Abstract: Conventionally, visitors of exhibitions cannot directly interact with artworks but remain mainly passive. This work presents a new way to discover paintings through an extended reality application with the aim of enhancing visitors’ engagement. The workflow consists of digitally recreating a painting. All its constitutive elements are contoured and then removed by the artwork. These elements will be unveiled by the visitors with gesture interaction. The discovery of each element is followed by additional information on the subject. The application also proposes an alternative experience where the user paints the components of the artwork with gestures. The hands’ position was tracked by the Leap Motion Controller, an optical sensor by Ultraleap. The process has been applied to one of the Tintoretto’s pieces of art: “L’Annunciazione del Doge Grimani”. The extended reality application has been experienced by over twenty thousand visitors at the dedicated exhibition. Numerous positive comments received from both visitors and guides are encouraging.

Keywords: Cultural heritage | Exhibition | Extended reality | User interaction

Abstract: This paper presents a Generative Design Method (GDM) for highly customised Cultural Heritage applications concerning the exhibition and conservation of pottery. As a fundamental requirement, archaeological finds must be preserved in their structural integrity. Additionally, when present, the exposition supports must be aesthetically pleasant meaning that they must be non-invasive in the field of view of the observer. Furthermore, each artefact presents a unique geometry, hence its supporting structure must be designed accordingly. The proposed GDM considers these requirements, adopting a synergy of CAD, CAE, and optimisation tools. It is developed through two phases. The first phase, P1, concerns with the structural integrity of the fragment. In this phase, a Parametric Modelling approach is chosen for its ease of use both in the Finite Element Analysis evaluations of artefacts and in the design and optimisations of feasible supporting structures. The output of the phase P1 is the optimised configuration of the functional elements of the support ('Ci ') which are the interface region between the support itself and the fragment of pottery. They represent the input of the second phase, P2, that aims to generate lightweight concepts for the complete supporting structure considering the optimal 'Ci ' configuration. During this phase, an aesthetics criterion (related to the minimisation of the support's visibility) is also considered to achieve non-invasive supporting structures. Doing so, the GDM provides informed decisions in the early stages of the design activities with a simulation driven approach oriented to manufacturing. In this way, users are able to focus on design requirements since the concept's variants are generated by means of an optimised configuration of standardised components ('Ci') and obstacle geometries.

Keywords: Cultural Heritage | Generative Design | Parametric Modelling | Parametric Optimisation

Abstract: The study of potteries is still today almost entirely performed manually by archaeologists. The primary limits of the traditional approach are lack of repeatability in the results, the time required for the analysis and difficulty in exchanging information between researchers. Taking advantage of the previous research results obtained by the Authors in this field, a fully automated procedure for the analysis and cataloguing of potteries is presented in this paper. The procedure allows performing the geometric and semantic analysis of sherds, starting from their 3D scanned model. The method can also determine a set of meaningful measurements of the analyzed sherds and classify them according to the analysis results. Finally, the results are collected into a public and web-based application, which can be interacted with by interested people.

Keywords: 3D database | Computer-aided procedure | Pottery analysis | Semantic segmentation

Abstract: Ceramics analysis, classification, and reconstruction are essential to know an archaeological site's history, economy, and art. Traditional methods used by the archaeologists for their investigation are time-consuming and are neither reproducible nor repeatable. The results depend on the operator's subjectivity, specialization, personal skills, and professional experience. Consequently, only a few indicative samples with characteristic components are studied with wide uncertainties. Several automatic methods for analysing sherds have been published in the last years to overcome these limitations. To help all the involved researchers, this paper aims to provide a complete and critical analysis of the state-of-the-art until the end of 2021 of the most important published methods on pottery analysis, classification, and reconstruction from a 3D discrete manifold model. To this end, papers in English indexed by the Scopus database are selected by using the following keywords: “computer methods in archaeology”, “3D archaeology”, “3D reconstruction”, “3D puzzling”, “automatic feature recognition and reconstruction”. Additional references complete the list found through the reading of selected papers. The 125 selected papers, referring to only archaeological potteries, are divided into six groups: 3D digitalization, virtual prototyping, Fragment features processing, geometric model processing of whole-shape pottery, 3D Vessel reconstruction from its fragments, classification, and 3D information systems for archaeological pottery visualization and documentation. In the present review, the techniques considered for these issues are critically analysed to highlight their pros and cons and provide recommendations for future research.

Keywords: Automatic features recognition | Computer methods in archaeology | Computer-based methods for sherds classification and reconstruction | Mesh segmentation | Pottery profile detection | Pottery profile dimensions

Abstract: The dimensional characterization of archaeological fragment is a very complex operation and could prove to be useful for identifying the presence of standard attributes in the ceramics found from a specific archaeological site, or for making comparisons and analysis of similarities or for studying ancient technologies used for manufacture of objects. The dimensional analysis of the fragments is now carried out manually with traditional measuring devices. Typically, the results obtained are inaccurate and non-repeatable measurements. This paper focuses on the dimensional characterization of a specific geometric class of features: the constant radius swept features (called here CRS features). Several archaeological features, such as rims, bases, decorative motifs, processing marks and grooves are referable from a geometric point of view to the class of CRS features. These are detail features, which may be very interesting for the investigation of some aspects related to the historical-archaeological classification of the find. CRS features are often found on worn, damaged (e.g. chipped) or fragmented objects; they are frequently characterized, from a geometric point of view, by free form surfaces and by a limited cross sectional extension. In some cases, CRS features can be of axially symmetrical geometry: this occurs quite frequently in the case of archaeological pottery. For all these reasons, it is often difficult to apply traditional manual methods for the quantitative dimensional characterization of CRS features. This paper describes an original methodology for the measurement of CRS features acquired by scanning technologies. The algorithmic implementation of this methodology, consisting of a suitable processing of the feature nodes, allows to carry out automatically the dimensional characterization of the feature.

Abstract: The traditional manual method of analysis of ceramic finds involves expert operators in long and routine activities whose results depend on their subjectivity, specialization, and professional experience. This implies that the analysis of sherds is carried out using few data affected by high uncertainty. These limitations are even more clear with fragments with small axially symmetric portions whose elements of the investigation are not axially symmetric, such as handles, spouts, decorations. In this way both the axis of symmetry of the original object and the reference planes and/or axes of the characteristic dimensions of the elements are identified with such approximations as to compromise subsequent analyses and comparisons. To overcome these limitations, in this paper a new computer-based procedure is proposed. As a case study, the analysis fragments of jugs/bowls with trilobed spouts found in the site of Amiternum, coming from 12th-13th century contexts are considered; their analysis is fundamental to analyze the site where they were found since there is no archival documentation about their use.

Abstract: The sweep features of constant radius are particularly significant for the purposes of the historical-archaeological investigation and classification of ancient artifacts. The paper focuses on the automatic recognition of this specific class of features from triangulated 3D models experimentally acquired from cultural heritage objects. This is not a trivial problem. The ancient artifacts, although repeatable, are unique handmade pieces with a geometry commonly characterized by complex and non-analytical shapes. Their surfaces are also usually damaged and worn, so that the related geometric properties are altered or lost. The methodology proposed here is inspired by the one previously developed by the authors for the automatic segmentation of fillets, rounds and grooves from high-density triangulated models of mechanical components. The paper, in particular, focuses on the aspects of this methodology that must be tuned to allow the recognition of the sweep features of constant radius from archaeological finds. The methodology has been implemented and finally applied to an archaeological find acquired by a laser scanner.

Keywords: 3D archaeology | 3D digital models | Computer methods in archaeology | Feature recognition | Laser scanning

Abstract: The knowledge of the history, economy, and art of an archeological site is based on information that can be taken from ceramics analysis, classification, and reconstruction. The traditional methods used by the archeologists for their investigation are time-consuming, not reproducible, and repeatable, and the results depend on the subjectivity, specialization, personal skills, and professional experience of the operator. An as consequence, only a few indicative samples that have characteristic components are analyzed with wide uncertainties. In order to overcome these limitations, in the last years, some automatic methods for studying archeological pottery’s findings are proposed in the literature. To help all the researchers involved in this field, this paper aims to provide a complete and critical analysis of the state-of-the-art until the end of 2020 of the published methods on pottery classification and reconstruction from a 3D discrete manifold model. For this purpose, papers in English by the Scopus database are collected by using the following keywords: “computer methods in archaeology”, “3D archaeology”, “3D reconstruction”, “automatic feature recognition and reconstruction”, “3D puzzling”. The list is completed by additional references found through the reading of selected papers. The 35 selected papers are divided into three groups: Geometric model fragment processing, 3D information systems for archaeological pottery visualization and documentation, 3D puzzling of archaeological fragments. The results of the present review are focused on the presentation of the pros and cons of the techniques used on these different issues.

