2.1. State of the art in the camerini reconstruction
The state of the art in the camerini 3D reconstruction will be described starting from four emblematic case studies.
a. Federico da Montefeltro's studiolo in the Palazzo Ducale of Urbino
One of the first cases of virtual reconstruction aimed at recovering the original forms of a studiolo is the camerino of Federico da Montefeltro, built in 1476 in the Ducal Palace of Urbino [7, 8]. It is one of the most illustrious examples of a Renaissance studiolo, celebrated for its wooden inlays and the wealth of artistic and scientific references embodied in its decorations. To celebrate this extraordinarily valuable space, an interdisciplinary project was launched in 2008, resulting in the exhibition Radici e sviluppo della tradizione scientifica urbinate: Federico da Montefeltro e il Gabinetto di Fisica dell’Università.
For this exhibition, the Gabinetto di Fisica of the Università degli Studi di Urbino Carlo Bo developed a 3D reconstruction that allows the visitor to explore the studiolo in an immersive and interactive experience, moving freely in space, zooming in and observing the details of the decorations, relocated according to their original arrangement. The aim was to reconstruct the original studiolo, reproducing even elements that no longer exist and making them available in an interactive mode.
The reconstruction process was carried out through extensive photographic mapping with chromatically calibrated images and planimetric surveys of the studiolo. This pioneering project also included an attempt to simulate the natural light entering the studiolo through the single window. However, the attention given to the simulation of the lighting components seems to be rather limited. The lighting was fixed, the materials were modeled in color only, and the optical reflection properties of the surfaces were not reproduced. This approach could not convincingly reproduce the complex interactions between light and matter that occur in the real environment. This prevented the full artistic value of the inlaid surfaces, where the play of light and shadow could have highlighted the subtlety of lines and meticulous detail. Another consequence of this design choice is that the pictorial decorations, rich in nuances and tonal subtleties, are less sharp and vivid. In fact, the static lighting reduces the perception of their three-dimensionality and volume, compromising the overall effect of depth and realism.
b. Federico da Montefeltro's second studiolo in Gubbio
Federico da Montefeltro's second
studiolo, located in the ducal palace in Gubbio and built between 1474 and 1482, has also been the subject of a virtual reconstruction, which has allowed its wider appreciation and historical understanding [
9]. The room, located on the main floor of the palace, was a small trapezoidal room with proportions like those of its counterpart in the Residence of Urbino: the longer sides measured 3.9 and 4.1 meters, the shorter ones 2.8 and 2 meters; the ceiling, with a coffered roof was placed at a height of about 4 meters. The room was famous for the inlaid wooden panels that lined it, characterized by striking three-dimensional visual illusions and decorated with images that symbolized Duke Frederick's erudition and interests. Above these wooden panels was placed a painted decorative apparatus, also like that of the Urbino
studiolo, consisting of portraits of 28 illustrious men of the time. This decorative apparatus was dismantled in 1939, and a few years later the wooden panels were purchased by the Metropolitan Museum in New York, where they are on display after a long restoration process.
The digital project launched in 2019 and curated by FrameLAB - a research laboratory of the Department of Cultural Heritage of the University of Bologna - in collaboration with the Polo Museale dell'Umbria, the Polytechnic of Turin and the University of Perugia aims to restore the original appearance of the studiolo in its historical location and, at the same time, to remedy, albeit partially, the current dispersion of its furnishings.
The result is a metrically accurate and fully navigable digital replica of the studiolo, conceived as a technological support to the on-site physical replica set up in 2009. In the physical room, in fact, there is a 32” touch-screen station allowing visitors to explore in detail and at 360° the high-resolution video-narrative of the studiolo. The model used by the application is the result of a digitization process articulated in several phases: a first phase of high-resolution photographic acquisition of the original inlays, carried out directly at the Metropolitan Museum, which produced chromatically correct images; a second phase, carried out by the Department of Architecture and Design of the Polytechnic of Turin, which generated 3D surveys of the Camerino space using laser scanning technology. This digital reconstruction, enriched with visual and sound elements, allows the exploration of the studiolo according to gamification logic, allowing the user to move in the virtual space with first person view and to observe every detail from different angles.
