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A shared commitment to standardising the process of hypothetically reconstructing lost buildings from the past has characterised academic research in recent years and can manifest at various stages of the reconstructive process and with different perspectives. This research specifically aims to establish a user-independent and traceable procedure that can be applied at the end of the reconstructive process to quantify the average level of uncertainty of 3D digital architectural models. The procedure consists of applying a set of mathematical formulas based on numerical values retrievable from a given scale of uncertainty and developed to simplify reuse and improve transparency in reconstructive 3D models. This effort to assess uncertainty in the most user-independent way possible will contribute to producing 3D models that are more comparable to each other and more transparent for academic researchers, professionals, and laypersons who wish to reuse them. Being able to calculate a univocal numerical value that gives information on the global average uncertainty of a certain reconstructive model is an additional synthetic way, together with the more visual false-colour scale of uncertainty, to help disseminate the work in a clear and transmissible way. However, since the hypothetical reconstructive process is a process based on personal interpretation, which inevitably requires a certain level of subjectivity, it is crucial to define a methodology to assess and communicate this subjectivity in a user-independent and reproducible way.

This paper presents preliminary findings from the ongoing Erasmus+ European project CoVHer, which focuses on the hypothetical virtual reconstructions of lost or unbuilt architecture. This contribution provides a critical assessment of the terminology specific to this field. A significant challenge lies in the absence of standardised terminology for many foundational aspects, which can lead to misconceptions and misunderstandings. The research begins with a comprehensive review of the relevant literature in the field, aiming to identify which terms are most widely accepted and appropriate to use and which are ambiguous or should be avoided. For concepts that lack a clear definition, new terminology is proposed. This paper analyses six key terms: reconstruction, uncertainty, raw model, informative model, digital representation methods, and 3D modelling techniques.

For the hypothetical reconstruction of architectural heritage, there are still no scientific standards of reference concerning their sharing and documentation. Recent international initiatives established the basis to address this problem; however, still, much work needs to be done in order to systematise good practices for the process of reconstruction and its dissemination. This contribution aims to take a step forward in the analysis and visualisation of uncertainty. Some authors have suggested various approaches to visualise uncertainty for single buildings; however, case studies at the urban scale are rarely investigated. This research proposes an improved source-based multi-feature approach aimed at analysing and visualising (through false-colour shading) the uncertainty of hypothetical 3D digital models of urban areas. The assessment of uncertainty is also quantified qualitatively by using newly defined formulas which calculate the average uncertainty weighted on the volume of the 3D model. This methodology aims to improve the objectiveness, unambiguity, transparency, reusability, and readability of hypothetical reconstructive 3D models, and its use is exemplified in the case study of the hypothetical reconstruction of Piazza delle Erbe in Verona, a project presented in the form of a docufilm at EXPO 2015 in Milan.

En el ámbito museístico es frecuente encontrarse con limitaciones logísticas que dificultan la documentación de las obras de arte. El patrimonio pictórico presenta además otras criticidades debidas a la imposibilidad de modificar la iluminación: basada en criterios de conservación y comunicación, haciendo resaltar las características materiales, cromáticas y de ejecución. Esto conduce a situaciones inadecuadas para el levantamientos por imágenes fotográficas, ya complicadas en sí por las complejas propiedades ópticas de los materiales. La técnica que aquí se presenta fue desarrollada para la documentación de la Anunciación (1430-32) de Fra Giovanni Angelico (Museo de la Basílica S. Maria delle Grazie, San Giovanni Valdarno, Arezzo) y permite eliminar y atenuar fenómenos indeseables debidos a las condiciones específicas del contexto museístico. Se mostrará una estrategia capaz de eliminar las sombras nitidas, así como los fenómenos de claroscuro, de las texturas asociadas al modelo digital de la pintura y su marco, garantizando su fidelidad visual.