Keywords: 3D archaeology | Automatic feature recognition | Computer methods in archaeology | Computer-based methods for sherd classification and reconstruction | Surface segmentation

Abstract: UAV Photogrammetry is a quite widely use technology for 3D reconstruction of territory, thanks to its satisfying results in many fields of applications and its low cost. Most of researches that addressed this topic use Ground Control Points (GCPs) for scaling and georeferencing the acquired point-cloud. In this paper, due to the particular morphology of the surveyed territory that makes very difficult to define GCPs in the region of interest, an innovative technique based on geometrical features was used for orienting, scaling and georeferencing the 3D point-cloud. The case is the ancient Roman outlet of the Fucino emissary, sited in a very steep and not accessible area, near Capistrello (AQ) city, Italy. The obtained results show that the proposed methodology, although less accurate than standard one using GCPs, provides quite good results, so that it can be used where the use of GCPs is difficult or impossible.

Keywords: Archaeology | Feature-based alignment | UAV photogrammetry

Abstract: In the Cultural Heritage field, the choice of materials and exhibit structures is essential to properly house and support artifacts without causing damage or deterioration. This problem is even more evident in the case of finds made of stone for which, due to their weight, a proper selection and dimensioning of the relative supports is required. In fact, without adequate support, this can result in stress concentrations that could compromise the artifact's state of conservation. As a consequence, more often such exhibition supports are customized items, that are designed and manufactured to meet specific functional and artistic setup needs. In this context, the paper presents a design approach that combines topology optimization and additive manufacturing techniques to develop customized support structures which undertake the twofold purpose of preserving the artifact and making it available for the exhibition in the museum. The proposed approach has been assessed through the case study of a sandstone Ionic capital hosted in the Brettii & Enotri Museum in Cosenza (Italy). The proposed approach is therefore meant as a guideline for the design of customized exhibit supports especially in the case of sandstone artifacts with a complex shape or a conservation condition that requires specific attention.

Keywords: Additive manufacturing | Cultural heritage | Design methods | Exhibit supports | Photogrammetry | Topology optimization

Abstract: Mechanical design and engineering can support projects with high-added value in the Cultural Heritage field, such as restoration of artefacts like statues and architectonical decorations. Many examples have been carried out, along the recent past, in the field of ancient bronze restorations (as for Marco Aurelio, Satiro Danzante di Mazara del Vallo and Principe Ellenistico). Engineering design techniques help the assessment of structural problems through physical measurements and FEA simulations; the digital acquisition of surfaces represents a fundamental base for CAD modelling, and the inner frame design helps for guaranteeing stability and manoeuvrability requirements for transport and exhibition. Workflow peculiarities and requirements to accomplish the restorers’ activities and investigations may highlight best practices and rules. The design of the new inner frame of the Vittoria Alata of Brescia, an ancient roman bronze statue, represents a recent example of this kind. Its design workflow was provided in the loop of the restoration program, and it was assessed considering structural integrity, surfaces protection, inner inaccessibility, and dimensions. The solutions adopted are the result of a collaborative process with restorers to evaluate each proposed concept, in compliance with the studies and the constraints highlighted during the investigations. CAD-CAE tools applied starting from the 3D acquisition, helped the development and its verification, reducing the efforts during the manufacturing phase and final set-up. This paper aims to discuss the obtained result demonstrating how structural analysis and mechanical design anchored to 3D acquisitions may help restoration of bronze statues.

Keywords: CAD-CAE | Cultural heritage | Design for restoration | Structural analysis | Vittoria Alata

Abstract: Nowadays, restoration is a multidisciplinary work that gathers knowledge and skills from different areas (technical, artistic, historical, architectural, …). In the field of ancient bronze statues, technical knowledge may also concern with materials behaviour and its preservation, surface quality, non-destructive diagnostics for integrity, a better understanding of the manufacturing technology, and of details, sometimes hidden, in not directly accessible sections of the artefact. This knowledge, got from different domains, can support restorers in their decision-making process. In many cases, they summarise it on pictorial views of the artefacts, or on images derived from the 3D model that is experimentally acquired through reverse engineering, to reference information on the interested areas. The aim of this paper is to explore the advantages related to a CAD-based framework able to gather the technical domains involved in the restoration of historical artifacts. Doing so, CAD functionalities and related benefits may be extended to cultural heritage applications as tools oriented for restoration, according to a life cycle perspective of the restorer’s activities and the artefact preservation and fruition. The proposed CAD-based framework has been implemented to manage the investigation for restoration and conservation of bronze statues. The approach has been applied to the Principe Ellenistico, part of the collection of Palazzo Massimo, one of the sites of Museo Nazionale Romano (in Rome). The obtained results show that the CAD-based framework may speed-up the investigation processes without losing accuracy and restorers’ good practices.

Keywords: CAD-CAE | Cultural heritage | Design for restoration | Principe Ellenistico | Virtual prototyping

Abstract: In the last years, interactive exhibitions based on digital technologies have become widely common, thanks to their flexibility and effectiveness in engaging visitors and creating memorable experiences. One of the topics in which digital technologies can be particularly effective is the communication of abstract concepts that are difficult for the human mind to imagine. An emblematic example is the astronomy discipline, which requires us to imagine and understand phenomena far away from our everyday life. In this paper, the authors present a research project, MARSS, in which digital technologies are used effectively to enhance the Users’ Experience of the Museo Astronomico di Brera located in Milan. Specifically, the MARSS project aims at designing and developing a new digital journey inside the museum to allow different categories of visitors to enjoy the exhibition in an engaging and interactive way. The paper presents the design and development phases of the experience and its evaluation with users. The results of the evaluation indicate that the digital interactive experience is appreciated by users and is successful in translating the content of high scientific value into more engaging and easily understandable elements.

Keywords: augmented reality | cultural heritage | extended reality | interactive exhibitions | science museums | user experience

Abstract: The field of simplification of geometric surfaces still lacks a formal and universally recognized definition of the error, which should involve both the approximation of the shape and the conservation of the other attributes of the mesh (starting from the colour). In order to solve this problem, we propose a hypothesis of methodological comparison that allow the evaluation of differences between two homologous surfaces, quantified employing the Hausdorff distance. The main advantage of this method is the independence from sampling techniques used to produce the mesh, without losing its characteristics of objectivity and generality. The Hausdorff distance geometrically represents the distance between two sets A and B in a suitable metric space, and it is defined as the maximum between the excess of A over B and the excess of B over A. This value is then compared with the average length of the diagonals of the “bounding boxes” of the homologous models, i.e. the parallelepipeds corresponding to the minimum volume that completely envelops each set; this results in an effective representation of error in relative terms.

Keywords: Accuracy assessment | Cultural Heritage | Hausdorff distance | Mesh

Abstract: From archaeological excavations, huge quantities of material are recovered, usually in the form of fragments. Their correct interpretation and classification are laborious and time-consuming and requires measurement, analysis and comparison of several items. Basing these activities on quantitative methods that process 3D digital data from experimental measurements allows optimizing the entire restoration process, making it faster, more accurate and cheaper. The 3D point clouds, captured by the scanning process, are raw data that must be properly processed to be used in automatic systems for the analysis of archeological finds. This paper focuses on the integration of a shape feature recognizer, able to support the semantic decomposition of the ancient artifact into archaeological features, with a structured database, able to query the large amount of information extracted. Through the automatic measurement of the dimensional attributes of the various features, it is possible to facilitate the comparative analyses between archaeological artifacts and the inferences of the archaeologist and to reduce the routine work. Here, a dedicated database has been proposed, able to store the information extracted from huge quantities of archaeological material using a specific shape feature recognizer. This information is useful for making comparisons but also to improve the archaeological knowledge. The database has been implemented and used for the identification of pottery fragments and the reconstruction of archaeological vessels. Reconstruction, in particular, often requires the solution of complex problems, especially when it involves types of potsherds that cannot be treated with traditional methods.

Keywords: 3D archaeology | Computer methods in archaeology | Information search and retrieval | Measurement precision in archaeol-ogy | Similarity metric

Abstract: The problem of matching fragments of three-dimensional (3D) objects has gained increasing attention, and several approaches have been developed to solve this problem. To date, however, to the best knowledge of the authors, there is no computer-based method supporting archaeologists in this activity. For this purpose, in this paper, a semi-automatic approach is proposed for the reconstruction of archaeological pottery fragments based on two-dimensional (2D) images. Firstly, the method, considering the curves as features, involves the extraction of edge curves by applying the Canny filter algorithm to the fragments’ image. Next, the wavelet transformation method is used to fit the edge curves and obtain the approximation coefficients. Then, the correlation coefficients between fragments are computed and the matching of fragments is done by comparing their values. The proposed approach is tested on some real cases. The results of the experimentation show, if compared with the state-of-the-art, that the method seems to be efficient and accurate in the reconstruction of pottery from 2D images of their fragments.

