GCH 2022 - Eurographics Workshop on Graphics and Cultural Heritage

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https://diglib.eg.org/handle/10.2312/2633215

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An Annotation Tool for Digital Restoration of Wall Paintings
(The Eurographics Association, 2022) Barreiro Díaz, Albert; Munoz-Pandiella, Imanol; Bosch, Carles; Andujar, Carlos; Ponchio, Federico; Pintus, Ruggero
Antique paintings are essential to study and understand our past. Paintings, and specifically mural paintings, are delicate artworks that are affected by multiple deterioration conditions. Weathering and human interventions cause different damage problems, and physical and chemical changes degrade their visual color appearance. As a consequence, art historians and archaeologists require a huge effort to attempt to rebuild their original appearance. The annotation of digital images of the paintings is a valuable tool in this process. In this paper we analyze major requirements from art historians concerning the annotation of painting regions from the point of view of digital restoration. We also describe a tool prototype (based on TagLab) intended to facilitate the annotation and segmentation of mural paintings. The tool assists art historians in formulating multiple hypotheses on the original appearance by supporting multiple annotation layers for degradation and color, providing both hand-drawn and semi-automatic segmentation, and offering web-based dissemination and sharing of the annotations through the W3C Web Annotation Data Model.
Audio Augmented Reality for Cultural Heritage Outdoors
(The Eurographics Association, 2022) Kritikos, Yannis; Giariskanis, Fotios; Protopapadaki, Eftychia; Papanastasiou, Anthi; Papadopoulou, Eleni; Mania, Katerina; Ponchio, Federico; Pintus, Ruggero
Audio Augmented Reality (AAR) is a novel area of AR representing the augmentation of reality with auditory input. The way auditory input is combined with 3D superimposed information in AAR is challenging, especially in noisy and busy environments outdoors. This paper presents a novel, work-in-progress, mobile AAR experience that is deployed in a city environment while walking past seven archaeological excavation sites in the city of Chania, Crete, Greece. The proposed AAR experience embeds 3D graphics and audio related to the cultural content while a visitor walks around the city, offering a non-linear narrative. Visual and audio digital elements are accurately geo-located while a personalized AAR SoundScape Generator boosts audience creativity. AAR design is optimized for outdoor use.
Automated Classification of Crests on Pottery Sherds Using Pattern Recognition on 2D Images
(The Eurographics Association, 2022) Ritz, Martin; Santos, Pedro; Fellner, Dieter W.; Ponchio, Federico; Pintus, Ruggero
Manual classification of artefacts is a labor intensive process. Based on 2D images and 3D scans of - for example - ceramic shards, we developed a pattern recognition algorithm which automatically extracts relief features for each newly recorded object and tries to automate the classification process. Based on characteristics found, previously unknown objects are automatically corelated to already classified objects of a collection exhibiting the greatest similarity. As a result, classes of artefacts form iteratively, which ultimately also corresponds to the overall goal which is the automated classification of entire collections. The greatest challenge in developing our software approach was the heterogeneity of reliefs, and in particular the fact that current machine learning approaches were out of question due to the very limited number of objects per class. This led to the implementation of an analytical approach that is capable of performing a classification based on very few artefacts.
A Concept for Reconstructing Stucco Statues from historic Sketches using synthetic Data only
(The Eurographics Association, 2022) Pöllabauer, Thomas; Kühn, Julius; Ponchio, Federico; Pintus, Ruggero
In medieval times, stuccoworkers used a red color, called sinopia, to first create a sketch of the to-be-made statue on the wall. Today, many of these statues are destroyed, but using the original drawings, deriving from the red color also called sinopia, we can reconstruct how the final statue might have looked. We propose a fully-automated approach to reconstruct a point cloud and show preliminary results by generating a color-image, a depth-map, as well as surface normals requiring only a single sketch, and without requiring a collection of other, similar samples. Our proposed solution allows real-time reconstruction on-site, for instance, within an exhibition, or to generate a useful starting point for an expert, trying to manually reconstruct the statue, all while using only synthetic data for training.
