3D technologies for cultural heritages

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

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

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

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

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

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

The “San Pietro al Monte Abbey project: a virtual tour for everyone” consists in the construction of a high-tech station that allows visitors with mobility limitations to be virtually accompanied by a guide to the Benedictine abbey of San Pietro al Monte along the ancient access route that can only be reached on foot with trekking equipment. The room with the virtual instrumentation is located in the Casa del Pellegrino in Civate (Lecco, Italy). It is a museum structure-based located in a media reception building. From its entrance, it is possible to see the final destination. The virtual tour preserves the dialogue between the environment, the monument, and the ‘virtual pilgrim'. By also acting as an information database, it enhances the use of the basilica of San Pietro al Monte even for visitors equipped with tablets who reach the building on foot. The virtual tour application has been developed with Unity3D. The interactive application has different virtual scenes with photos, 360 ∘ videos, an external digital twin of the abbey, and some interesting internal digital twins of the most important monuments inside the abbey.

Keywords: Digital twin , Photogrammetry , Virtual tour

At Annone di Brianza (Italy) in the Church of St. George, it is possible to admire the “ANCONA DELLA PASSIONE" (altarpiece of the Passion), an altarpiece painted and gilded carved wood cabinets. The great altarpiece adorned the right side chapel of Saint John the Baptist, whose construction dates back to the first half of the century XVI at the behest of Annoni, one of the most authoritative families of Milan of the sixteenth and seventeenth century. Since 2019 the altarpiece has been protected inside a special room in order to avoid damage caused by the temperature and humidity. Access to this room is not allowed to people who visited the church. In order to allow the user to admire and explore each minimal detail of the polyptych altarpiece a totem has been designed and it's located just outside of the special room. The totem in fact is composed of a 32 in. touch screen with a PC embedded and the Virtual tour application. The Virtual tour application has been developed with Unity3D. The interactive application has different virtual scenes with photos, videos, an external digital twin of the polyptych with both, open and closed doors.

Keywords: Digital twin , Inclusive tour , Photogrammetry , Virtual tour , Visual impairment users

The paper presents the development of a Virtual Reality application to perform dives in the Christoforos Shipwreck. The huge wreck lies in the Panormos Bay of the Skopelos island (Greece) at a depth of 45 meters. Based on a well-known methodology designed for ancient shipwrecks, the 3D reconstruction of the underwater site has been carried out by adjusting the workflow to survey modern shipwrecks. In particular, the methodology, based on photogrammetry, is capable to provide a highly detailed 3D reconstruction of the shipwreck in few dives, considering issues like working depth, elevations, and thin elements modelling. Moreover, the paper describes the optimization of the 3D model and the software to be executed in low-performance HMD devices. The resulting Virtual Reality (VR) application, realized for touristic purposes, recreates the exact ambient conditions inside and outside the water simulating the flora and fauna of the place, the coastline, allowing users to live a recreational and educational experience by virtual diving in the underwater site.

Keywords: 3D modeling , History , Image reconstruction , Ships , Three dimensional computer graphics

Ceramics classification and reconstruction are fundamental for the knowledge of history, economy, and art of a site. The method traditionally used by archeologists for their investigation presents a series of significant limitations. The results depend on subjectivity, specialization, personal skills, and professional experience of the operator; hence, they are not reproducible and repeatable. Furthermore, since the method is time-consuming, it is used to analyze only indicative samples that have characteristic components. In order to overcome these limitations, in the last years, some automatic methods for studying ancient pottery's findings are proposed in literature. All the most promising ones analyze a 3D discrete geometric model of ceramics. By analyzing the voluminous related literature, the hottest topics are 3D geometric model setup, virtual prototyping, geometric model fragment processing, geometric model processing of whole-shape pottery, 3D puzzling of archeological fragments, classification, and additive manufacturing technologies for physical reconstruction of ceramics. In order to help all the researchers involved in this field, this chapter aims to provide a comprehensive and critical analysis of the state of the art for the abovementioned topics. For this purpose, the present review is focused on the presentation of the pros and cons of the techniques used on these different issues.

