EG GCH: EUROGRAPHICS Workshop on Graphics and Cultural Heritage

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Different Photogrammetric Approaches to 3D Survey of the Mausoleum of Romulus in Rome
(The Eurographics Association, 2014) Adami, Andrea; Cerato, Ivana; d'Annibale, Enzo; Demetrescu, Emanuel; Ferdani, Daniele; Reinhard Klein and Pedro Santos
In recent years, digital photogrammetry has enjoyed a renewed approval in the field of Cultural Heritage. This is due both to the relative cheapness of the instruments (a high resolution camera, possibly a reflex with good lenses) and to new algorithms and software that simplified the use, perhaps at the expense of the necessary knowledge of its principles. The 3D survey of the Mausoleum of Romulus, along the Via Appia Antica, within the European project 3DICONS, provided the opportunity to test different photogrammetric techniques, with the aim to verify the results and to evaluate the positive and negative aspects. In particular two different approaches have been applied: spherical photogrammetry and dense image matching. The first technique is based on traditional photogrammetric principles, applied on panoramic images instead of frame images. The second one, the most recent and very widespread, is inspired by traditional photogrammetry and computer vision. In order to have a significant and correct comparison, a topographic support has been realized for the Mausoleum, to have all surveyed data in a single local reference system. The comparison has been made by using, as a reference, the point cloud acquired by laser scanner. In this paper, after a description of the funeral monument and its complexity, the two techniques will be described in order to investigate pros and cons, their algorithm and application fields. The acquisition and processing stage will be described in order to give all the necessary elements for the final judgement. At the end of the restitution and modelling process, the comparison will take into account many parameters: the scheme of image acquisition, the time required (on-site and in laboratory), the hardware (for data acquisition and post-processing), the results that can be obtained (2d and 3D representations with texture) and the metric accuracy achieved. Finally there will be some hints about different applications of these methods as concerning above all the visualization of data. For example, the exploration of the Mausoleum can be done through the navigation of bubbles, obtained by spherical photogrammetry.
End-to-end Color 3D Reproduction of Cultural Heritage Artifacts: Roseninsel Replicas
(The Eurographics Association, 2019) Domajnko, Matevz; Tanksale, Tejas; Tausch, Reimar; Ritz, Martin; Knuth, Martin; Santos, Pedro; Fellner, Dieter W.; Rizvic, Selma and Rodriguez Echavarria, Karina
Planning exhibitions of cultural artifacts is always challenging. Artifacts can be very sensitive to the environment and therefore their display can be risky. One way to circumvent this is to build replicas of these artifacts. Here, 3D digitization and reproduction, either physical via 3D printing or virtual, using computer graphics, can be the method of choice. For this use case we present a workflow, from photogrammetric acquisition in challenging environments to representation of the acquired 3D models in different ways, such as online visualization and color 3D printed replicas. This work can also be seen as a first step towards establishing a workflow for full color end-to-end reproduction of artifacts. Our workflow was applied on cultural artifacts found around the ''Roseninsel'' (Rose Island), an island in Lake Starnberg (Bavaria), in collaboration with the Bavarian State Archaeological Collection in Munich. We demonstrate the results of the end-to-end reproduction workflow leading to virtual replicas (online 3D visualization, virtual and augmented reality) and physical replicas (3D printed objects). In addition, we discuss potential optimizations and briefly present an improved state-of-the-art 3D digitization system for fully autonomous acquisition of geometry and colors of cultural heritage objects.
Fully Automatic Mechanical Scan Range Extension and Signal to Noise Optimization of a Lens-Shifted Structured Light System
(The Eurographics Association, 2021) Kutlu, Hasan; Ritz, Martin; Santos, Pedro; Fellner, Dieter W.; Hulusic, Vedad and Chalmers, Alan
Digitization of cultural heritage is of growing importance, both for its preservation for coming generations in the face of looming dangers of natural decay or intentional destruction, and current generations, that increasingly have access to virtual cultural heritage for interactive exploring or scientific analysis. These goals can only be achieved by 3D replicas at reasonable quality and resolution, to come as close as possible to the original. This brings about several challenges to overcome. The challenge of digitizing huge numbers of artefacts is addressed by CultLab3D, the first fully automatic 3D digitization system. Another challenge is the size of objects, as each digitization system is designed for a certain optimum measurement range, leaving which results in loss of quality. Due to optical and mechanical constraints, most systems are not able to faithfully reconstruct objects under a certain size limit in their full geometric detail. Historic coins are one good example, where the deterioration of the surface structure in most cases has progressed to a degree that it not even is perceptible through the fingernail. This challenge is addressed by a modular extension of CultLab3D, the MesoScanner, which is a structured light system that breaks limits in depth resolution through a mechanical lens-shifting extension, allowing physically shifting of fringe patterns on top of the well-known multi-period phase shift method. This is where this work adds two major improvements: First, the signal to noise ratio and thus reconstruction quality has been improved significantly through several algorithmic processing steps. Second, the physical limitation of the measurement range was removed using a 2D actuator steering the object mount, thus allowing for a measurement range at theoretically arbitrary size. This opens up the fully automatic handling of two scenarios: Complete digitization of objects exceeding the measurement range, and unsupervised digitization of large collections of small objects in one run.