Context-based Surface Pattern Completion of Ancient Pottery
(The Eurographics Association, 2022) Lengauer, Stefan; Preiner, Reinhold; Sipiran, Ivan; Karl, Stephan; Trinkl, Elisabeth; Bustos, Benjamin; Schreck, Tobias; Ponchio, Federico; Pintus, Ruggero
Among various ancient cultures it was common practice to adorn pottery artifacts with lavish surface decoration. While the applied painting styles, color schemes and displayed mythological content may vary greatly, the presence of simple patterns which appear in a repetitive manner can be observed across civilizations and periods. Such pattern sequences generally are arranged in a structured manner in ornament bands or columns that extend over the entire surface of the object. Due to the poor conservation state of many cultural heritage objects, parts of the surface are oftentimes badly damaged or missing altogether. Yet, if the majority of a pattern sequence is preserved, this information can be leveraged to approximate its missing parts. We present an approach that allows the fully automatic determination of the generation rule inherent to a repetitive surface pattern. Based on this generation rule and the preserved patterns from the same pattern class we propose a workflow for reconstruct missing or damaged parts of the surface painting. We evaluate our approach by applying it to a selection of pottery from ancient Peruvian and Greek cultures, showing that our automatic approach is able to handle a variety of problem cases.
A Course on the Digital Humanities for the Premodern World
(The Eurographics Association, 2022) Rushmeier, Holly; Chen, Anne; Ponchio, Federico; Pintus, Ruggero
With the roots of digital humanities in text-centric disciplines, coursework has traditionally focused on instruction in skills of relevance for text-based resources, while digital methods for non-textual sources have remained in the minority. We describe a digital humanities course targeted at undergraduate computer science majors and graduate students in cultural heritage adjacent fields. The course foregrounds a specific blend of text-based and visual methods of relevance to practitioners in cultural heritage fields. Acknowledging that digital projects in the humanities are more often than not cross-disciplinary and collaborative, the course is designed to emphasize visual computing techniques while helping students develop experience in cross-disciplinary communication. The requirements for the two groups are different to ensure that all students are challenged. The course includes a substantial group project. Each group is composed of both humanities and computer science students and the project goal is defined by the humanities students. The purpose of the project is both to apply methods learned in the course and to learn collaboration in a team with individuals with different levels and types of expertise.
Digital 3D Documentation Curation Platform for Cultural Heritage Sites
(The Eurographics Association, 2022) Ferraz, António; Nóbrega, Rui; Correia, Nuno; Ponchio, Federico; Pintus, Ruggero
Using an abandoned stronghold under renovation as a cultural heritage use case, this paper focuses on methods for the creation of a digital documentation platform that aims at the preservation of both the physical site, through the recreation of a 3D environment, and the intangible historical and sociocultural elements through an interactive game like experience. The result is a solution that allows the user to explore a 3D environment while observing the recreated structures of the stronghold based on 3D models, and the development of interactive methods to promote the visualization of historical content placed in such environment. The solution also allows the evolution of the system, making it possible to rearrange and curate the environment into different setups. The system went through an evaluation process where users tested the diverse features and the results express a positive response from the users towards the usability of the platform, as well as a positive opinion on the virtualization of the historical site and the interactive methods for content visualization.
Digital Reintegration of Distributed Mural Paintings at Different Architectural Phases: the Case of St. Quirze de Pedret
(The Eurographics Association, 2022) Munoz-Pandiella, Imanol; Argudo, Oscar; Otzet, Immaculada Lorés; Comas, Joan Font; Casademont, Genís Àvila; Pueyo, Xavier; Andujar, Carlos; Ponchio, Federico; Pintus, Ruggero
Sant Quirze de Pedret is a Romanesque church located in Cercs (Catalonia, Spain) at the foothills of the Pyrenees. Its walls harbored one of the most important examples of mural paintings in Catalan Romanesque Art. However, in two different campaigns (in 1921 and 1937) the paintings were removed using the strappo technique and transferred to museums for safekeeping. This detachment protected the paintings from being sold in the art market, but at the price of breaking the integrity of the monument. Nowadays, the paintings are exhibited in the Museu Nacional d'Art de Catalunya - MNAC (Barcelona, Catalonia) and the Museu DiocesÃ i Comarcal de Solsona - MDCS (Solsona, Catalonia). Some fragments of the paintings are still on the walls of the church. In this work, we present the methodology to digitally reconstruct the church building at its different phases and group the dispersed paintings in a single virtual church, commissioned by the MDCS. We have combined 3D reconstruction (LIDAR and photogrammetric using portable artificial illumination) and modeling techniques (including texture transfer between different shapes) to recover the integrity of the monument in a single 3D virtual model. Furthermore, we have reconstructed the church building at different significant historical moments and placed actual paintings on its virtual walls, based on archaeological knowledge. This set of 3D models allows experts and visitors to better understand the monument as a whole, the relations between the different paintings, and its evolution over time.
