Virtual Restoration and Virtual Reconstruction in Cultural Heritage: Terminology, Methodologies, Visual Representation Techniques and Cognitive Models
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information Article Virtual Restoration and Virtual Reconstruction in Cultural Heritage: Terminology, Methodologies, Visual Representation Techniques and Cognitive Models Eva Pietroni * and Daniele Ferdani CNR, Institute of Heritage Science, Research Area Rome 1, Via Salaria Km 29,300, Monterotondo St., 00015 Rome, Italy; [email protected] * Correspondence: [email protected]; Tel.: +39-06-9067-2721 Abstract: Today, the practice of making digital replicas of artworks and restoring and recontex- tualizing them within artificial simulations is widespread in the virtual heritage domain. Virtual reconstructions have achieved results of great realistic and aesthetic impact. Alongside the practice, a growing methodological awareness has developed of the extent to which, and how, it is permissible to virtually operate in the field of restoration, avoid a false sense of reality, and preserve the reliability of the original content. However, there is not yet a full sharing of meanings in virtual restoration and reconstruction domains. Therefore, this article aims to clarify and define concepts, functions, fields of application, and methodologies. The goal of virtual heritage is not only producing digital replicas. In the absence of materiality, what emerges as a fundamental value are the interaction processes, the semantic values that can be attributed to the model itself. The cognitive process originates from this interaction. The theoretical discussion is supported by exemplar case studies carried out by the authors over almost twenty years. Finally, the concepts of uniqueness and authenticity need Citation: Pietroni, E.; Ferdani, D. Virtual Restoration and Virtual to be again pondered in light of the digital era. Indeed, real and virtual should be considered as a Reconstruction in Cultural Heritage: continuum, as they exchange information favoring new processes of interaction and critical thinking. Terminology, Methodologies, Visual Representation Techniques and Keywords: virtual restoration; virtual reconstruction; reliability; authenticity; interaction; virtual Cognitive Models. Information 2021, heritage; virtual museum; cognitive processes in cultural heritage 12, 167. https://doi.org/10.3390/ info12040167 Academic Editor: Juan Carlos Torres 1. Introduction 1.1. Cybernetic Approach to Virtual Heritage Received: 27 February 2021 A digital “object” can be a text message, a 2D image, a 3D model, a movie, or a sound. Accepted: 6 April 2021 Published: 13 April 2021 It can be a reproduction of a physical artefact, or it can be natively digital. The digital object, if limited to the reproduction of a real object, becomes a replica, if it is obtained Publisher’s Note: MDPI stays neutral through criteria and methodologies that guarantee fidelity and accuracy both at the topo- with regard to jurisdictional claims in logical/metric level and at the surface properties level. In this sense, the digital replica published maps and institutional affil- becomes a transmitter of information and allows the preservation of the knowledge of that iations. object, even if the real original is lost. Moreover, through rapid prototyping techniques, it is possible to print digital replicas and obtain physical copies that can be touched or relocated in their original context to restore a fragmented or lost cultural object. Physical copies can also be used for haptic experiences addressed to the public, which is in particular useful to enhance accessibility for visually impaired persons (if following specific criteria and Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. characterized by a recognisable tactile pattern). This article is an open access article However, the digital “content” should not be limited to the reproduction of an object. distributed under the terms and It should be a communicative and cognitive unity, endowed with form and meaning. conditions of the Creative Commons According to the cybernetic approach introduced by Gregory Bateson [1], the main Attribution (CC BY) license (https:// objective of virtual heritage is not the massive digital recording, the model, or its objec- creativecommons.org/licenses/by/ tivity and description, but is the creation of a dynamic space of relations and interactions. 4.0/). Therefore, what really matters is the process, the experience, what we do with the digital Information 2021, 12, 167. https://doi.org/10.3390/info12040167 https://www.mdpi.com/journal/information Information 2021, 12, 167 2 of 30 model, and the simulation of a multiple past open to many possible experiences. The feedback obtained from the virtual context modifies our behavior and critical thinking and stimulates understanding and attribution of meaning; thus, the process of knowledge is built and consolidated [2]. Hence, the goal of a virtual process is to increase perceptual and cognitive levels, reactivating spatial–temporal relationships and meanings of the cultural object. The virtual dimension facilitates the mental process of imagination [3], giving shape to an abstract concept (a vanished ancient context cannot be perceived and experienced), making legible and recognizable what the visitor is often unable to “decode”, identify, and contextualize. Virtual heritage therefore requires connection. All the information about an artefact and its context must be connected according to relational maps and accessed through experiential spaces. Typically, but not necessarily, this is a three-dimensional space. The three-dimensional space amplifies our possibilities of interaction: it allows us to explore, move, and change the point of view; to construct and to deconstruct the model according to new relational hypotheses; and to create simulations, strengthening the possibilities of analysis and interpretation. In virtual space, the cognitive activity is “embodied” [4]. This means that it should affect the user on two levels: (1) perceptual motor (sensory perception of form and affordances stimulated by the cognitive activity itself) [5] and (2) symbolic reconstruction of the meaning, thus associating deeper levels of understanding with the visible appearance. The latter can be integrations of the artefact (virtual restoration), contex- tualization in the original place (virtual reconstruction), relationship with the environment, or values and meanings attributed to the artefact by the various societies with which it entered into relation over time [6]. On this theoretical background, we are going to discuss concepts and methodologies dealing with virtual restoration and virtual reconstruction. 1.2. Definition and Domain 1.2.1. Physical Restoration In the book “Theory of Restoration”, a landmark theoretical essay of Cesare Brandi [7], which had a great influence on the Italian and international practice of restoration (at least in western countries), the author stated that: “restoration is the methodological moment of recognition of the work of art in its aesthetic and historic dual polarity, in view of its transmission to the future” [8]. In 1964, the “Venice Charter” was drafted at the Second International Congress of Architects and Technicians of Historic Monuments. The charter consists of 16 articles and defines the principles of the methodology of architectural restoration, which can be considered immutable. Here, the restoration is defined as a “a highly specialized operation. Its aim is to preserve and reveal the aesthetic and historic value of the monument and is based on respect for original material and authentic documents. It must stop at the point where conjecture begins, and in this case any extra work which is indispensable must be distinct from the architectural composition and must bear a contemporary stamp. The restoration in any case must be preceded and followed by an archaeological and historical study of the monument” [9]. Currently, modern restoration consists of eliminating the causes of deterioration and recovering the legibility of the historical evolution of an artwork [10] (p. 27). It is based on a historical– critical approach and implemented through a complete fusion of historical and technical– scientific expertise [11]. The principles developed over years, concerning the material consistency of an artwork, are currently established as international fundamentals for any restoration activity, and can be listed in the following five issues [12]: 1. Respect for aesthetic and historical value: The meaning, history, and authenticity of the cultural asset should be preserved. 2. Compatibility: It is necessary to know the material of which the cultural assets are made for a correct evaluation of the intervention and compatible materials to be used. 3. Recognition of intervention: It concerns the legibility of the original parts. Integrations should be recognizable. Information 2021, 12, 167 3 of 30 4. Reversibility: Any material used in restoration should be removable in order to return the artwork to its original conditions, allowing for future restoration. 5. Minimal intervention: It is necessary to repair or conserve original parts rather than replace materials to maintain the historical value. 1.2.2. Virtual Restoration In 1994, the professor Gianfranco Fiaccadori used the term virtual restoration as a methodology that combines technique and purpose to intervene in damaged heritage in a virtual way [13] (p. 16). More recently, the Principles of Seville, which are mainly oriented around computer-based visualization in archaeological heritage, define virtual restoration as the process of “using