Digital fabrication of cultural heritage artwork replicas. In the search for resilience and socio-cultural commitment

https://doi.org/10.1016/j.daach.2019.e00125Get rights and content

Highlights

  • Interpretive centres foster deep learning and social cohesion.

  • Digital fabrication proves that far surpasses traditional methods when replicating cultural heritage assets.

  • 3D digitization guarantees the resilience of the Antiquity.

Abstract

The traditional approach for physical reproduction in Cultural Heritage requires the production of moulds on the very surface of the original artwork in an invasive, manual and usually time-consuming process that is intensely influenced by the complexity of the piece to be reproduced. The difficulties increase when changing the size of the copy is needed. But producing replicas is a necessity, mostly when it comes to mounting exhibitions within interpretive centres. The educational role of such institutions is beyond doubt. Furthermore, they have also become major drivers of social inclusion of at-risk groups. So, having perfect copies of archaeological remains without damaging them is a challenge that technology has been facing for the last years. This paper describes a procedure to obtain exact replicas of classical statues that reduces their manipulation, thus preventing them for further damages, which was applied to two Roman marble sculptures of Medellín (Badajoz, Spain).

Introduction

The use of 3D technologies for digitizing cultural heritage has been developing rapidly and constantly in the last years, thanks in part to computer vision advances and to the improvement of technological devices. In this respect, the acquisition and storage of sites, monuments and works of art data can be carried out in a more effective and efficient way. This fact has provoked the arisen of repositories of 3D models with research purposes as well as virtual museums that have widened the applicability of these models.

The availability of an accurate digital representation opens up a broad spectrum of possibilities for experts(Katz and Tokovinine, 2017). Therefore, there have been a lot of works in this field lately, either using photogrammetry techniques or active 3D scanning (3D laser scanning, structured light 3D scanner, phase shift and time of flight laser scanners …). One can distinguish between those works dedicated to scanning open spaces and monuments (e.g. Arav et al., 2016; Sapirstein, 2016; Xu et al., 2017; Zhang et al., 2017; Balsa-Barreiro and Fritsch, 2018; Pérez et al., 2019); and those which are focused on a smaller-scaled research: artefacts (Banterle et al., 2017; Graciano et al., 2017; Banducci et al., 2018; Zhang et al., 2018), epigraphy (for instance, Ramírez et al., 2017; Di Paola and Inzerillo, 2018; Carrero-Pazos and Espinosa-Espinosa, 2018; Andreu and Serrano, 2019), sculpture (Adán et al., 2012; Zhang et al., 2015; Malik and Guidi, 2018; Perez et al., 2018), etc.

3D models in cultural heritage can be used not only for documentation and visualization purposes but also as tools for carrying out several tasks. Among them, it is worth noting the manufacture of original artworks copies (Scopigno et al., 2011; Katz and Tokovinine, 2017). Digital manufacturing, defined as the physical reproduction of objects from their three-dimensional models, combines conventional manufacturing techniques with digital technology (Ribeiro da Silva et al., 2019). It has developed rapidly in recent years, as techniques, technology and materials have evolved (Bogue, 2013), and its scope of application has not ceased to grow. Thus, its use has been extended to the most diverse areas of daily life. Cultural heritage is one of the fields in which digital manufacturing is gaining more prestige. Within this branch, its uses are multiple and very diverse (for example, the reproduction of sculptures for sensorial exhibitions, manufacturing pieces to facilitate the labour of restorers, or a more general use: allowing the resilience of the patrimony assets throughout the years) (Scopigno et al., 2017).

The digital fabrication techniques can be classified into two groups: on the one hand, the subtractive techniques that consist of carving a block by removing material to sculpt the desired piece, which is made by using a milling tool controlled by a computer. On the other hand, you can find the additive processes. As their name suggests, they consist of the deposition/addition of successive layers of material to “build” the object. These are the most spread techniques for 3D printing in the last years since they are more versatile, easy-to-use and less expensive than the others. A recent review of this type of manufacturing procedures (materials, methods, applications and challenges) can be found in Ngo et al. (2018).

The decision to opt for one type of technique or another will depend on the type and size of the piece to be replicated, the accuracy required, the material to be used, the subsequent use of the copy, etc. Up to the apparition of 3D digitization techniques (and even nowadays), it was usual to make a mould on the very surface of the sculpture when replicating it, what implies the use of products that usually affected the epidermis of the material. It is needless to say that this technique, which can go back to the Roman time (Rigdway, 1984; Gazda, 1995), also exposes the archaeological remains to unacceptable physical risks. However, having perfect replicas of artworks has been always necessary. In previous epochs, they facilitated that artists, students and common people approached to the masterpieces of the ancient world. Nowadays, they become an essential resource for culture and education.

Replicating archaeological objects with a higher standard of perfection is especially important in the case of interpretive centres. An interpretive centre is a hybrid concept between a museum and a visitors’ centre: they are thought to welcome, look after and guide visitors while introducing them in the knowledge of heritage through a museographic discourse with a pedagogical purpose (Martín Piñol, 2013). Its aim is not to acquire, study or keep heritage pieces and goods, but to show how to appreciate and take care of them in an educational manner. The absence of original pieces, which must be necessarily preserved within a museum, is palliated by the exhibition of replicas to build a narrative and iconographic discourse that must be understandable and attractive at the same time (Izquierdo et al., 2005).

Digital manufacturing becomes the ideal resource for generating the replicas needed in interpretative centres, since it provides with an efficient, accurate and quick working way that is also respectful with the original pieces as it does not require any contact. Besides, the reproduction costs have steadily decreased, favoured by the constant development of devices and technology. Two very interesting surveys on this subject are (Scopigno et al., 2011) and (Weigert et al., 2019).