Ebb & Flow: Uncovering Costantino Nivola's Olivetti Sandcast through 3D Fabrication and Virtual Exploration
(The Eurographics Association, 2022) Ahsan, Moonisa; Altea, Giuliana; Bettio, Fabio; Callieri, Marco; Camarda, Antonella; Cignoni, Paolo; Gobbetti, Enrico; Ledda, Paolo; Lutzu, Alessandro; Marton, Fabio; Mignemi, Giuseppe; Ponchio, Federico; Ponchio, Federico; Pintus, Ruggero
We report on the outcomes of a large multi-disciplinary project targeting the physical reproduction and virtual documentation and exploration of the Olivetti sandcast, a monumental (over 100m2) semi-abstract frieze by the Italian sculptor Costantino Nivola. After summarizing the goal and motivation of the project, we provide details on the acquisition and processing steps that led to the creation of a 3D digital model. We then discuss the technical details and the challenges that we have faced for the physical fabrication process of a massive physical replica, which was the centerpiece of a recent exhibition. We finally discuss the design and application of an interactive web-based tool for the exploration of an annotated virtual replica. The main components of the tool will be released as open source.
Lithic Feature Identification in 3D based on Discrete Morse Theory
(The Eurographics Association, 2022) Bullenkamp, Jan Philipp; Linsel, Florian; Mara, Hubert; Ponchio, Federico; Pintus, Ruggero
Neanderthals and our human ancestors have coexisted for a large period of time sharing many things in common including the production of tools, which are among the few remaining artefacts providing a possible insight into the different paths of evolvement and extinction. These earliest tools were made of stone using different strategies to reduce a rather round stone to a sharp tool for slicing, scraping, piercing or chopping. The type of strategy is assumed to be correlated either with our ancestors or the Neanderthals. Recent research uses computational methods to analyse shapes of lithic artefacts using Geometric MorphoMetrics (GMM) as known in anthropology. As the main criteria for determining a production strategy are morphologic measures like shape, size, roughness of convex ridges and concave scars, we propose a new method based on discrete Morse theory for surface segmentation to enable GMM analysis in future work. We show the theoretical concepts for the proposed segmentation, which have been applied to a dataset being available via Open Access. For validation we have created a statistically significant subset of segmented simple and complex lithic tools, which have been manually segmented by an expert as ground truth. We finally show results of our experiments on this real dataset.
Multispectral Imaging for Historical Artifacts: A Case Study Using an 8th-Century Biblical Scroll
(The Eurographics Association, 2022) Arnold, Etta; Moyer, Izzy; Bourgeois, Alana; Mei, Parker; Decker, Juilee; Easton Jr., Roger; Messinger, David; Ponchio, Federico; Pintus, Ruggero
Many objects of interest in cultural heritage, such as manuscripts, scrolls, and books are faded, damaged, or otherwise unreadable so that useful studies of them are difficult. Fortunately, modern imaging tools, including sensors, lenses, and illumination sources have leveraged multispectral imaging as an accessible method for cultural heritage imaging which has, in turn, increased the demand for its use. To address this, the Rochester Institute of Technology received a grant from the National Endowment for the Humanities (PR-268783-20) to develop a low-cost, portable imaging system with processing software that could be utilized by scholars accessing collections in library, archive, and museum settings, as well as staff working within these institutions. This article gives an overview of this system and uses an 8th-century Hebrew manuscript as a case study to demonstrate the impact of such a low-cost, low barrier-to-entry system on cultural heritage research, preservation, and dissemination.
A New Baseline for Feature Description on Multimodal Imaging of Paintings
(The Eurographics Association, 2022) Toorn, Jules van der; Wiersma, Ruben; Vandivere, Abbie; Marroquim, Ricardo; Eisemann, Elmar; Ponchio, Federico; Pintus, Ruggero
Multimodal imaging is used by conservators and scientists to study the composition of paintings. To aid the combined analysis of these digitisations, such images must first be aligned. Rather than proposing a new domain-specific descriptor, we explore and evaluate how existing feature descriptors from related fields can improve the performance of feature-based painting digitisation registration. We benchmark these descriptors on pixel-precise, manually aligned digitisations of ''Girl with a Pearl Earring'' by Johannes Vermeer (c. 1665, Mauritshuis) and of ''18th-Century Portrait of a Woman''. As a baseline we compare against the well-established classical SIFT descriptor. We consider two recent descriptors: the handcrafted multimodal MFD descriptor, and the learned unimodal SuperPoint descriptor. Experiments show that SuperPoint starkly increases description matching accuracy by 40% for modalities with little modality-specific artefacts. Further, performing craquelure segmentation and using the MFD descriptor results in significant description matching accuracy improvements for modalities with many modalityspecific artefacts.
