised sensing technique for the analysis of painted surfaces of frescos. Specifically, the performance of Visible-Near Infrared (VIS-NIR) Reflectance Imaging Spectroscopy (RIS) synchronized with three-dimensional (3D) acquisition is demonstrated in the study of a detached mural painting by Alessandro Botticelli. Synchronized sensing generates georeferenced data for simplified data treatment and interpretation. We show how such output data can provide key information to interpret important fresco surface and subsurface features (e.g., painting technique, material composition, pentimenti). Full article

Among the possible variants of X-Ray Fluorescence (XRF), applications exploiting scanning Macro-XRF (MA-XRF) are lately widespread as they allow the visualization of the element distribution maintaining a non-destructive approach. The surface is scanned with a focused or collimated X-ray beam of millimeters or less: analyzing the emitted fluorescence radiation, also elements present below the surface contribute to the elemental distribution image obtained, due to the penetrative nature of X-rays. The importance of this method in the investigation of historical paintings is so obvious—as the elemental distribution obtained can reveal hidden sub-surface layers, including changes made by the artist, or restorations, without any damage to the object—that recently specific international conferences have been held. The present paper summarizes the advantages and limitations of using MA-XRF considering it as an imaging technique, in synergy with other hyperspectral methods, or combining it with spot investigations. The most recent applications in the cultural Heritage field are taken into account, demonstrating how obtained 2D-XRF maps can be of great help in the diagnostic applied on Cultural Heritage materials. Moreover, a pioneering analysis protocol based on the Spectral Angle Mapper (SAM) algorithm is presented, unifying the MA-XRF standard approach with punctual XRF, exploiting information from the mapped area as a database to extend the comprehension to data outside the scanned region, and working independently from the acquisition set-up. Experimental application on some reference pigment layers and a painting by Giotto are presented as validation of the proposed method. Full article

The aim of this work is to present a new practical approach to digital photogrammetry to obtain 3D models of polychromatic sculptures under ultraviolet fluorescence and near-infrared by starting from photographic images. This digital photogrammetry was applied recently to a 17th-century reliquary bust representing St. Rodonio, a saint particularly venerated by the Orthodox Church, presently under restoration in the Laboratories of University of Tuscia and belonging to the Museum of Colle del Duomo of Viterbo (Italy). The acquisitions of ultraviolet fluorescence and infrared frames were performed using a Nikon D5300 digital SLR camera and a modified low-cost digital camera (Samsung Model NX3300), respectively. The three-dimensional UV and IR models were obtained using Agisoft PhotoScan^® software. The generated ultraviolet 3D model of the bust makes visible, in a single file, the fluorescence induced by UV radiation on the entire sculpture, highlighting surface abrasions, organic dyes, and ancient protective features. The infrared 3D model allowed for better definition of the details of the drawing used for eyes, nose and mouth definition. In conclusion, the ultraviolet fluorescence and IR 3D models of Saint Rodonio were particularly useful as documentation tools for the conservation status and for the painting construction, allowing us to perfectly map the original and restoration materials and to detect the drawing in single dynamic 3D files following a totally non-invasive, cost-effective, and rapid approach. Full article