GCH 2018 - Eurographics Workshop on Graphics and Cultural Heritage

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https://diglib.eg.org/handle/10.2312/2632673

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New Haven Building Archive: A Database for the Collection, Study, and Communication of Local Built Heritage
(The Eurographics Association, 2018) Rubin, Elihu; Akhtar, Saima; Brown, Benedict; Rushmeier, Holly; Sablatnig, Robert and Wimmer, Michael
The New Haven Building Archive (NHBA) is a digital, mobile, and interactive field guide to New Haven, Connecticut's built heritage. As an interactive digital guide and database for local buildings, the NHBA harnesses digital mapping technologies, place-based storytelling and community-based research. Ultimately, the development of the NHBA will aid in the co-production of knowledge about the city by students, academic researchers and local citizens in a way that will facilitate conversations about the historical patterns and future development of New Haven while suggesting a model for engaged teaching and research for urban studies more broadly.
Deep Mapping Tarn Hows: Automated Generation of 3D Historic Landscapes
(The Eurographics Association, 2018) Reinhold, Alexander; Gregory, Ian; Rayson, Paul; Sablatnig, Robert and Wimmer, Michael
Changing landscape presents a problem for both conservation and education at heritage sites. We consider the site of Tarn Hows in the English Lake District National Park, a site which has had significant landscape change over the past 200 years, from developing tree coverage, to the merging of three lakes into one. We created an automated process that combines an elevation map and a vegetation map to build a 3D representation of the landscape. We used this tool to create a 3D Deep Map of Tarn Hows, representing the site's landscape at multiple periods over time, allowing them to be viewed side by side and explored in an interactive environment. This 3D Deep Map provides an exploratory resource for site authorities to educate the public about the historic environment, with embedded multimedia in the application to provide additional information to users that might be disruptive or impractical to display on site. The 3D Deep Map also provides a tool for conservators to plan site maintenance to best maintain the integrity of the historic landscape without negatively impacting visitors' experience of the iconic site.
Elastic Flattening of Painted Pottery Surfaces
(The Eurographics Association, 2018) Preiner, Reinhold; Karl, Stephan; Bayer, Paul; Schreck, Tobias; Sablatnig, Robert and Wimmer, Michael
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 pottery.
Multiple Material Layer Visualization for Cultural Heritage Artifacts
(The Eurographics Association, 2018) Moutafidou, Anastasia; Adamopoulos, Georgios; Drosou, Anastasios; Tzovaras, Dimitrios; Fudos, Ioannis; Sablatnig, Robert and Wimmer, Michael
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 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 work.
Integrated Volume Visualisation of Archaeological Ground Penetrating Radar Data
(The Eurographics Association, 2018) Bornik, Alexander; Wallner, Mario; Hinterleitner, Alois; Verhoeven, Geert; Neubauer, Wolfgang; Sablatnig, Robert and Wimmer, Michael
The non-invasive prospection of our archaeological heritage is one of the main tasks of modern archaeology and often provides the necessary bases for further activities, such as special protection or intensified research. Geophysical prospections using ground-penetrating radar (GPR) are an invaluable tool for the non-destructive exploration of archaeological monuments still buried in the ground. However, the analysis and interpretation of the data sets generated in this way is a time-consuming and complex process and requires not only three-dimensional imagination but also a broad understanding of the archaeological remains. Therefore, understandable 3D visualisations are in great demand. This paper presents a novel integrated visualisation approach, which supports conjoint visualisation of scenes composed of heterogeneous data including GPR volumes and 3D models of interpretations and reconstructions. Visual depiction of relevant dataset areas and archaeological structures is facilitated based on flexible and localised visualisation techniques. Furthermore, the rendering system supports the computation of dynamic label layouts for scenes annotations.
Visualising Dudsbury Hillfort: Using Immersive Virtual Reality to Engage the Public with Cultural Heritage
(The Eurographics Association, 2018) John, David; Hurst, David; Cheetham, Paul; Manley, Harry; Sablatnig, Robert and Wimmer, Michael
Whilst computer visualisation is an established method of presenting cultural heritage, the use of game engines to provide a full immersive virtual reality experience is less well developed. This research documents the development of a visualisation of an Iron Age hillfort using Unreal Engine together with LiDAR terrain data to create a fully immersive experience for the virtual visitor. The visualisation was evaluated by 36 members of the public. The results show a high degree of satisfaction with the visualisation and agreement with the results of other studies demonstrating significant differences between those new to and those familiar with virtual reality applications. The conclusion is that in combination, game engines and LiDAR are effective tools for creating engaging virtual heritage visualisations.