Despite the wealth of information, the lighting reproduction is static and not very faithful to the original conditions of the studiolo, which was probably designed to be experienced in an intimate atmosphere, fostered by a semi-darkness conducive to reflection and contemplation. The inlays were digitally assembled by reproducing the lighting effects closely related to the illusionistic chiaroscuro of the reliefs, carefully preserved even in the post-production phase. However, the choice of natural and diffuse lighting, generally from above, seems questionable given the absence of a window at the top of the three-dimensional space.
c. Belfiore's studiolo in Ferrara
The Studiolo di Belfiore was one of the most important rooms of the vanished Delizia di Belfiore, one of the urban and suburban residences of the Este family in the Duchy of Ferrara. Built at the end of the 14th century, the Delizia was almost destroyed by fire, but in the 15th century it was one of the most admired residences of the time.
The studiolo was about 54 square meters, much larger than other examples of studioli that still exist today (those of Federico da Montefeltro were about 18 square meters in the case of Urbino and 15 square meters in the case of Gubbio; the 16th-century studiolo of Alfonso I d'Este measured about 24 square meters) and was lit by two large windows (1.60 m x 0.90 m). Above these were the famous paintings of the Muses, framed by wooden elements that simulated architectural frames. Despite the devastation suffered by the Delizia over the centuries, including fires and military attacks, the paintings have been preserved and are now distributed among several museums in Europe.
The Belfiore
studiolo was the subject of a valorization project launched in 2019 by the collaboration between FrameLAB of the University of Bologna, the Pinacoteca Nazionale di Ferrara and the Gallerie Estensi, focusing on digital storytelling and privileging the illustration of the iconographic program and the history of the
studiolo over a navigable three-dimensional reconstruction [
10]. This choice was motivated by the lack of detailed sources on the form of the wooden inlays and the composition and placement of the original furnishings, a circumstance that could have compromised the philological accuracy of the result. The three-dimensional model of the
studiolo that appears in the video is based on data from the Autentico dei Lavoratori, a historical document that recorded the fees and activities of the craftsmen involved in the creation of the
studiolo. In the model, the shape of the inlays, which is not explicitly described in the sources, was reconstructed by copying that of other panels made by the same craftsman: Arduino da Baiso.
The wooden essences replicated in the 3D models were photorealistically reproduced, even adding minor imperfections caused by time. The six canvases of the Muses, placed on the wall opposite the entrance, were digitized in high resolution using photogrammetry and then colorimetrically corrected to equalize their light and color balance, making the visual perception of the works homogeneous in the digital model. Despite the presence of two large ultramarine glass windows, no attempt was made to replicate the effect of natural light in the room. The lack of detailed documentation on the actual lighting configuration makes a philologically accurate reconstruction impossible. It is not possible to reliably reproduce the color and transparency of the glass panes, nor the direction and intensity of the natural light passing through them.
d. The studiolo of Isabella d'Este in Mantua
After her marriage to Francesco II Gonzaga in 1490, Isabella d'Este settled in the apartments on the main floor of the ducal castle of San Giorgio in Mantua. Here she had a small, dimly lit room without a fireplace built, where she enjoyed her pastimes, studies, and correspondence. The room housed a priceless collection of books, works of art, archaeological finds, and naturalistic curiosities-an impressive collection that was the pride of the Gonzaga family until it was dispersed in the seventeenth century. As lover of music and arts, Isabella developed a decorative program for her studiolo based on mythological and allegorical themes drawn from ancient literature to celebrate her family. The studiolo was therefore the home of several precious paintings, according to a project that aimed to “compete” different artists of the time by having them work on canvases of the same size, all with mythological themes. The works in the studiolo, now in the Louvre Museum, had illustrious authors, including Pietro Perugino, Andrea Mantegna, Lorenzo Costa and Correggio. When her husband Francesco Gonzaga died in 1519, Isabella moved to the widow's apartment in another wing of the Mantua castle. Because of this move, the camerino/studiolo and the adjoining room, known as La Grotta, were dismantled and reassembled in new rooms located in the Marquise's second apartment.