This paper introduces a discussion on the visualization tools for digital replicas of objects belonging to the domains of historic architecture, archaeology, and art museum institutions. Covering a range of artifacts, from ancient drawings to manuscripts, to paintings, to objects in museums’ collections, the discussion spans from levels of iconicity related to 3D models to their presentation and visualization media. Authors introduce some established experiences, inferred from real case studies showcased during real exhibitions, to show how digital artifacts can replicate existing objects for specific purposes, with high levels of iconicity. The paper traces approaches in 3D model visualization, utilizing technologies such as Real-Time Rendering (RTR) and Virtual Reality frameworks. After a methodical acquisition of artworks to be replicated, the digital models are targeted to various stakeholders with interests in historical and artistic research, curation of museum exhibition, art restoration, or simple tourism visits. The way through which the artwork can be visualized, presenting different features each time, depends on their needs, from guided navigation of 3D models on laptop screens accompanied by explanatory texts, to free visualization through gestures on interactive high-definition touch screens. By employing high-resolution replicas mapped with gigapixel textures, even the minutest details can be observed. This approach virtually places the artwork in the hands of the users, allowing them to appreciate its characteristics at a very high level of iconicity, also enhancing the narrative potential of digital replicas in museum exhibitions.DOI: https://doi.org/10.20365/disegnarecon.32.2024.1

This contribution to the literature presents an in-depth analysis of the scene drawn by Leonardo da Vinci in the preparatory drawing, Adoration of the Magi, dated 1481, that is now housed at the Département des Arts Graphiques du Musée du Louvre in Paris, France. This analysis focuses on the architectural elements and highlights how the drawing discloses three distinct vanishing points/centers of vision: one for the classical architecture to the left of the scene, one for the Nativity hut, and one for the structure with stairs. If we consider the structures as belonging to the same 2D projected space, at least two must be depicted out of square; conversely, if we consider them as straight, standard structures, they cannot belong to the same 2D projected space. Given this assumption, we propose, on the one hand, some variations of the scene where the structures are straightened and projected according to only one of the viewpoints at a time; on the other hand, a set of variants of the scene are presented, considering the out-of-square structures. The scenes are generated by applying inverse perspective projections. These results prompt a discussion on possible reasons why Leonardo made these conscious or unconscious “formal errors”.

Among many other themes, Leonardo da Vinci’s Manuscript B contains several drawings of centrally planned churches, some of which are represented using a plan view paired with a bird’s-eye view. The use of a bird’s-eye instead of an elevation represents an innovative depiction technique, which allows combining the immediacy of the perspective view with the measurability of the façades, and therefore to describe the three-dimensionality of the buildings. To understand the reasons behind the use of this original technique, the edifices’ shape and classify them, we decided to use 3D digital reconstruction techniques, for their ability to avoid misunderstandings in the reconstruction process and in the results. This article describes the method to create the digital models of sixteen churches. A Visual Programming Language (VPL) script was used as the 3D base for modelling the churches achieved from a classification code expressing the aggregative rules of the churches. Then, the geometric process for the construction of the plan and its relationship with the elevation measures were studied for each church. Finally, this information was used for the completion of the 3D models, distinguishing more output variants each time there was an inconsistency between plan and perspective view, a variability of one architectural element or an uncertainty.

El documento describe una metodología que cubre los procedimientos de levantamiento y las aplicaciones informáticas con el objetivo de convertir herramientas generalistas (teléfonos inteligentes) en dispositivos de adquisición rigurosa de BIC almacenados en los museos. Dos problemas diferentes se enfrentan: a) como las caracteristicas de dichos objetos a escala micro/meso afectan su documentación; b) desarrollo de una solución multipropósito para una adquisición de bajo costo y fácil de usar para digitalizar y visualizar artefactos BIC. Se presenta un procedimiento basado en un kit de adquisición digital destinado a lograr modelos y texturas confiables, así como representaciones de color precisas. Se han seleccionado varios objetos para probar la coherencia y flexibilidad de los métodos y técnicas propuestos, y los resultados se comparan con los de las técnicas de adquisición estándar.

Nowadays digital replicas of artefacts belonging to the Cultural Heritage (CH) are one of the most promising innovations for museums exhibitions, since they foster new forms of interaction with collections, at different scales. However, practical digitization is still a complex task dedicated to specialized operators. Due to these premises, this paper introduces a novel approach to support non-experts working in museums with robust, easy-to-use workflows based on low-cost widespread devices, aimed at the study, classification, preservation, communication and restoration of CH artefacts. The proposed methodology introduces an automated combination of acquisition, based on mobile equipment and visualization, based on Real-Time Rendering. After the description of devices used along the workflow, the paper focuses on image pre-processing and geometry processing techniques adopted to generate accurate 3D models from photographs. Assessment criteria for the developed process evaluation are illustrated. Tests of the methodology on some effective museum case studies are presented and discussed.