The aim of this paper is to emphasise the importance of producing perfect physical reproductions of statues to provide interpretive centres with the resources needed for their educational purpose. To do this, we will analyse the work done on two Roman sculptures made of marble that were found in Extremadura (Spain). Both statues were uncovered in the excavations held under the supervision of P. Mateos (Mateos and Picado, 2011), in the hyposcaenium of the Roman theatre of Medellín (Badajoz), the ancient colony Metellinum, in Lusitania (Hispania) in mid-2007.

The rest of this paper is organised as follows. In Section 2, the archaeological study of the pieces that states the importance of the statues and the circumstances that led to the need to get high-quality replicas in a short period of time are exposed. Section 3 presents an overview of the procedure followed to obtain the 3D models. Section 4 offers a brief state of the art on digital fabrication technologies and shows how the physical reproductions were made in this case. In Section 5, the results obtained are shown and discussed. Section 6 states the conclusions.

Section snippets

Description of the statues

The largest piece is a freestanding sculpture bigger than life size (H: 167 cm; W: 64 cm; D: 36 cm) (Fig. 1. Left). Made in grey veined marble, it represents a woman who adopts an erected and frontal position, leaning on her left leg while the right, which wouldn’t support any weight, is marked under the tissue of her clothing. She elevates her right arm and her hand would be extended outwards, whereas the left one, attached to the side, is bent at the elbow to be projected forward. Both

Generation of the 3D models

Our 3D digitization method followed the stages of the 3D modelling process (Bernardini and Rushmeier, 2002). Taking into account that in this case the stream for the texture is not needed, since the statues were going to be reproduced in a marble-like material, the conceptual map proposed in (Merchán et al., 2011) could be modified to the one shown in Fig. 2. As seen, the initial stage consists of data acquisition, either using photogrammetry techniques or 3D laser scanning, depending on the

Production of the replicas

As said previously, the methods for digital manufacturing of replicas can be classified into two groups depending on the technique they utilized: subtractive or additive (Scopigno et al., 2017).

Within the first group, Computer Numerical Control (CNC) machine tools employ a spindle to remove material of the original block to obtain the replica. When a perfect copy of complex sculptures is needed, as in the case proposed, 6-axis CNC or 6 DOF robots are the most common method (La Pensée et al.,

Results

There are two immediate results that can be highlighted in the accomplishment of this work: 1) the obtaining of the physical replicas themselves and 2) the digital models that are left, that can be used by the researchers for further study.

In regard to the first result, it has been proven that digital fabrication is the most suitable option nowadays, mostly when the main challenge that has to be faced is the optimization of time and the quality of the results. In the process of digital

Discussion

Possibly, the most relevant result that can be outlined through this case study is that both the 3D digital models and the physical replicas are perfect tools for education and social cohesion. On the one hand, in concern to the digital models, they are powerful resources for formal and informal learning. The use of 3D models of monuments, sculptures, artefacts …, either directly shown on a screen or through Virtual Reality recreations, allows building educational environments in an attempt of

Conclusions

During the last years, several papers have hypothesized about the advantages and disadvantages of using one of the different technologies available for the acquisition of 3D information and its subsequent physical reproduction. But only through the experience provided by particular case studies it will be possible to come up with useful and reliable conclusions for researchers.

In this paper, we have analysed a specific case: the physical reproduction of two Roman female sculptures using laser

Declaration of competing interest

The authors declare that they have no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

References (48)

  • Y. Zhang et al.

    A multi feature fusion method for reassembly of 3D cultural heritage artifacts panel

    J. Cult. Herit.

    (2018)
  • T. Alderighi et al.

    Metamolds: computational design of silicone molds

    ACM Trans. Graph.

    (2018)
  • G. Alemanno et al.

    Interlocking pieces for printing tangible Cultural Heritage replicas. EUROGRAPHICS Work

    Graph. Cult. Herit.

    (2014)
  • J. Andreu et al.

    Contributions of the digital photogrammetry and 3D modelling of Roman inscriptions to the reading of damaged tituli: an example from the Hispania Tarraconensis (Castiliscar, Saragossa)

    Digit. Appli. Archaeol. Cult. Herit..

    (2019)
  • L.M. Banducci et al.

    Measuring usewear on black gloss pottery from Rome through 3D surface analysis

    Internet Archaeol.

    (2018)
  • F. Banterle et al.

    VASESKETCH: automatic 3D representation of pottery from paper catalog drawings

  • F. Bernardini et al.

    The 3D model acquisition pipeline

    Comput. Graph. Forum

    (2002)
  • R. Bogue

    3D printing: the dawn of a new era in manufacturing?

    Assemb. Autom.

    (2013)
  • M. Carrero-Pazos et al.

    Tailoring 3D modelling techniques for epigraphic texts restitution. Case studies in deteriorated roman inscriptions

    Digit. Appli. Archaeol. Cult. Herit.

    (2018)
  • F. Di Paola et al.

    3D reconstruction-reverse engineering-digital fabrication of the Egyptian palermo stone using by smartphone and light structured scanner

    Int. Arch. Photogramm. Remote Sens. Spat. Inf. Sci.

    (2018)
  • S. Fernando

    The culture of crafting: exploring the relationship between the hand and the machine in digital stone sculpture

  • E.K. Gazda

    Roman sculpture and the Ethos of emulation: reconsidering repetition

  • A. Graciano et al.

    Digitization of religious artifacts with a structured light scanner

    Virtual Archaeol. Rev.

    (2017)
  • J. Hayes et al.

    Digitally-assisted stone carving of a relief sculpture for the parliament buildings national historic site of Canada

    Int. Arch. Photogramm. Remote Sens. Spat. Inf. Sci.

    (2015)
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