After Isabella's death, the studiolo was abandoned and the paintings were sold. Today, therefore, the studiolo and the grotta are still structurally intact, but the heritage they contain has been dispersed, and the original appearance of these rooms has been lost.
The IDEA (Isabella d'Este Archive) project, an academic initiative designed to study the Italian Renaissance through the figure of Isabella, has breathed new life into these two precious rooms. It is a research project that takes an interdisciplinary approach, combining 3D modeling technologies with textual analysis and philological research to virtually reconstruct every aspect of Isabella's life and collections [
11]. The result is a complex digital platform, hosted online and fully accessible, that brings together information and documents about the Marquise's correspondence and legacy, digitally reconstructed through virtual and augmented reality. All reconstructions will be accompanied by accurate analysis based on historical documents, such as inventories and correspondence, to accurately represent the cultural and artistic environment of the time. The project therefore aims not only to preserve and make accessible the materials, but also to stimulate new research and provide immersive experiences that connect modern audiences with the historical past.
The reconstruction of the studiolo and Isabella's grotta is the result of a process combining several digital modeling and visualization techniques, ensuring a high level of historical fidelity and realism. Acquisition of the existing was accomplished by photogrammetry, a technique that allowed for precise measurements of the physical space. The resulting web application can be accessed via browser and allows visitors to explore the studiolo and the grotta through three different modes of navigation: first-person, third-person, in which the camera orbits an avatar representing Isabella d'Este, and close-up, allowing them to get closer to the objects to observe their details and access a catalog of in-depth information about the works present, such as dimensions, inventories, and bibliographical references.
Despite the accuracy and level of detail achieved by this reconstruction, there emerges a lack of clear architectural semantics that prevents the association of 2D analysis with semantically geolocated 3D and the simulation of night light, which probably represented the most frequently experienced lighting condition in the studiolo. The integration of such elements would further enrich the immersive experience, offering a more complete understanding of the original atmosphere of the place.
Summing up, all the projects described were carried out according to a multidisciplinary approach that integrated scientific documentation methods and technological tools, demonstrating how the mixture of modeling techniques and digital visualization can restore new life to lost spaces. However, for better compliance with historical truth, aspects such as semantic modeling, explicit stating of reconstructive sources and their reliability for each part, methods of surveying, replication of optical reflection properties of materials, and the study of the effect of light must be carefully considered.
2.2. State of the Art in the Architecture Historical Reconstruction
In the last years an extensive literature was produced concerning the topic of the virtual reconstruction of historical buildings that can be easily and without any lack of information adapted to the interiors space and then also to the camerini [12, 13, 14, 15, 16].
This section reviews and analyzes these and related studies focusing on two main different topics concerning 3D model quality criteria:
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historical reconstruction source reliability
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geometric and photometric.
In the last decade, reconstructive hypotheses of buildings in a state of ruin or significantly altered by time and events since their construction, unbuilt of disappeared have been the subject of extensive literature [
17]. The aim is to broadly distinguish between the function of the 3D model of a purely illustrative type and a 3D model for scientific purposes, i.e., a medium capable of properly understanding an ancient building (existing or not), its function, use, etc. and specifically to systematize and ensure the transparency of the information collected and processed to create digital models that are accurate and adhere to the original with varying degrees of reliability [
18].