Earthquake Simulation for Ancient Building Destruction
(The Eurographics Association, 2018) Fita, Josep Lluis; Besuievsky, Gonzalo; Patow, Gustavo; Sablatnig, Robert and Wimmer, Michael
Research on seismic simulations has been focused mainly on methodologies specially tailored for civil engineering. On the other hand, we have detected a certain lack of this kind of tools for interactive cultural heritage applications, where speed and plausibility are the main requirements to satisfy. We have designed a tool that allows to parameterize and recreate real earthquakes in an accurate, but simple way. Furthermore, we have focused our efforts on those users without much technical experience in geology or seismic simulation, such as historians, art historians, museum curators and other similar stakeholders. We have performed a series of tests over a set of ancient masonry buildings such as walls with their respective battlements, houses and a Romanesque church with structural simulation enabled, thus, allowing the coupling between the earthquake being simulated and the objects of interest. We show the feasibility of including earthquake simulations and structural stability into historical studies for helping the professionals to understand better those events of the past where an earthquake took place.
Gloss Calibration and Gloss Gamut Mapping for Material Appearance Reproduction of Paintings
(The Eurographics Association, 2018) Elkhuizen, Willemijn S.; Essers, Tessa T. W.; Song, Yu; Pont, Sylvia C.; Geraedts, Jo M. P.; Dik, Joris; Sablatnig, Robert and Wimmer, Michael
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 Cornelis 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 values.
Data Visualization of Decoration Occurrence and Distribution. A Comparative Study of Late Egyptian Funerary Decoration in Thebes
(The Eurographics Association, 2018) Wutte, Anja; Sablatnig, Robert and Wimmer, Michael
Decoration in Ancient Egyptian funerary monuments represents an important part of the monuments layout. Beside scenes displaying the owner, scenes of daily life, fabrication, offerings and hieroglyphic texts are found. Not only topics of self-presentation but also decoration for the translation to the afterlife were predominant. Therefore, this paper suggests approaches to analyze distribution and occurrence of decorations of several ancient monuments of the same style, with data visualization and quantitative methods. As a case study ancient Egyptian funerary monuments of High Officials from the Late Period, twenty-fifth to twenty-sixth dynasty, were studied. The decorative scenes were categorized and tagged in terms of their content. The positions in the monument were highlighted and included in abstracted 3-dimensional models. This computational implementation offers users to search for decoration categories, highlight, locate and finally compare the position of a scene between the monuments. The visualized data include the position and orientation of a categorized scene in the monument, their occurrence and distribution among the analyzed monuments. In a further step the analysis data was studied statistically in order to be able to query detailed results of the prevalence, distribution and preservation of decorations and specific scenes. Both introduced solutions provide a user friendly information interface to visualize, compare and request quantitative data.
Development of a High Resolution Topography and Color Scanner to Capture Crack Patterns of Paintings
(The Eurographics Association, 2018) Hengstum, Mathijs J. W. van; Essers, Tessa T. W.; Elkhuizen, Willemijn S.; Dodou, Dimitra; Song, Yu; Geraedts, Jo M. P.; Dik, Joris; Sablatnig, Robert and Wimmer, Michael
The aging of paintings is inevitable and over the years degradation occurs due to exposure to a variety of environmental influences. One of these degradations is craquelure, fracture patterns in the paint. 3D imaging techniques offer opportunities to capture the surface of a painting and these patterns at high resolution. In this paper we present a 3D scanner that is able to capture surface topography and color of oil paintings at high resolution utilizing fringe-encoded stereo imaging scanning system. The scanner is capable of automated capture of an area of 1x1m2, capturing a painting at a spatial resolution of 7 micron and a depth accuracy of 34 microns. Scanning at this resolution creates potential research opportunities for documentation and monitoring oil paintings under its environmental influences. A scan was made of 'Girl with a Pearl Earring' (c.1665), painted by Johannes Vermeer, which exhibits fine craquelure patterns. The scanner is able to capture the painting of 39x44.5 cm within 2 hours with a tile overlap of 25%. The results showed that the craquelure has more often a ridge-shaped profile instead of the expected inward valleys. The documentation of these variations in crack profiles create interesting paths for future research.