High Resolution 2D-/3D-Scanning and Deep Learning Segmentation for Digitization of Fragmented Wall Paintings
(The Eurographics Association, 2023) Kroeger, Ole; Krumpek, Oliver; Koch, Paul; Pape, Martin; Schneider, Jan; Krüger, Jörg; Bucciero, Alberto; Fanini, Bruno; Graf, Holger; Pescarin, Sofia; Rizvic, Selma
The preservation and study of mural wall paintings often involve the collection of numerous fragments with unknown context. In this paper the authors present a case study involving a Roman wall painting discovered in 2013 at the European Cultural Park Bliesbruck-Reinheim. The objective of this work was to develop a semi-automated assistance system for the digitization, visualization, and digital repositioning of the Roman wall painting fragments. Therefore an easy-to-use scanner system was developed, that captures high-resolution 2D images of the front and back surfaces of the fragments, along with a height map of the backside. The contributing partners also developed a control and operating software for the scanner, as well as an automated software platform for visualization and repositioning of the digital fragments. The contributions of this paper include the introduction of a ML-based algorithm for background subtraction and segmentation of the front surface of the fragments. The technical realisation for fast and accurate image acquisition of the fragments, including sensor registration and highresolution capture, has been worked out. The system calibration process, hardware setup and data correction techniques are described in detail. Additionally, the challenges of pixel-wise image segmentation for distinguishing between background, inner contour (wall painting), and outer contour (fragment surface without painting) are discussed. Our proposed approach overcomes the limitations of training ML algorithms on high-resolution images by employing patch-wise training and leveraging small features instead of large-scale features. The digitization and segmentation process demonstrated promising results in preserving and reconstructing the roman wall painting fragments. The findings of this study contribute to the field of cultural heritage preservation and provide valuable insights as the developed equipment and methods are highly transferable to future digitization projects.
An Investigation of Optimal Light Source Setups for Photometric Stereo Reconstruction of Historical Coins
(The Eurographics Association, 2018) Brenner, Simon; Zambanini, Sebastian; Sablatnig, Robert; Sablatnig, Robert and Wimmer, Michael
In this paper, we address the 3D reconstruction of historical coins by means of Photometric Stereo. We investigate the influence of the number and arrangement of lights to the reconstruction quality by comparing mean angular errors on 22 historical coin models. Our results demonstrate that 6 lights circularly placed at an optimal elevation angle do not show a significant loss of reconstruction quality compared to a full semispherical dome setup with 54 lights. This represents a considerable saving of acquisition time and system complexity when it comes to the mass digitization of historical coins.
Replicating perishable artefacts. A project for analysis and exhibition of Early Medieval objects from the Byzantine village at Scorpo (Supersano, Italy)
(The Eurographics Association, 2013) Bandiera, Adriana; Arthur, Paul; Imperiale, Marco Leo; Maffezzoli, Alfonso; Frigione, Mariaenrica; Montagna, Francesco; Signore, Grazia Maria; -
Artefacts found in an archaeological excavation are sometimes made of perishable or fragile material like wood, iron, or leather. These present obvious conservation problems. This is the case of various artefacts from the Byzantine village of Scorpo (Supersano, southern Italy) that has been the object of excavations by archaeologists from the University of Salento (Italy) since 1999. In 2007 a number of wooden objects were discovered in a well, while in 2012 a hoard of ferrous objects was found near a drystone wall that perhaps enclosed the settlement. Given the highly fragile and perishable nature of the objects, the questions arise as to how to study these artefacts, preserve them for the future and display them to the public. In this paper we will illustrate the methodology developed at the University of Salento to give an answer to all these questions and we will describe the entire process ranging from the discovery of the artefacts, to their 3D digital acquisition and modeling, the eventual digital restoration, the realization of one or more physical copies using a rapid prototyping apparatus (RP), to their display in a museum. Digital models of artefacts and ancient contexts are increasingly used in museums in order to improve communication, also for the disabled. Furthermore, the resin replica of an object, created from its digital 3D model, can also be useful for its preservation and fruition, especially if it is fragile or in poor condition.

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