In questo lavoro presentiamo le caratteristiche di un innovativo sistema di documentazione, realizzato per il restauro della Fontana del Nettuno di Bologna, che usa un accurato modello tridimensionale per archiviare i dati raccolti in modo referenziato alla geometria 3D, per accedere agli stessi usando il modello 3D come indice spaziale ed infine realizzare mappature direttamente sulla superficie dell'opera.

The virtual reconstruction of no longer existing historic structures is obviously a subjective process that simplifies a visualization of the historical original monument. In this paper we define a methodological procedure focused on the validation of the 3D reconstructive model. The case study reported, cause of its complexity and overabundance of informations, allows to focus the attention to the level of subjectivity that concern the 3D modelling process trying to find a methodological solution to visualize the uncertainty level of the reconstruction process: the goal is to create an hypothetical virtual reconstruction based on a 3D model scientifically correct in morphological and dimensional terms derived from the integration of 3D recording, historical documentation and renaissance representations. A methodological workflow from data acquisition to the formulation of reliable hypotheses related to the 3D virtual-model of Porta Aurea ables to allow the verification of the assumptions used during the reconstruction pipeline is proposed.

Among the many cases concerning the process of digital hypothetical 3D reconstruction a particular case is constituted by never realized projects and plans. They constitute projects designed and remained on paper that, albeit documented by technical drawings, they pose the typical problems that are common to all other cases. From 3D reconstructions of transformed architectures, to destroyed/lost buildings and part of towns. This case studies start from original old drawings which has to be implemented by different kind of documentary sources, able to provide - by means evidence, induction, deduction, analogy - information characterized by different level of uncertainty and related to different level of accuracy. All methods adopted in a digital hypothetical 3D reconstruction process show us that the goal of all researchers is to be able to make explicit, or at least intelligible, through a graphical system a synthetic/communicative level representative or the value of the reconstructive process that is behind a particular result. The result of a reconstructive process acts in the definition of three areas intimately related one each other which concur to define the digital consistency of the artifact object of study: Shape (geometry, size, spatial position); Appearance (surface features); Constitutive elements (physical form, stratification of building/manufacturing systems) The paper, within a general framework aimed to use 3D models as a means to document and communicate the shape and appearance of never built architecture, as well as to depict temporal correspondence and allow the traceability of uncertainty and accuracy that characterizes each reconstructed element.

EnIn this paper we presented a BIM-based approach for the documentation of Architectural Heritage. Knowledge of classical architecture is first extracted from the treatises for parametric modeling in object level. Then we established a profile library based on semantic studies to sweep out different objects. Variants grow out from the parametric models by editing or regrouping parameters based on grammars. Multiple data including material, structure and real-life state are enriched with respect to different research motivations. The BIM models are expected to ease the modeling process and provide comprehensive data shared among different platforms for further simulations.ItIn questo articolo è presentata una procedura definita nell'ambito dei sistemi BIM con l'obiettivo di documentare il Patrimonio Architettonico. I dati conoscitivi relativi all'architettura classica sono, in una prima fase, ottenuti dai trattati al fine di modellare in maniera parametrica a livello di oggetti. Successivamente è stata definita una libreria di profili, basata su principi semantici, dalla quale è possibile ottenere oggetti differenti. Dati di natura differente, relativi ad esempio ai materiali, alle strutture, allo stato di fatto, sono implementati in funzione delle differenti esigenze. I modelli BIM hanno la potenzialità di facilitare le procedure di modellazione e di fornire informazioni e dati completi che possono essere condivisi tra piattaforme differenti per ulteriori simulazioni ed analisi.