On Combining Epigraphy, TLS, Photogrammetry, and Interactive Media for Heritage Documentation: The Case Study of Djehutihotep's Tomb in Dayr al-Barsha
(The Eurographics Association, 2018) Lima, Roberto de; Sykora, Toon; Meyer, Marleen De; Willems, Harco; Vergauwen, Maarten; Sablatnig, Robert and Wimmer, Michael
The governors' tombs located at Dayr al-Barsha are considered among the most important monuments of the Egyptian Middle Kingdom. Unfortunately, due to quarrying activities, looting, and natural catastrophes, the archaeological remains are now in a dilapidated state. Their documentation therefore becomes a necessary task towards the preservation and research of this provincial elite cemetery. Traditional geomatics-based heritage recording methods and sensors are, however, not sufficient to yield a full and comprehensive documentation. Inspired by emergent technologies, this paper proposes a symbiosis of digital epigraphy, Terrestrial Laser Scanning (TLS), image-based digitalization techniques, and 3D visualization platforms, to provide experts with a digital tool able to yield high-level information in terms of accurate digital drawings of decorated sections and dense 3D mesh models. Results show that the proposed approach provides a reliable alternative to answer research questions, especially in the context of ancient Egyptian heritage, as the level of detail captured enables the academic community to further explore decoration techniques, damage recognition, and digital reconstruction.
Virtual Restoration of Wooden Artifacts by Non-Rigid 3D Shape Assembly: A Case of the First Solar Boat of King Khufu
(The Eurographics Association, 2018) Nemoto, Takashi; Kobayashi, Tetsuya; Oishi, Takeshi; Kagesawa, Masataka; Kurokochi, Hiromasa; Yoshimura, Sakuji; Ziddan, Eissa; Taha, Mamdouh; Sablatnig, Robert and Wimmer, Michael
In this paper, we present a method to digitally reassemble an object to its original form given the 3D data of its component which are assumed to be non-rigidly deformed. Targeting wooden artifacts, we developed an algorithm to deform the components parametrically, and constraints based on the physical properties of wood are imposed on the deformation. We apply our method to a deformed cultural asset, specifically the first solar boat of King Khufu which is made of wood.
Aging Prediction of Cultural Heritage Samples Based on Surface Microgeometry
(The Eurographics Association, 2018) Ciortan, Irina Mihaela; Marchioro, Giacomo; Daffara, Claudia; Pintus, Ruggero; Gobbetti, Enrico; Giachetti, Andrea; Sablatnig, Robert and Wimmer, Michael
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 time.
Objective and Subjective Evaluation of Virtual Relighting from Reflectance Transformation Imaging Data
(The Eurographics Association, 2018) Pintus, Ruggero; Dulecha, Tinsae; Jaspe, Alberto; Giachetti, Andrea; Ciortan, Irina; Gobbetti, Enrico; Sablatnig, Robert and Wimmer, Michael
Reflectance Transformation Imaging (RTI) is widely used to produce relightable models from multi-light image collections. These models are used for a variety of tasks in the Cultural Heritage field. In this work, we carry out an objective and subjective evaluation of RTI data visualization. We start from the acquisition of a series of objects with different geometry and appearance characteristics using a common dome-based configuration. We then transform the acquired data into relightable representations using different approaches: PTM, HSH, and RBF. We then perform an objective error estimation by comparing ground truth images with relighted ones in a leave-one-out framework using PSNR and SSIM error metrics. Moreover, we carry out a subjective investigation through perceptual experiments involving end users with a variety of backgrounds. Objective and subjective tests are shown to behave consistently, and significant differences are found between the various methods. While the proposed analysis has been performed on three common and state-of-the-art RTI visualization methods, our approach is general enough to be extended and applied in the future to new developed multi-light processing pipelines and rendering solutions, to assess their numerical precision and accuracy, and their perceptual visual quality.
Towards an Automatic 3D Patterns Classification: the GRAVITATE Use Case
(The Eurographics Association, 2018) Thompson, Elia Moscoso; Biasotti, Silvia; Sorrentino, Giusi; Polig, Martina; Hermon, Sorin; Sablatnig, Robert and Wimmer, Michael
When cataloging archaeological fragments, decorative patterns are an indicator of the stylistic canon an object belongs to. In this paper we address a quantitative classification of the decorative pattern elements that characterize the models in the GRAVITATE use case, discussing the performance of a recent algorithm for pattern recognition over triangle meshes.