Keywords: Edge detection | Pottery fragment | Reconstruction | Wavelet transformation

Abstract: The protection of artistic and cultural heritage is a major challenge due to its peculiarities and its exposure to significant natural hazards. Several methodologies exist to assess the condition of artistic heritage and to protect it from exceptional actions. Moreover, novel digital technologies offer many solutions able to deliver a digital replica of artifacts of interest, so that a reduction in the uncertainties in the analysis models can be achieved. A rational approach to the preservation and protection of artistic heritage is based on traditional approaches supported and integrated by novel technologies, so that qualitative and quantitative indicators of the current condition of artistic heritage can be defined and validated in an interdisciplinary framework. The present paper reports the results of an approach to the maintenance and preservation of art objects housed in a museum complex based on a comprehensive digital path towards a Historical Digital Twin (HDT). A workflow aimed at estimating the stress regime and the dynamic properties of two sculptures, based on the detailed three-dimensional model resulting from a laser scanner survey, is illustrated and dis-cussed. The results highlight the great advantages resulting from the integration of traditional and novel procedures in the field of conservation of artistic assets.

Keywords: 3D simulation | Conservation | Cultural heritage | Digital twin | Laser scanning | Maintenance

Abstract: In the last decades, the popularity of video games has been increasing thanks to their unique ability to engage their audience and create empathy. Among them, serious games have additional purposes besides entertainment, such as learning and behaviour change. Serious games, in fact, have been successfully applied to different fields, including education, health, tourism, and cultural heritage. In this context, the paper describes a novel serious game developed for increasing awareness and promoting the Underwater Cultural Heritage (UCH). In particular, the paper focuses on the Dive in the Past Serious Game which allows users to simulate a virtual dive into the Mediterranean Sea to explore accurate and life-sized 3D reconstructions of underwater archaeological sites. The purpose of the game is twofold: to engage diver and non-diver tourists into a virtual interactive exploration of underwater sites through digital storytelling and challenges; to increase awareness and knowledge on Mediterranean UCH. This work has been carried out in the context of the MeDryDive project, an EU co-funded under the COSME Programme, which aims to create personalized dry dive experiences for the promotion of Mediterranean UCH sites as distinctive tourism destinations.

Keywords: 3D reconstruction | Mediterranean Sea | Serious game | Underwater archaeology | Underwater Cultural Heritage

Abstract: In situ protection and conservation of the Underwater Cultural Heritage are now considered a primary choice by the scientific community to be preferred, when possible, over the practice of recovery. The conservation of the artefacts within their environmental context is essential in fact for a correct interpretation of archaeological presences and to preserve their true value intact for future generations. However, this is not an easy task because modern technological equipment is necessary to make the work carried out by underwater restorers and archaeologists faster and more efficient. To this end, the paper presents three innovative underwater power tools for the cleaning, conservation, and consolidation activities to be performed in submerged archaeological sites. The first one is an underwater cleaning brush tool for a soft cleaning of the underwater archaeological structures and artefacts; the second one is a multifunctional underwater hammer drill suitable to be used as a corer sampler, chisel, or drill; the last one is an injection tool specifically designed to dispense mortar underwater for consolidation techniques of submerged structures.

Keywords: In situ preservation | Product design | Underwater archeology | Underwater cultural heritage | Underwater power tools

Abstract: Underwater cultural heritage sites represent an attractive and exciting experience for diving tourists, even if often it is complicated for them to understand the significance and value of the remains that are usually strongly damaged and covered by the marine organisms. Thanks to the recent advancements in technologies that overcome these problems, augmented reality is nowadays possible even in such harsh conditions, opening new possibilities for enhancing the diver's experience. However, no user study has formally evaluated the usefulness and usability of augmented reality in open sea underwater environments. This paper presents two novel solutions for underwater augmented reality: a compact marker-based system for small areas, and a complex acoustic system for large areas. Both of them were deployed at an underwater cultural heritage site and evaluated by ten divers in experiments analyzing their perception and remembrance, interests, and user experience. For comparison, the same study was also performed with non-divers assessing the marker-based system on land. Results show that both systems allow divers to encounter new and exciting moments and provide valuable insights for underwater augmented reality applications.

Keywords: Augmented reality | cultural heritage | sensor fusion | underwater | user experience | user testing

Abstract: The paper addresses an image processing problem in the field of fine arts. In particular, a deep learning-based technique to classify geometric forms of artworks, such as paintings and mosaics, is presented. We proposed and tested a convolutional neural network (CNN)-based framework that autonomously quantifies the feature map and classifies it. Convolution, pooling and dense layers are three distinct categories of levels that generate attributes from the dataset images by introducing certain specified filters. As a case study, a Roman mosaic is considered, which is digitally reconstructed by close-range photogrammetry based on standard photos. During the digital transformation from a 2D perspective view of the mosaic into an orthophoto, each photo is rectified (i.e., it is an orthogonal projection of the real photo on the plane of the mosaic). Image samples of the geometric forms, e.g., triangles, squares, circles, octagons and leaves, even if they are partially deformed, were extracted from both the original and the rectified photos and originated the dataset for testing the CNN-based approach. The proposed method has proved to be robust enough to analyze the mosaic geometric forms, with an accuracy higher than 97%. Furthermore, the performance of the proposed method was compared with standard deep learning frameworks. Due to the promising results, this method can be applied to many other pattern identification problems related to artworks.

Keywords: Convolutional neural networks | Cultural heritage | Deep learning algorithm | Image-based reconstruction | Pattern classification

Abstract: In the last years, museums have begun to apply new technological solutions to manage their exhibits in a more open, inclusive, and creative way, to improve the visitors' experience to respond to the need to expand the audience. The main goal is to face the increasing competition in an economy referred to as the “Experience Economy”. To this end, Augmented Reality technology seems to represent a good solution for museum guide systems, to improve visitors' learning and enjoyment. In this context, the present paper proposes a museum guide system based on Spatial Augmented Reality powered by dynamic projection. The paper describes the overall HW and SW system architecture and reports in detail the developed process adopted to design and implement a museum guide and entertainment application, in the context of the “Studiolo of Federico da Montefeltro” in the Ducal Palace of Urbino. A preliminary survey has been carried out, which involved a total of 79 subjects, aimed at investigating the quality of visitor's experience, aroused by the proposed application, in terms of the “Four Experience Realms” defined by Pine & Gilmore (1998). Results suggest that the proposed application can be used to stage experiences that satisfy the visitors and may help to enable museums into the Experience Economy.

Keywords: Cultural heritage | Dynamic projection | Experience economy | Museum guide | Spatial augmented reality

Abstract: This paper introduces a new recommendation system for museums able to profile the visitors and propose them the most suitable exhibition path accordingly, to improve visitors’ satisfaction. It consists of an interactive touch screen totem, which implements a USB camera and exploits Convolutional Neural Network to perform facial coding to measure visitors’ emotions and estimate their age and gender. Based on the detected level of emotional valence, the system associates visitors with a profile and suggests them to visit a selection of five works of art, following a specific itinerary. An extensive experimentation lasting 2 months has been carried out at the Modern Art Museum “Palazzo Buonaccorsi” of Macerata. Results evidence that the proposed system can create an interactive and emotional link with the visitors, influencing their mood in the Pre-Experience phase and in the subsequent Post-Experience phase. In particular, they highlight that the proposed system, which aims at acting as emotional leverage, has been able to improve the positiveness of the emotions experienced by the visitors.

Keywords: Affective computing | Cultural heritage | Emotion recognition | Facial expression recognition

Abstract: Current conservation approaches are shifting toward small, tailored, and less invasive interventions. Therefore the problems and best practices for conservators are becoming increasingly mobile. The future of art preservation heating systems will be with “intelligent” devices that are portable, flexible, reliable, and cost-effective. In this scenario, flexible heaters are becoming the preferred device for the application of heat in restoration since they can be shaped in different geometries and sizes, are easy to be transported and can be applied in the most versatile way with other treatment devices. Moreover, such devices can be applied also for in situ treatments, for instance, in emergency interventions. The development of these flexible devices comes from the past and, therefore, has a long history. To provide the reader with a comprehensive description of most innovative heating devices for art conservation, this chapter provides a brief history on how such devices evolved from the beginning to now, with the final aim of understanding the technological challenges and issues that allowed to continuously improve traditional heat tables and wound wire-based blankets toward the creation of innovative carbon nanotubes (CNTs)-based devices. After an historical investigation of heating devices, mostly based on heat tables, the chapter focuses on current technologies where nanomaterials are increasingly being used to boost the heating performance in several fields of application. Finally this work describes the main outcomes of a recent European Project, which applied CNTs-based coating on flexible substrates to create the first prototypes of intelligent mobile heaters to be adopted extensively by conservators. A number of applications of this new kind of device are eventually proposed and discussed.