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

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

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

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

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

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

For the past few decades, topology optimization (TO) has been used as a structural design optimization tool. With the passage of time, this kind of usage of TO has been extended to many application fields and branches, thanks to a better understanding of how manufacturing constraints can achieve a practical design solution. In addition, the advent of additive manufacturing and its subsequent advancements have further increased the applications of TO, raising the chance of competitive manufacturing. Design for additive manufacturing has also promoted the adoption of TO as a concept design tool of structural components. Nevertheless, the most frequent applications are related to lightweight design with or without design for assembly. A general approach to integrate TO in concept designs is still missing. This paper aims to close this gap by proposing guidelines to translate design requirements into TO inputs and to include topology and structural concerns at the early stage of design activity. Guidelines have been applied for the concept design of an inner supporting frame of an ancient bronze statue, with several constraints related to different general design requirements, i.e., lightweight design, minimum displacement, and protection of the statue's structural weak zones to preserve its structural integrity. Starting from the critical analysis of the list of requirements, a set of concepts is defined through the application of TO with different set-ups (loads, boundary conditions, design and non-design space) and ranked by the main requirements. Finally, a validation of the proposed approach is discussed comparing the achieved results with the ones carried out through a standard iterative concept design.

Keywords: Design methodology , Lightweight design , Restoration of ancient statues , Topology optimization

The dynamical behaviour of the Bronze Age war chariots was studied, considering the different assembly solutions that were found in evidences and pictures. In particular, the chariots with the axle in rear position, typical of Near-East and Egypt, were compared with the European ones, which generally had the axle in central position under the chariot cockpit. Furthermore, the role of the floor, usually realized in woven leather or other organic fibres, was investigated. Dynamical finite element and multibody simulation software was used for studying the behaviour of the chariots in occasional overloading events, such as bumps or curves. An experimental device was set up for studying the difference of the response of a woven floor with respect to a wooden one. Finally, a finite element frequency response analysis was carried out to investigate the behaviour in full run over a rough ground. The results showed that position of the axle did not significantly influence the response of the chariot to occasional overloads. On the contrary, it had a strong influence on the stability of the passengers: rear axle chariots were much more effective in cutting the vibrations transmitted to the passengers when running at high speed. This effect was amplified by an increased floor flexibility, which was achieved with a woven floor. These findings could explain the diffusion of the rear-axle chariots in the Near-East and Egypt, where the chariotry was the most important part of the armies: indeed, the effectiveness in cutting the vibrations at high speed should be a crucial factor for ensuring the required precision to the transported archers. On the contrary, the likely marginal role of the chariots in the European armies could lead to the diffusion of central axle model, which ensured a lower burden on the draught horses.

Keywords: Bronze age , Chariots , Dynamics , Stability , Vibrations , War

This article reports the results of a research aimed to evaluate the ability of a haptic interface to improve the user experience (UX) with virtual museum systems. In particular, two user studies have been carried out to (1) compare the experience aroused during the manipulation of a 3D printed replica of an artifact with a pen-like stylus with that aroused during the interaction (visual and tactile) with a 3D rendering application using a haptic interface and PC monitor, and (2) compare the users' perceived usability and UX among a traditional mouse-based desktop interface, haptic interface, and haptic gamified interface based on the SUS scale and the AttrakDiff2 questionnaire. A total of 65 people were involved. The considered haptic application is based on the haptic device Omega 6 produced by Force Dimension, and it is a permanent attraction of the Museo Archeologico Nazionale delle Marche. Results suggest that the proposed haptic interface is suitable for people who commonly use mouse-based computer interaction, but without previous experience with haptic systems, and provide some insights useful to better understand the role of haptic feedback and gamification in enhancing UX with virtual museums, and to guide the development of other similar applications in the future.

Keywords: haptic interface , user experience , Virtual museum , virtual reality

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

The detection of the symmetry axis from discrete axially symmetric surfaces is an interesting topic, which is transversal to various fields: from geometric inspection to reverse engineering, archeology, etc. In the literature, several approaches have been proposed for estimating the axis from high-density triangular models of surfaces acquired by three-dimensional (3D) scanning. The axis evaluation from discrete models is, in fact, a very complex task to accomplish, due to several factors that inevitably influence the quality of the estimation and the accuracy of the measurements and evaluations depending on it. The underlying principle of each one of these approaches takes advantage of a specific property of axially symmetric surfaces. No investigations, however, have been carried out so far in order to support in the selection of the most suitable algorithms for applications aimed at automatic geometric inspection. In this regard, ISO standards currently do not provide indications on how to perform the axis detection in the case of generic axially symmetric surfaces, limiting themselves to addressing the issue only in the case of cylindrical or conical surfaces. This paper first provides an overview of the approaches that can be used for geometric inspection purposes; then, it applies them to various case studies involving one or more generic axially symmetric surfaces, functionally important and for which the axis must be detected since necessary for geometric inspection. The aim is to compare, therefore, the performances of the various methodologies by trying to highlight the circumstances in which these ones may fail. Since this investigation requires a reference (i.e. the knowledge of the true axis), the methodologies have been applied to discrete models suitably extracted from CAD surfaces.

Keywords: axially symmetric surfaces , Axis of symmetry , geometric inspection , geometrical dimensioning and tolerancing , high-density triangular models