Multi-Light Energy Map
(The Eurographics Association, 2018) Lardeux, Florian; Marchand, Sylvain; Gomez-Krämer, Petra; Sablatnig, Robert and Wimmer, Michael
We propose a model to represent quasi-flat objects, such as coins or amphora stamps. These objects are flat surfaces, meaning their length and their width largely exceed their height, and feature a distinctive relief. This relief characterizes the object and its perception is directly influenced by the position of the object, the light direction and the viewer's direction. Our model is a single image representation containing the underlying structural variations of the object. This model, that we call 'Multi-Light Energy Map', is constructed out of several classic images taken with several illumination directions without computing the object's surface normals. We found a way to extract useful information out of this sequence of images and compile it into our map. We eventually explain how we can use this model in the case of image registration of ancient coins.
Towards the Reconstruction of Wide Historical Sites: A Local Graph-based Representation to Resample Gigantic Acquisitions
(The Eurographics Association, 2018) Bletterer, Arnaud; Payan, Frédéric; Antonini, Marc; Meftah, Anis; Sablatnig, Robert and Wimmer, Michael
Nowadays, LiDAR scanners are able to digitize very wide historical sites, leading to point clouds composed of billions of points. These point clouds are able to describe very small objects or elements disseminated in these sites, but also exhibit numerous defects in terms of sampling quality. Moreover, they sometimes contain too many samples to be processed as they are. In this paper, we propose a local graph-based structure to deal with the set of LiDAR acquisitions of a digitization campaign. Each acquisition is considered as a graph representing the local behavior of the captured surface. Those local graphs are then connected together to obtain a single and global representation of the original scene. This structure is particularly suitable for resampling gigantic points clouds. We show how we can reduce the number of points drastically while preserving the visual quality of large and complex sites, whatever the number of acquisitions.
Proxy Painting
(The Eurographics Association, 2018) Lange, Vanessa; Kurth, Philipp; Keinert, Benjamin; Boss, Martin; Stamminger, Marc; Bauer, Frank; Sablatnig, Robert and Wimmer, Michael
For archaeologists it is often desireable to present statues in their original coloration. With projection mapping real-world surfaces are augmented by digital content to create compelling alterations of the scene's visual appearance without actually altering or even damaging the object. While there are frequent advances in projection quality, content creation is still a chal- lenging and often unintuitive task, especially for non-experts. In our presented system we combine the advantages of digital content creation such as rapid prototyping with the convenience of an analog workflow. Users paint on smaller versions of the projection mapping target, employing real-world brushes and pencils, while the results are presented live on its large counter- part. We further demonstrate the integration of our system into a state-of-art game engine. By leveraging a powerful rendering and material workflow we make creating compelling materials and lighting situations an intuitive experience.
Shape Analysis Techniques for the Ayia Irini Case Study
(The Eurographics Association, 2018) Scalas, Andreas; Vassallo, Valentina; Mortara, Michela; Spagnuolo, Michela; Hermon, Sorin; Sablatnig, Robert and Wimmer, Michael
The typical approach for archaeological analysis is mainly qualitative and, as such, subjective. Even when some measures are reported in the documentation of artefacts, they are often approximate or ambiguous. Conversely, the quantitative approach is based on objective metrics to produce replicable results and, coupled with digital tools, can assist the qualitative analysis in archaological research with no risk of damage. In this paper, we present a geometric-quantitative approach for the analysis of archaeological finds and the preliminary results of an ongoing joint research project of two doctoral students within the frame of the EU GRAVITATE project.
An Image-based Approach for Detecting Faces Carved in Heritage Monuments
(The Eurographics Association, 2018) Lai, Yu-Kun; Echavarria, Karina Rodriguez; Song, Ran; Rosin, Paul L.; Sablatnig, Robert and Wimmer, Michael
Heritage monuments such as columns, memorials and buildings are typically carved with a variety of visual features, including figural content, illustrating scenes from battles or historical narratives. Understanding such visual features is of interest to heritage professionals as it can facilitate the study of such monuments and their conservation. However, this visual analysis can be challenging due to the large-scale size, the amount of carvings and difficulty of access to monuments across the world. This paper makes a contribution towards this goal by presenting work-in-progress for developing image-based approaches for detecting visual features in 3D models, in particular of human faces. The motivation for focusing on faces is the prominence of human figures throughout monuments in the world. The methods are tested on a 3D model of a section of the Trajan Column cast at the Victoria and Albert (V&A) Museum in London, UK. The initial results suggest that methods based on machine learning can provide useful tools for heritage professionals to deal with the large-scale challenges presented by such large monuments.

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