Keywords: Carbon nanotubes | Coatings | Cultural heritage | Heating mat

Abstract: Potteries are the most numerous finds found in archaeological excavations; they are often used to get information about the history, economy, and art of a site. Archaeologists rarely find complete vases but, generally, damaged and in fragments, often mixed with other pottery groups. By using the traditional manual method, the analysis and reconstruction of sherds are performed by a skilled operator. Reviewed papers provided evidence that the traditional method is not reproducible, not repeatable, time-consuming and its results have great uncertainties. To overcome the aforementioned limits, in the last years, researchers have made efforts to develop computer-based methods for archaeological ceramic sherds analysis, aimed at their reconstruction. To contribute to this field of study, in this paper, a comprehensive analysis of the most important available publications until the end of 2019 is presented. This study, focused on pottery fragments only, is performed by collecting papers in English by the Scopus database using the following keywords: "computer methods in archaeology", "3D archaeology", "3D reconstruction", "automatic feature recognition and reconstruction", "restoration of pottery shape relics". The list is completed by additional references found through the reading of selected papers. The 53 selected papers are divided into three periods of time. According to a detailed review of the performed studies, the key elements of each analyzed method are listed based on data acquisition tools, features extracted, classification processes, and matching techniques. Finally, to overcome the actual gaps some recommendations for future researches are proposed.

Keywords: 3D archaeology | 3D reconstruction | Automatic feature recognition and reconstruction | Computer methods in archaeology | Restoration of pottery shape relics

Abstract: The registration permits to positioning in a single reference system point clouds acquired from different points of view. Since this is typically obtained with an iterative numerical method, it represents an important source of error in the entire reverse engineering process. As all iterative methods, such errors depend on the choice of the initial solution; therefore, this process requires an expert user who, by using dedicated software, choices the sequence of clouds to be registered, imposes for each pairwise the first attempt registration, launches the iterative method, and verifies the final result. With the aim to minimize the error and the user's interaction, some devices are proposed in the market (turntable or the anthropomorphic arm, etc.). The above-mentioned hardware and software tools cannot be used in the cultural heritage applications involving large and detailed objects. In this paper, an automatic alignment method of point clouds is proposed. The method uses as inputs the constant radius features, which are frequently detectable on cultural heritage objects. The automatic alignment of the point clouds is based on the recognition, the segmentation, and the registration of the sweep lines identifiable from these features.

Abstract: This paper presents a combined subjective and objective evaluation of an application mixing interactive virtual reality (VR) experience with 360◦ storytelling. The hypothesis that the modern immersive archaeological VR application presenting cultural heritage from a submerged site would sustain high levels of presence, immersion, and general engagement was leveraged in the investigation of the user experience with both the subjective (questionnaires) and the objective (neurophysiological recording of the brain signals using electroencephalography (EEG)) evaluation methods. Participants rated the VR experience positively in the questionnaire scales for presence, immersion, and subjective judgement. High positive rating concerned also the psychological states linked to the experience (engagement, emotions, and the state of flow), and the experience was mostly free from difficulties linked to the accustomization to the VR technology (technology adoption to the head-mounted display and controllers, VR sickness). EEG results are in line with past studies examining brain responses to virtual experiences, while new results in the beta band suggest that EEG is a viable tool for future studies of presence and immersion in VR.

Keywords: 360-video storytelling | Cultural heritage | EEG | Immersion | Presence | Virtual reality

Abstract: Kandinsky-Experience Book is a multisensory Augmented Reality experience that involves sight, hearing and smell senses and aims at improving the users’ engagement in the Kandinsky’s artworks. Specifically, the aim of the application is to augment the experience of the user creating a journey throughout Kandinsky's work by using an AR application for smartphones integrated with audio and olfactory stimuli, in order to allow him/her to be more immersed in the piece of art. The research project has been inspired by the synesthetic approach of the abstract painter to the theory and the perception of art in his books. Starting from the artist’s considerations about the relationship between different sensorial stimuli in works of art, we decided to amplify some of his theories suggesting a connection between the main pictorial elements and some corresponding olfactory stimuli, grounding our hypotheses on the content of papers concerning the crossmodal synesthetic correspondences between olfactory stimuli and other sensorial modalities. Thanks to the simultaneous presentation of the specifically developed AR contents and the olfactory stimuli, the users’ feelings and emotions during the experience are amplified as a result of the sensory integration. Moreover, by using AR technology and olfactory devices to stimulate visual and olfactory perceptual channels we aimed at increasing the generation of longer-lasting memories in the users' mind.

Keywords: Augmented Reality | Cultural Heritage | Multisensory Perception | User Experience

Abstract: In recent years, the development in digital technologies such as Augmented Reality (AR) and Virtual Reality (VR) has evolved rapidly. These technologies are currently in the process of creating driving change in the Cultural and Creative Industries (CCIs), representing innovative means to share information, facilitating access and increasing the value and public awareness on Cultural and Natural Heritage. This is particularly relevant for underwater environments, where the most interesting cultural and naturalistic sites are accessible only to scuba divers, or not accessible at all, due to depth and/or environmental constraints. In addition, in underwater sites, guided diving tours are carried out by professionals that usually describe the area to be visited during the predive briefings; such step is needed due to the impossibility of underwater verbal communication without dedicated equipment, a practice very rarely adopted for recreational diving. So, these difficulties make it almost impossible to replicate under the sea, the guided tour approach that is usually offered in on‐land museums. Considering such limitations, several technological applications are emerging to increase the accessibility underwater and enrich users’ experience both for divers and nondivers. This work aims to identify the potential of underwater sites (either cultural or natural) to support the development of sustainable tourism (economic, environmental, cultural and social) in the Mediterranean. Moreover, it focuses on supplying local/regional authorities and stakeholders with a multidisciplinary plan for managing Underwater Museums and Knowledge Centres, by promoting innovation in the diving industry and improving users’/tourists’ experience through value‐added services and cutting‐edge technologies.

Keywords: Diving tourism | Sustainable tourism | Underwater cultural heritage | Virtual diving

Abstract: Ceramic sherds are the most common finds in archaeology. They are complex to analyze and onerous to process. A large number of indistinct sherds coming from excavations must be preliminarily grouped in some categories. This clusterization helps the next phase, in which archaeologists classify the ceramics. Due to the difficulty of these preliminary, repetitive, and routine phases, a great deal of archaeological material remains unstudied in museum repositories or archaeological sites. An effective method to automate these routine phases is presented in this article. The proposed method performs a shape feature segmentation of the sherds, which is fundamental to undertake any further analysis, such as potsherds classification, reconstruction, or cataloging. A set of specific shape features, useful to understand the find properties, is defined and methods for recognizing them are proposed. The method's performance is tested in the analysis of some real, critical cases.

Keywords: 3D archaeology | Automatic feature recognition | computer methods in archaeology | surface segmentation

Abstract: In the region of the cultural patrimony, operators use high-resolution orthophotos of paintings for the restoration, monitoring and electronic recording and exhibition purposes. Unfortunately, artworks that are to be restored and/or shown in digital museums are painted on canvas that are far from perfectly planar. Professional documents surrounding an artwork to be preserved in digital collections or museums can therefore be enhanced with information relating to the paintings' 3D structure. This paper proposes both the design of a portable low-cost device that enables the acquisition of 3D geometry of painting and the procedure for triangulation of 3D data. This process uses a set of fiducial markers to set and continuously control the mutual orientation of the laser source and the camera and works accordingly to the principle of laser-camera triangulation.

Keywords: 3D Laser Scanner | Cultural Heritage | Marker Detection | Pose Estimation | Reverse Engineering

Abstract: In the field of cultural heritage, operators make use of high resolution orthophotos of paintings both for purposes related to restoration and monitoring of art pieces and for realizing online documentations and exhibitions. Unfortunately, artworks to be restored and/or presented in digital museums are painted on canvas which are far to be perfectly planar. Therefore, technical documentation accompanying an artwork to be stored in digital archives or museums can be enriched by information related to the 3D shape of the canvas. In this paper, both the design of a portable low-cost device that allows the acquisition of the 3D geometry of the painting and a procedure to triangulate 3D data are proposed. Such a procedure, working using the principle of laser-camera triangulation, is based on the use of a set of fiducial markers to set and continuously control the reciprocal orientation of the laser source and of the camera.