Scan2FEM: From Point Clouds to Structured 3D Models Suitable for Simulation
(The Eurographics Association, 2022) Selman, Zain; Musto, Juan; Kobbelt, Leif; Ponchio, Federico; Pintus, Ruggero
Preservation of cultural heritage is important to prevent singular objects or sites of cultural importance to decay. One aspect of preservation is the creation of a digital twin. In case of a catastrophic event, this twin can be used to support repairs or reconstruction, in order to stay faithful to the original object or site. Certain activities in prolongation of such an objects lifetime may involve adding or replacing structural support elements to prevent a collapse. We propose an automatic method that is capable of transforming a point cloud into a geometric representation that is suitable for structural analysis. We robustly find cuboids and their connections in a point cloud to approximate the wooden beam structure contained inside. We export the necessary information to perform structural analysis, on the example of the timber attic of the UNESCO World Heritage Aachen Cathedral. We provide evaluation of the resulting cuboids' quality and show how a user can interactively refine the cuboids in order to improve the approximated model, and consequently the simulation results.
Semi-Automatic Perspective Lines from Paintings
(The Eurographics Association, 2022) Coudert-Osmont, Yoann; Eisemann, Elmar; Marroquim, Ricardo; Ponchio, Federico; Pintus, Ruggero
Perspective cues play an important role in painting analysis as it may unveil important characteristics about the painter's techniques and creation process. Nevertheless, extracting perspective lines and their corresponding vanishing points is usually a laborious manual task. Moreover, small variations in the lines may lead to large variations in the vanishing points. In this work, we propose a semi-automatic method to extract perspective lines from paintings in order to mitigate the human variability factor and reduce the workload.
Tactile prints in colour: Studying the Visual Appearance of 2.5D Prints for Heritage Recreations
(The Eurographics Association, 2022) Trujillo-Vazquez, Abigail; Rodriguez Echavarria, Karina; Weyrich, Tim; Ponchio, Federico; Pintus, Ruggero
Printing applications for heritage recreation are a means to allow audiences to appreciate details and engage with cultural materials through closer interaction. A 2.5D print is a media suitable to incorporate visual and tactile qualities such as colour, low relief, textures and roughness. Designing a colour-accurate tactile print requires, nevertheless, anticipating how specific shapes and meso-geometries will affect the reflective properties of the surface, thus changing its appearance. Hence, this paper contributes to improve the understanding of the interaction between geometry and colour when deploying 2.5D prints so that tactile portable replicas can be easily produced. For this, we have produced a series of 2.5D printed patches with varying meso-textures, based on procedural noise functions, and measured their colour coordinates and glossiness. We aim to find a correlation between colour shift (expressed as lightness, chroma and ?E) and the scale and distribution of surface details.
Visual Analysis of RIS Data for Endmember Selection
(The Eurographics Association, 2022) Popa, Andra; Gabrieli, Francesca; Kroes, Thomas; Krekeler, Anna; Alfeld, Matthias; Lelieveldt, Boudewijn; Eisemann, Elmar; Höllt, Thomas; Ponchio, Federico; Pintus, Ruggero
Reflectance Imaging Spectroscopy (RIS) is a hyperspectral imaging technique used for investigating the molecular composition of materials. It can help identify pigments used in a painting, which are relevant information for art conservation and history. For every scanned pixel, a reflectance spectrum is obtained and domain experts look for pure representative spectra, called endmembers, which could indicate the presence of particular pigments. However, the identification of endmembers can be a lengthy process, which requires domain experts to manually select pixels and visually inspect multiple spectra in order to find accurate endmembers that belong to the historical context of an investigated painting. We propose an integrated interactive visual-analysis workflow, that combines dimensionality reduction and linked visualizations to identify and inspect endmembers. Here, we present initial results, obtained in collaboration with domain experts.

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