ItLo sviluppo delle tecniche di modellazione ha scardinato lo schema concettuale che ha sempre considerato la figurazione come un semplice attributo e/o parte del sistema conoscitivo. Tali progressi permettono ora di focalizzare l'attenzione sull’impiego di modelli digitali 3D come matrice e nucleo aggregativo dei sistemi informativi, in grado di permette, da un lato, un facile accesso a strutture di dati estremamente complesse e, dall'altro, una costante guida dell’utente attraverso informazioni tipologicamente eterogenee.Questo articolo descrive un sistema informativo su web messo a punto con l'obiettivo di rendere disponibile su una piattaforma 3D GIS modelli tridimensionali di reperti archeologici ottenuti dal reale e con un dettaglio tipico della scala architettonica. All'interno dei siti di complessi archeologici vasti e complessi, i diversi tipi di artefatti devono essere modellati da differenti operatori, usando differenti metodologie e tecnologie ed elaborati in tempi e luoghi differenti; da tutto ciò scaturisce la necessità che i metodi per costruire i modelli 3D devono essere definiti a-priori, condivisi in maniera ampia e verificati a-posteriori.Il caso di studio riguarda il sito di Pompei, all'interno di un progetto di cooperazione con la Sovrintendenza di Pompei, finalizzato alla realizzazione di un archivio in grado di rendere disponibile la lunga storia di quell'area archeologica, la cui stratificazione storica porta indietro fino al 1738.I punti principali del progetto sono: (a) l'intero sistema informativo è accessibile via web e collegato ad GIS che permette la mappatura completa delle informazioni; (b) sono stati sviluppati differenti approcci conoscitivi e percettivi all'interno della matrice complessiva al fine di consentire l'accesso al patrimonio di informazioni che risale fino alla scoperta di Pompei; (c) sono stati definiti standard metodologici e tecnici con l'obiettivo di proporre linee guida comuni per la realizzazione di modelli 3D di un'area archeologica; (d) è stato reso possibile un impiego scientifico della modellazione tridimensionale quale strumento di supporto alle attività di scavo e per la conservazione dei dati per il progetto di un "sistema conoscitivo"; (e) i modelli digitali dei reperti archeologici sono collegati al loro insieme di informazioni eterogenee attraverso un sistema semantico di suddivisione e organizzazione degli elementi che li compongono e dei dati ad essi collegati.EnThe development of digital modeling techniques has undermined the conceptual scheme that has always regarded the representation as a simple attribute and/or part of the cognitive system. These advances allow us to focus on the use of 3D digital models as a matrix of aggregation, and core of information systems, able to allow an easy access to extremely complex data structures and a constant guide for the user through typologically heterogeneous information.This paper describes a web-based information system designed with the aim to make available on a 3D GIS platform reality-based 3D models representing archaeological finds at an architectural scale. In wide and complex archaeological sites, different artifacts need to be modeled by different operators, using different methodologies and technologies, working in different places and times, so that the methods to build them need to be defined a-priori, widely shared and verified a-posteriori.Our case study is the site of Pompeii, within a project of cooperation with the Soprintendenza of Pompeii, aimed at a restructured global archive of Pompeii to make the long history of the site accessible, crossed by the knowledge on the archaeological Vesuvian areas (since 1738) that has caused a stratified corpus of data.Main points of the project are: (a) the whole information system is WEB based and referred to an on line GIS for totally mapped information; (b) different perspectives of knowledge and perception have been developed within the global information system in order to also access the knowledge of the representations of Pompeii since its discovery; (c) definition of methodological and technical standards in order to propose common guidelines to design 3D models within an archaeological setting; (d) a scientific usage of 3D modeling to support excavation and conservation data designed as “systems of knowledge”; (e) the digital models of the finds are then linked to their related heterogeneous information using a semantic fragmentation and organization of elements and data.

Ensuring color fidelity in image-based 3D modeling of heritage scenarios is nowadays still an open research matter. Image colors are important during the data processing as they affect algorithm outcomes, therefore their correct treatment, reduction and enhancement is fundamental. In this contribution, we present an automated solution developed to improve the radiometric quality of an image datasets and the performances of two main steps of the photogrammetric pipeline (camera orientation and dense image matching). The suggested solution aims to achieve a robust automatic color balance and exposure equalization, stability of the RGB-to-gray image conversion and faithful color appearance of a digitized artifact. The innovative aspects of the article are: complete automation, better color target detection, a MATLAB implementation of the ACR scripts created by Fraser and the use of a specific weighted polynomial regression. A series of tests are presented to demonstrate the efficiency of the developed methodology and to evaluate color accuracy (‘color characterization’).