Keywords: 3D laser scanner | Cultural heritage | Marker detection | Pose estimation | Reverse engineering

Abstract: The construction of the artificial emissary of Fucino Lake is one of the most ambitious engineering buildings of antiquity. It was the longest tunnel ever made until the 19th century and, due to the depth of the adduction inlet, it required a monumental and complex incile, which, for functionality, cannot be compared to other ancient emissaries. The Roman emissary and its "incile" (Latin name of the inlet structure) were almost completely destroyed in the 19th century, when Fucino Lake was finally dried. Today, only few auxiliary structures such as wells, tunnels, and winzes remain of this ancient work. As evidence of the ancient incile remains a description made by those who also destroyed it and some drawings made by travelers who, on various occasions, visited the site. This paper presents a virtual reconstruction of the Roman incile, obtained both through the philological study of the known documentation, interpreting iconographic sources that represent the last evidence of this structure, and through the survey on the territory. The main purpose is to understand its technical functionalities, the original structures, and its evolution during the time, taking into account the evolution of the Fucino Lake water levels, technological issues, and finally o_ering its visual reconstruction.

Keywords: 3D virtual reconstruction This research received no external funding | Archaeology | Monumental heritage | Remote sensing

Abstract: The classification of ceramic archaeological fragments is based on shape, dimensions, decorations, technological elements, color and material. Nowadays, all of these features are still recognized and analyzed by a skilled operator. It follows that the resulting characterization of shape and sizes of archaeological fragments is poorly reproducible and repeatable. With a view to overcome these limitations, a computer-based methodology, able to extract automatically several quantitative information from high-density discrete geometric models acquired by the laser scanning of archaeological fragments, was proposed. In this paper, the set of quantitative information obtainable is furtherly broadened, by including the segmentation of some types of morphological features, the identification of the fragment shape type, the evaluation of the longitudinal profile and the estimation of a larger set of dimensional features. Finally, a new 3D information framework is proposed to store the large variety of quantitative information extracted.

Abstract: This paper gives a contribution to the automatic recognition of significant features of ancient ceramics, useful for the historical and/or archeological investigation. These very common type geometric features are obtained by a sweeping action that leaves negative or positive traces, characterized by a cross section with one or more constant radii. The paper proposes a novel methodology that, analyzing the principal curvatures at the points of high-density geometric models of ceramic vessels, acquired by laser scanning, identifies the nodes potentially attributable to these features of constant radius. The recognition process is not trivial since it is affected by uncertainties. To overcome the limits of a recognition based on crisp sets, the recognition rule, proposed for the feature segmentation, is implemented by a fuzzy approach. The method has been tested in the identification of embossed decorations in an ancient olla and it proves to be promising for further applications on other types of geometric features of constant radius.

Abstract: The study of the immense patrimony of ceramic finds is still performed by the traditional manual archaeological approach. So that, the information of the shape and dimensions of the sherds have high uncertainties, are expensive and time consuming to be obtained. With the aim to overcome these limitations, for several years our research group has directed efforts to the development of an automatic computer-based method for the morphological and dimensional characterization of axially-symmetric shards. In this paper, the salient points of this method are reported, as well as the management system of all gathered information. The 3D information system is designed for its future use for pottery classification and reconstruction of ancient ceramics.

Abstract: The Lake Fucino's emissary represents one of the most important hydraulic construction realized in antiquity. Unfortunately, little remains of the original structure of the Roman emissary, obliterated by the Torlonia building and the definitive drying of the lake. This article presents its virtual reconstruction, in order to understand survey and technological issues met by Romans and to visually offer reconstruction theories, interpreting a partially lost evidence of the Roman technology. The engineering resource becomes the means for a deeper comprehension of archaeological questions, combining the tools of engineering and archeology.

Abstract: The Mediterranean Sea has a vast maritime heritage which exploitation is made difficult because of the many limitations imposed by the submerged environment. Archaeological diving tours, in fact, suffer from the impossibility to provide underwater an exhaustive explanation of the submerged remains. Furthermore, low visibility conditions, due to water turbidity and biological colonization, sometimes make very confusing for tourists to find their way around in the underwater archaeological site. To this end, the paper investigates the feasibility and potentials of the underwater Augmented Reality (UWAR) technologies developed in the iMARECulture project for improving the experience of the divers that visit the Underwater Archaeological Park of Baiae (Naples). In particular, the paper presents two UWAR technologies that adopt hybrid tracking techniques to perform an augmented visualization of the actual conditions and of a hypothetical 3D reconstruction of the archaeological remains as appeared in the past. The first one integrates a marker-based tracking with inertial sensors, while the second one adopts a markerless approach that integrates acoustic localization and visual-inertial odometry. The experimentations show that the proposed UWAR technologies could contribute to have a better comprehension of the underwater site and its archaeological remains.

Keywords: Markerless and marker-based tracking | Underwater acoustic localization | Underwater augmented reality | Underwater cultural heritage

Abstract: The paper presents the digital technologies developed in the VISAS project and their application to the underwater archaeological site of Cala Minnola (Levanzo Island, Italy)that preserves the remains of a Roman ship. Following the basic principles defined by UNESCO for the protection of the Underwater Cultural Heritage the VISAS project has led to the development of innovative digital technologies for a more engaging and educational exploitation of the submerged archaeological sites. In particular, the paper describes a virtual diving system that allows users to perform, outside of the submerged environment, a virtual exploration of the Cala Minnola shipwreck site. Moreover, an augmented diving system provides, through an underwater tablet, a geolocalized multimedia guide for the divers that visit the underwater archaeological site. Both digital technologies allow users to perform an entertaining and interdisciplinary learning experience by receiving archaeological, historical, and biological information of the specific submerged site.

Keywords: Underwater 3D reconstruction | Underwater archaeology | Underwater Cultural Heritage | Virtual exploitation | Virtual reality

Abstract: 3D models of submerged structures and underwater archaeological finds are widely used in various and different applications, such as monitoring, analysis, dissemination, and inspection. Underwater environments are characterised by poor visibility conditions and the presence of marine flora and fauna. Consequently, the adoption of passive optical techniques for the 3D reconstruction of underwater scenarios is a highly challenging task. This article presents a performance analysis conducted on a multi-view technique that is commonly used in air in order to highlight its limits in the underwater environment and then provide guidelines for the accurate modelling of a submerged site in poor visibility conditions. A performance analysis has been performed by comparing different image enhancement algorithms, and the results have been adopted to reconstruct an area of 40 m2 at a depth of about 5 m at the underwater archaeological site of Baiae (Italy).

Keywords: 3D reconstruction | Image enhancement | Underwater Cultural Heritage | Underwater imaging

Abstract: Interventions of ancient bronze statues restoration may last long periods, involving several activities from material and structural analysis to set-up of museum exhibitions, passing through reconstruction of fragments. In this paper, we describe procedures and methods used for evaluation of the current posture of “Principe Ellenistico”. In fact, the statue seems to present some inaccuracies, in the fragments assembly, made during the last restoration activity (one of this effect is clearly observed in the spear inclination). The final aims are: (1) evaluation of differences among the postures before and after the last restoration; (2) recognition of the original fragments embedded in a previous restoration; and (3) the study of a possible better positioning of them. Methods applied are related to feature recognition on acquired point clouds, image analysis through control points and algorithms to find centerline of the elements that could need to be repositioned. In the final part, a concept design for a new inner-support is presented, giving the possibility to avoid assembly inaccuracies. Future developments are presented as the prospect of additive manufacturing the support, firstly with a FDM prototype and then through SLM or similar technologies.

Keywords: 3D-reconstruction | Bronze statue restoration | Cultural heritage | Feature recognition | Virtual prototyping

Abstract: Augmented reality can be deployed in various application domains, such as enhancing human vision, manufacturing, medicine, military, entertainment, and archeology. One of the least explored areas is the underwater environment. The main benefit of augmented reality in these environments is that it can help divers navigate to points of interest or present interesting information about archaeological and touristic sites (e.g., ruins of buildings, shipwrecks). However, the harsh sea environment affects computer vision algorithms and complicates the detection of objects, which is essential for augmented reality. This paper presents a new algorithm for the detection of fiducial markers that is tailored to underwater environments. It also proposes a method that generates synthetic images with such markers in these environments. This new detector is compared with existing solutions using synthetic images and images taken in the real world, showing that it performs better than other detectors: it finds more markers than faster algorithms and runs faster than robust algorithms that detect the same amount of markers.

Keywords: Augmented reality | Cultural heritage | Generating synthetic images | Marker-based tracking | Real time

Abstract: The PERVIVAL project aims at developing an interactive system with the preliminary function of explaining a complex museum collection in a simple and immediate way and allowing the visitor to better understand the museum collection he is about to see. In particular, the interactive system aims at enhancing the understanding of the collections of funeral furnishings of Egyptians, which are characterized by a multiplicity of objects of rich symbolism and connected to each other through complex funeral rituals. The idea is to explain the religious creed of ancient Egyptians through the objects placed in the tomb, having in this way a double benefit: enlightening the rituals and placing the objects back in their primary function. In this way, the knowledge of the visitor is not only enlarged through the description of something that is described on papyruses or inscriptions (hence, not comprehensible) but also the proper function of every single object will be explained through the connection among them, as a function of amulets or goods necessary to travel through the World of the Dead. The connection between the different objects allows a much greater understanding of the exposed collection that would be perceived in this way not as a set of single isolated pieces, but as a harmonious set of complementary elements between they represent a specific historical-cultural context.

Keywords: Cultural Heritage | Dissemination | Egyptians | Exhibition | Museum | Storytelling | Virtual Reality

Abstract: With the aim to reduce the uncertainties of the traditional archaeological approach and reduce costs for ceramic investigation, in this paper a computer-based method is proposed. A discrete geometric model of a pottery fragment is the starting input, from which a first distinction in axially and not-axially symmetric surfaces can be done. Geometrical and morphological features are then recognized. Only once that all this information is obtained, it is possible to proceed with the dimensional analysis. The analysis carried on the test case here illustrated proves that the automatic method presents accuracy and robustness not achievable even using the best application of the archaeological method. This method seems to be functional to other goals, such as for pottery classification and reconstruction of ancient ceramics.

Keywords: 3D archaeology | Automatic feature recognition | Computer methods in archaeology | Surface segmentation

Abstract: In this paper, a method for determining the best choice of the 3D scanner for cultural heritage applications is presented. Generally speaking, this activity is not trivial since a 3D scanner that matches all the requirements of a typical preservation activity in cultural heritage does not exist. Thus, to the best of the authors’ knowledge, the choice of compromise is typically performed in an unstructured way. In order to structure this choice, a method based on the Analytic Hierarchy Process (AHP) is proposed. In the proposed method, the three levels of the AHP hierarchy structure are the selection of the best 3D scanner for a specific cultural heritage application (goal), the most important technical parameters that mainly affect the choice of a 3D scanner (criteria), and the devices matching the required resolution (alternatives). Having defined the goal, prioritization of the type and quality of information is performed by the team leader of the research group (typically a skilled archaeologist), while the priority of the pairwise comparison among alternatives is decided by an expert on 3D scanners. The application of the proposed method in two contrasting situations concerning pottery fragments highlights its ease of use, its robustness (confirmed by the consistency analysis), and the completeness of the technical and economic assessment (since all relevant elements are taken into account), which put together, in a structured way, competences in very different fields (archaeology and 3D digital devices).

Keywords: 3D archaeology | Analytic Hierarchy Process (AHP) | Choice of best 3D scanners

Abstract: Constant radius geometric features are a common type of manufacturing features of ancient ceramics. They are obtained by a sweeping action of a tool, which leaves negative or positive traces characterized by a cross-section with one or more constant radii. The automatic recognition and dimensional characterization of these features could be useful for understanding the technology used to manufacture ceramics. Thus, a new perspective in archaeological investigations can be furnished. For this purpose, in this paper a new computer-based methodology suited to segmenting constant radius geometric features and measuring their dimensional parameters is proposed. Starting from a 3D discrete geometric model of the ceramic, the region pertaining to these features is determined and measurements of their radii are performed. Due to the uncertainties of various sources, which affect the investigated object, the required process is not trivial. In order to solve this problem, the segmentation phase is conducted using a non-conventional logic suitable for exploring the object with a fuzzy sensitivity, and the measurement is performed by a robust fitting method applied to the segmented entities. The methodology has been tested in the identification of embossed decorations of an ancient olla. The combined effects of the feature segmentation process together with the measure detection approach on the obtained results are critically analyzed and discussed.

Keywords: Computer methods in archaeology | Fuzzy logic | Geometric features recognition | Metrology for cultural heritage

Abstract: The construction of artificial emissary of Lake Fucino's represents one of the most significant engineering challenges that took place in antiquity. Unfortunately, the imposing structure of the Roman emissary was almost completely erased from the building of the late nineteenth century, constructed for the final drying of the lake. This article presents its virtual reconstruction, to understand the technological issues met by Romans and to visually offer reconstruction theories starting from interpreting of the few Roman remains. So that, engineering resources are used to try to understand unresolved issues in archaeology.

Abstract: In this paper, a new method for axis detection of discrete thin-walled axially symmetric surfaces is presented. This method is based on the property of thin-walled axially symmetric surfaces that the minimum path of a point on the external wall to the internal wall is on a straight line passing through the axis. This working principle, since it does not require the evaluation of differential geometrical properties, makes the method robust to noise. The proposed method has been applied in a very critical application area: axially symmetric archaeological pottery fragments, for which the evaluation of the axis is complex because of manufacturing error and of modification of the surface properties due to the action of time and weather. The trueness of the proposed method is compared with those of the five methods presented in the literature in the analysis of real sherds of various dimensions and conditions. The proposed method demonstrates greater robustness than these methods and is shown to be promising to improve the number of sherds that can be successfully analyzed.

Keywords: 3D archeology | Axis estimation | Computer | Geometric inspection | Methods in archaeology

Abstract: The paper presents a virtual diving system based on a virtual reality (VR) application for the exploitation of the Underwater Cultural Heritage. The virtual diving experience has been designed to entertain users, but its added pedagogical value is explicitly emphasized too. In fact, the ludic activities, consisting in the simulation of a real diving session from the point of view of a scuba diver, are following a storyline described by a virtual diving companion who guides users during the exploration of the underwater archaeological site. The virtual diving system provides general and historical-cultural contents, but also information about the flora and fauna of the specific submerged site to the users. The results collected through user studies demonstrate that the proposed VR system is able to provide a playful learning experience, with a high emotional impact, and it has been well appreciated by a large variety of audiences, even by younger and inexperienced users.

Keywords: Serious games | Underwater archaeological sites | Underwater Cultural Heritage | Virtual diving system | Virtual reality

Abstract: The visualization and analysis of mosaics and pavements are often compromised by their large sizes, which do not enable the observer to perceive their whole arrangement or to focus on details placed in farthest areas from its boundaries. Moreover, the usual precarious state of conservation of these artefacts, often with damaged or missing areas, makes it difficult to perceive their original aesthetic value. To overcome these limitations, we propose an application of augmented reality able to support the observer in two ways: first, the application completes the missing surface of the mosaic or pavement by integrating the existent surface with a virtual reconstruction; second, it enables the analysis of the geometric pattern of the mosaic/pavement by overlaying virtual lines and geometric figures in order to explicit its geometric arrangements. The result is achieved via a custom Android application able to recognize and track the mosaic figure pattern and extra marker board, obtaining in that way a coordinate system used to render in real-time the reconstruction of the mosaic. Such rendering is overlaid to the video stream of the real scene. The application runs on a standard smartphone embedded in a Google Cardboard-compatible viewer and therefore is extremely affordable. As a case study, in order to reconstruct its aspects and to analyse its geometric pattern, we chose the roman mosaic re-found in Savignano sul Panaro (near Modena, Italy) in 2011, after 115 years from its first discovery, which is preserved less than half of its original 4.5 x 6.9 m surface.

Keywords: Augmented Reality | Cultural heritage | Geometric pattern | Photogrammetry | Real-time visualization | Roman mosaic

Abstract: This paper proposes the integration of photogrammetric reconstruction, 3D modelling and augmented reality application in order to achieve the complete visualization of a stone sculpture even if highly damaged or fragmentary. The first part of the research aims to the reconstruction of the original aspect of an incomplete sculpture, by using photogrammetry techniques based on standard resolution photos and free software in order to obtain a first model; then, we integrate this model with other 3D digital data (from other sculptures of the same period) or with 3D modelling based on historical sources and views from historians, aiming to achieve the original aspect of the sculpture. The second part of the research consists of the embedding of the obtained model in a custom application able to render in real-time the 3D reconstruction of the lion. Then, the rendering is overlaid to the video stream of the real scene and, as a result, a complete 3D digital model of the sculpture is achieved and could be visualized through a VR viewer. As a case study, we focus on a Roman stone sculpture of a male lion conserved in the Museo Estense of Modena (Italy), which lacks of its head and its four legs. The original aspect of the lion may be achieved by integrating the damaged sculpture with other photogrammetric reconstructions of lions sculptures of the same period and with 3D model based on historical sources. Finally, the lion is visualized through an augmented reality application which digitally overlays the reconstructed models on the original one.

Keywords: Augmented Reality | Cultural heritage | Photogrammetry | Real-time visualization | Virtual modeling

Abstract: The dimensional characterisation of pottery is usually necessary to typify finds and also to recognise sherds pertaining to the same object. With the aim of reducing the uncertainties that typically affect the measurement carried out by the approach traditionally performed by archaeologists, we propose a new automatic method for dimensional characterisation of pottery fragments. The method, starting from a 3D-scanned high point density model, takes advantages from the preventive segmentation and recognition of its significant geometric features; the corresponding characteristic dimensions are evaluated by dedicated procedures. The dimensions measured are also those typically evaluated by archaeologists. In order to quantify the performances of the proposed method, a comparison of its repeatability and reproducibility is made with respect to the traditional manual approach. The proposed method, tested in some real critical cases, demonstrates better performances and lower uncertainties with respect to the traditional approaches.

Keywords: 3D archaeology | Automatic feature recognition | Computer methods in archaeology | Measurement precision in archaeology | Pottery profile | Surface segmentation

Abstract: For the purpose of reducing uncertainties in the measurements of morphologically complex biological objects, the authors present a new automatic method, which takes advantage from the representation of the object in the form of the 3D geometric model obtained from CT-scans or 3D scanning. In this paper, the method is verified in real cases and compared with the traditional approaches.

Keywords: 3D biomedical image analysis | measurement accuracy | measurement protocols in biomedicine | shape segmentation

Abstract: The paper presents the application of the technologies and methods defined in the VISAS project for the case study of the underwater archaeological site of Cala Minnola located in the island of Levanzo, in the archipelago of the Aegadian Islands (Sicily, Italy). The VISAS project (http://visas-project.eu) aims to improve the responsible and sustainable exploitation of the Underwater Cultural Heritage by means the development of new methods and technologies including an innovative virtual tour of the submerged archaeological sites. In particular, the paper describes the 3D reconstruction of the underwater archaeological site of Cala Minnola and focus on the development of the virtual scene for its visualization and exploitation. The virtual dive of the underwater archaeological site allows users to live a recreational and educational experience by receiving historical, archaeological and biological information about the submerged exhibits, the flora and fauna of the place.

Keywords: Underwater 3D reconstruction | Underwater cultural heritage | Virtual exploitation | Virtual reality

Abstract: The shipment of heritage artefacts for restoration or temporary/travelling exhibition has been virtually lacking in customised packaging. Hitherto, packaging has been empirical and intuitive which has unnecessarily put the artefacts at risk. So, this research arises from the need to identify a way of designing and creating packaging for artefacts which takes into account structural criticalities to deal with deteriorating weather, special morphology, constituent materials and manufacturing techniques. The proposed methodology for semi-automatically designing packaging for heritage artefacts includes the integrated and interactive use of Reverse Engineering (RE), Finite Element Analysis (FEA) and Rapid Prototyping (RP). The methodology presented has been applied to create a customised packaging for a small C3rd BC bronze statue of Heracles (Museo Civico “F.L. Belgiorno” di Modica-Italy). This methodology has highlighted how the risk of damage to heritage artefacts can be reduced during shipping. Furthermore, this approach can identify each safety factor and the corresponding risk parameter to stipulate in the insurance policy.

Keywords: Cultural heritage | FEM | Laser scanning | Packaging | Rapid prototyping

Abstract: With the aim to improve the quality of the traditional archaeological approach and reduce costs for ceramic investigation, in this paper a computer-based method is proposed. A discrete geometric model of a pottery fragment is the starting input, from which a first distinction in axially and not-axially symmetric surfaces can be done. Geometrical and morphological features are then recognized. Only once that all these information are obtained, it is possible to proceed with the dimensional analysis. The method here proposed allows reducing the uncertainties of the traditional archaeological approach. The analysis carried on the test case here presented, proves that the automatic method presents repeatability and reproducibility that cannot be obtained even using the best application of the archaeological method. This method seems to be functional to other scopes such as for pottery classification and reconstruction of ancient ceramics.

Keywords: 3D archaeology | Automatic feature recognition | Computer methods in archaeology | Surface segmentation

Abstract: The paper presents an outcome of the VISAS project (www.visas-project.eu) that concerns a virtual reality application for the exploitation of the underwater cultural heritage. The VR system takes advantage of novel 3D reconstruction techniques to provide geolocated and multi-resolution textured 3D models of underwater archaeological sites. Within the virtual underwater sites users live a recreational and educational experience by receiving historical, archaeological and biological information and contents about the submerged exhibits and structure of the site. Furthermore, the VR system allows divers to make a detailed planning of the operations and itinerary that will be later performed in the underwater environment.

Keywords: underwater 3D reconstruction | Underwater cultural heritage | VR systems

Abstract: The underwater cultural heritage is an immeasurable archaeological and historical resource with huge, but yet largely unexploited, potentials for the maritime and coastal tourism. In this regard, in the last years, national and international government authorities are supporting and strengthening research activities and development strategies, plans and policies to realize a more sustainable, responsible and accessible exploitation of the underwater cultural heritage. To this end, the paper presents the architecture of a new system that, taking advantage of the modern virtual and augmented reality technologies, allows diver and non-diver tourists to make a more engaging and educational experience of the underwater archaeological sites. This system has been developed and tested in the VISAS project (www.visasproject. eu) that aims to the enhancement of the cultural and tourist offer related to the underwater archaeology through innovation of modes of experience, both on site and remote, of the underwater environments of archaeological interest.

Keywords: AR systems | Underwater 3D reconstruction | Underwater cultural heritage | VR systems

Abstract: Digital documentation and high-quality 3D representation are always more requested in many disciplines and areas due to the large amount of technologies and data available for fast, detailed and quick documentation. This work aims to investigate the area of medium and small sized artefacts and presents a fast and low cost acquisition system that guarantees the creation of 3D models with an high level of detail, making the digitalization of cultural heritage a simply and fast procedure. The 3D models of the artefacts are created with the photogrammetric technique Structure From Motion that makes it possible to obtain, in addition to three-dimensional models, high-definition images for a deepened study and understanding of the artefacts. For the survey of small objects (only few centimetres) it is used a macro lens and the focus stacking, a photographic technique that consists in capturing a stack of images at different focus planes for each camera pose so that is possible to obtain a final image with a higher depth of field. The acquisition with focus stacking technique has been finally validated with an acquisition with laser triangulation scanner Minolta that demonstrates the validity compatible with the allowable error in relation to the expected precision.

Keywords: Cultural heritage | Focus stacking | Photogrammetry | Small artefacts | Structure from motion

Abstract: Blind people are typically excluded from equal access to the world’s visual culture, thus being often unable to achieve concrete benefits of art education and enjoyment. This is particularly true when dealing with paintings due to their bi-dimensional nature impossible to be explored using the sense of touch. This may be partially overcome by translating paintings into tactile bas-reliefs. However, evidence from recent studies suggests that the mere tactile exploration is often not sufficient to fully understand and enjoy bas-reliefs. The integration of different sensorial stimuli proves to dramatically enrich the haptic exploration. Moreover, granting blind people the possibility of autonomously accessing and enjoying pictorial works of art, is undoubtedly a good strategy to enrich their exploration. Accordingly, the main aim of the present work is to assess the feasibility of a new system consisting of a physical bas-relief, a vision system tracking the blind user’s hands during “exploration” and an audio system providing verbal descriptions. The study, supported by preliminary tests, demonstrates the effectiveness of such an approach capable to transform a frustrating, bewildering and negative experience (i.e. the mere tactile exploration) into one that is liberating, fulfilling, stimulating and fun.

Keywords: Blind people | Cultural heritage | Hand tracking | Human-computer interaction

Abstract: Although 3D models are useful to preserve the information about historical artefacts, the potential of these digital contents are not fully accomplished until they are not used to interactively communicate their significance to non-specialists. Starting from this consideration, a new way to provide museum visitors with more information was investigated. The research is aimed at valorising and making more accessible the Egyptian funeral objects exhibited in the Sforza Castle in Milan. The results of the research will be used for the renewal of the current exhibition, at the Archaeological Museum in Milan, by making it more attractive. A 3D virtual interactive scenario regarding the "path of the dead", an important ritual in ancient Egypt, was realized to augment the experience and the comprehension of the public through interactivity. Four important artefacts were considered for this scope: Two ushabty, a wooden sarcophagus and a heart scarab. The scenario was realized by integrating low-cost Virtual Reality technologies, as the Oculus Rift DK2 and the Leap Motion controller, and implementing a specific software by using Unity. The 3D models were implemented by adding responsive points of interest in relation to important symbols or features of the artefact. This allows highlighting single parts of the artefact in order to better identify the hieroglyphs and provide their translation. The paper describes the process for optimizing the 3D models, the implementation of the interactive scenario and the results of some test that have been carried out in the lab.

Keywords: 3D modelling | Cultural Heritage | Leap Motion | Oculus Rift | Unity | Virtual Reality | Visualisation

Abstract: Mild heating devices currently available to conservators are still limited in terms of precision, versatility, mobility, accessibility and cost. Moreover, they lack a range of operational features, such as low power requirements, efficient power use, temperature stability and uniform heat distribution. Carbon nanotubebased technologies can provide a wide range of technical solutions for overcoming these limitations, thereby allowing the development of more precise, flexible and portable heating devices. This work describes the design of an innovative carbon nanotube-based intelligent mobile accurate thermo-electrical mild heating device, to be used in the art conservation field. The device consists of three different types of flexible heating mats with different designs (opaque and ultra-thin/woven and breathable/transparent) and different operational and physical properties. The entire heating system is completed by a control unit that controls, monitors and registers the heating and by a power supply unit. First tests performed on a series of prototypes of the designed heaters showed that the device was able to convey uniform heating on different working materials, thus proving to be effective for thermal consolidation. © 2014 The Author(s).

Keywords: Carbon nanotubes | Cultural heritage | Mild heating devices

Abstract: 3D reconstructions of small objects are more and more frequently employed in several disciplines such as medicine, archaeology, restoration of cultural heritage, forensics, etc. The capability of performing accurate analyses directly on a three-dimensional surface allows for a significant improvement in the accuracy of the measurements, which are otherwise performed on 2D images acquired through a microscope. In this work we present a new methodology for the 3D reconstruction of small sized objects based on a multi-view passive stereo technique applied on a sequence of macro images. The resolving power of macro lenses makes them ideal for photogrammetric applications, but the very small depth of field is their biggest limit. Our approach solves this issue by using an image fusion algorithm to extend the depth of field of the images used in the photogrammetric process. The paper aims to overcome the problems related to the use of macro lenses in photogrammetry, showing how it is possible to retrieve the camera calibration parameters of the sharp images by using an open source Structure from Motion software. Our approach has been tested on two case studies, on objects with a bounding box diagonal ranging from 13.5. mm to 41. mm. The accuracy analysis, performed on certified gauge blocks, demonstrates that the experimental setup returns a 3D model with an accuracy that can reach the 0.05% of the bounding box diagonal. © 2013 Elsevier Masson SAS.

Keywords: 3D reconstruction | Cultural heritage | Digital documentation | Image fusion | Macro lens | Small objects

Abstract: This paper describes the experimentation of a common multi-view stereo technique on a particularly complex test case: the "Via Colonnata" in the archaeological site of Kyme Eolica in Turkey. The study demonstrates that it is possible to create a detailed 3D model of an area sized tens of square meters without the need to use any dedicated device like laser scanners, drones or helium balloons, but just employing a digital camera and open source software. The reconstruction process implemented in this study addresses and solves some of the most relevant problems related to the reconstruction of large areas and the subsequent mapping of a texture on the geometrical model. In particular, we suggest some guidelines for the acquisition phase that help to reduce the subsequent problems related both to 3D geometry creation and texture mapping. In the pre-processing phase, we propose an automated technique for filtering of unimportant areas, based on the analysis of the disparity maps related to each image pair (the farther areas from the current point of view are masked out, in order to obtain a 3D model free of artifacts/defects). For the texture mapping process, in order to reduce the blur resulting from averaging and blending operations in overlapping areas, we propose a method that automatically identifies the most appropriate subset of images to be projected on the 3D model. © 2013 IEEE.

Keywords: Cultural Heritage | Multi-view stereo | texture mapping

Abstract: The contribution regards the surveying of two statues of famous contemporary sculptors that have been placed in the central zone of Cosenza, which has been transformed in an open air museum. To realize a 3-D representation of the museum, different methodologies have been used, based on classical surveying (total stations and GNSS), image data and range data. The increasing performances of the new models of Time Of Flight (T.O.F.) laser scanners allow to build accurate models also for medium-size objects; on the other hand, the recent techniques of 3D modeling enable the processing of large amount of data and the effective removal of noises. Thus, if an extreme accuracy is not required, one can think to use the T.O.F. laser scanner, also for the surveying of statues. For the acquisition of the surfaces of the statues, two different types of laser scanning have been used: the Leica Scan StationC10, based on Time Of Flight, and the Minolta VIVID 300 triangulation scanner. In the paper, the comparison between the results obtained by using the different techniques is described.

Keywords: 3D modelling | Augmented reality | City model | Cultural heritage | Laser scanning | Multiresolution | Representation

Abstract: The creation of three-dimensional virtual models by optical technologies typically involve uncontrolled metric errors, in particular, when small high-resolution 3-D imaging systems are used to reconstruct a large object. Within Cultural Heritage, the problem of metric accuracy is a major issue and no methods are currently available for controlling and enhancing it. This paper presents a methodology based on the integration of a 3D range camera system with an optical tracking technique. The basic idea is the generation of a global coordinate system determined by the optical tracker, which controls the rigid motions of the 3D range camera system during multi-scan processes. The tracking process is based on measuring the spatial coordinates of reference markers located onto the range camera. The metric reliability of the 3D model reconstruction is guaranteed to a known acceptable level. Experimental results on a Statue of Hope located at the English Cemetery in Florence, are also reported. © 2012 IEEE.

Keywords: 3D reconstruction | Cultural Heritage | optical tecquiques

Abstract: Nowadays, optical sensors are used to digitize sculptural artworks by exploiting various contactless technologies. Cultural Heritage applications may concern 3D reconstructions of sculptural shapes distinguished by small details distributed over large surfaces. These applications require robust multi-view procedures based on aligning several high resolution 3D measurements. In this paper, the integration of a 3D structured light scanner and a stereo photogrammetric sensor is proposed with the aim of reliably reconstructing large free form artworks. The structured light scanner provides high resolution range maps captured from different views. The stereo photogrammetric sensor measures the spatial location of each view by tracking a marker frame integral to the optical scanner. This procedure allows the computation of the rotation-translation matrix to transpose the range maps from local view coordinate systems to a unique global reference system defined by the stereo photogrammetric sensor. The artwork reconstructions can be further augmented by referring metadata related to restoration processes. In this paper, a methodology has been developed to map metadata to 3D models by capturing spatial references using a passive stereo-photogrammetric sensor. The multi-sensor framework has been experienced through the 3D reconstruction of a Statue of Hope located at the English Cemetery in Florence. This sculptural artwork has been a severe test due to the non-cooperative environment and the complex shape features distributed over a large surface. © 2012 by the authors; licensee MDPI, Basel, Switzerland.

Keywords: 3D imaging sensors | 3D reference information system | Cultural heritage | Stereo-photogrammetry | Structured light scanning

Abstract: The diagnostic analysis of decay processes on small specimens is gaining importance in the restoration and maintenance of archeological finds. In this context, the 3D reconstruction is very useful for the study and identification of the different types of decay. In this paper we present the analysis conducted on two small specimens taken from an ancient underwater pavement, using a new technique for the 3D reconstruction of small sized objects based on a multi-view passive stereo technique applied on a sequence of macro images. In order to overcome the problems related to the use of macro lenses, such as the very small depth of field and the loss of sharpness due to diffraction, each image of the sequence is obtained by merging a stack of images acquired at different focus planes by the means of an image fusion algorithm. The experimentation involves a series of preliminary laboratory tests in which we validate the system accuracy and the 3D reconstruction of specimens taken from a marble pavement located in the underwater archeological site park of Baiae (Naples, Italy). The results show that with our approach it is possible to obtain high quality textured 3D models of objects with dimensions ranging from few millimeters to few centimeters, which can be usable both for interactive measurements and virtual presentations. © 2012 IEEE.

Keywords: 3D reconstruction | Cultural Heritage | Image Fusion | Macro Lens | Small Objects

Abstract: In this contribution we describe the modern 2D and 3D technologies for the documentation, analysis and restoration of paintings. RGB color imaging, IR and UV fluorescence sensors, together with highly precise active sensors are among the most widely technologies in this field. The devices provide information on the painting's materials, on the employed technique and on the conservation's state of the art work. However, all information must be correctly registered to be able to draw safe conclusions and perform the most adequate conservation interventions. We also present a complete example where multispectral visible images, IR refiectography, UV fluorescence and 3D data are acquired and then combined, showing how the integration gives a new and significant improvement in the analysis of painting. © 2007 SPIE-IS&T.

Keywords: 3D sensing | Cultural heritage | Image registration | Multispectral imaging | Reflectography

Abstract: Italy has plenty of cultural heritages. The masterpieces are often placed in locations which are difficult to reach, moreover many artifacts, coming from man's creativity, have very complex functioning. The authors of this paper describe their experience in using the computer graphics capabilities in order to reproduce four ancient clocks functioning coming from different Italian regions. The study is based not only on the 3D-shapes reconstruction but also on the simulation of their complex mechanisms in order to mimic their functioning. The realism of the reconstruction allows to use the graphical products in exhibits, museums and also for maintenance programs. The rendering techniques together with an accurate camera path, allow to get into the clock mechanisms and to appreciate all the features (and even secrets) that a simple glance cannot reveal. Copyright © 2006 John Wiley & Sons, Ltd.

Keywords: Ancient clock | Computer-aided simulation | Cultural heritage | Virtual museum