Over the years, various authors have proposed different solutions for conceptualizing and visualizing reconstructive hypotheses, introducing numerous concepts essential for accurate 3D reconstruction. Among these, the level of reliability (LOR) [
19] assigned to every piece of evidence is crucial, as it determines the confidence in the data used for reconstruction. This concept ensures that each piece of evidence is evaluated for its authenticity and relevance, providing a foundation for the reconstruction process. Another significant concept is temporal uncertainty across multiple sets of data with diverse dating [
20]. This addresses the challenges of integrating data from different time periods and sources, acknowledging the inherent uncertainties in dating and temporal alignment. By considering temporal uncertainty, reconstructions can more accurately reflect the historical context and changes over time.
Other authors have introduced additional terms to further refine the conceptual framework for 3D reconstructions [
21]. E.g., the level of existence (LOE) is a concept that categorizes the degree to which different elements of a reconstruction are supported by evidence. This helps in distinguishing between well-documented features and those that are more speculative, ensuring transparency in the reconstruction process. Similarly, the Level of Geometrical Reliability (LOGR) assesses the accuracy of the geometric representation of reconstructed elements. This metric is vital for ensuring that the spatial dimensions and relationships within the reconstruction are as precise as possible, based on the available evidence. The Index of Reliability (IR) is another important concept, providing a quantitative measure of the overall reliability of the reconstruction. This index combines various factors, including the quality of evidence, temporal uncertainty, and geometrical accuracy, to give a comprehensive assessment of the reconstruction’s credibility.
These concepts are complemented by the development of a graphical code capable of visually conveying the certainty of reconstructive elements through Probability Maps and Historical/Archaeological Evidence scale [
22]. Several scholars have theorized about the use of a semantic structure in digital modelling as a potential way to facilitate the reading and understanding of the reconstructive hypothesis.
The Extended Matrix (EM), developed by CNR-ISPC in Rome [
23], is a formal language designed to trace virtual reconstruction processes. This tool is used by archaeologists and cultural heritage specialists to robustly document their scientific activities. EM employs a node-based language and represents certainty by means of standardized colors: a sort of evidence scale based on the binary concept of existing or absence of documentary units. Color code has the following meaning:
Red: I am sure it exists because it is preserved;
Orange: I am sure it existed because there is documentation about it;
Blue: I am sure something existed, but I only know partial properties;
Yellow: I am sure it existed, but I am not sure about its original position;
Dark yellow: I am sure something existed, but I am not sure about its original position;
Green: I believe it existed. My reconstruction is not based on in situ elements (all those parts for which we have no structural or archaeological evidence, but their reconstruction is entrusted to comparisons or interpreted sources).
Aparicio and Figueiredo [
24] propose a system for organizing the virtual reconstruction of ancient buildings based on Reconstructive Units (RU) and a scale of historical-archaeological evidence. The RU refers to discrete components of a building that can be reconstructed individually based on available evidence, namely a sort of reconstruction semantics. The scale of historical-archaeological evidence evaluates the degree of certainty of each reconstruction, ranging from speculative to highly reliable. This framework allows for a more systematic and transparent approach to virtual reconstructions, ensuring that they are based on varying levels of archaeological data and historical understanding.
This method has been successfully employed in high-value archaeological research [
25], demonstrating its effectiveness in ensuring accurate and well-documented reconstructions. However, it can also be applied as a general criterion for interpretation and organization of work in other fields, such as the study of Renaissance
camerini. By adapting the principles of RU and the evidence scale, this approach can provide concepts and tools for a robust framework for 3D reconstruction, ensuring that hypothesis acknowledged are not only visually accurate but also scientifically credible and transparent. As a matter of fact, RU are easily implementable even in interiors for exhibition purposes. In the broader context of semantics, they produce a hierarchy of models, making validation more straightforward and elementary. We improved these methods by customizing them for the case of
camerini and incorporating perceptual criteria motivated by the use of these spaces, i.e., rooms designed for observing artworks in their true aesthetic context. However, it appears that an important perceptual dimension is lacking in this line of research, which is primarily based on the RU and the scale of historical-archaeological evidence. Specifically, the reliability of a 3D reconstruction of an ancient building is not a general criterion but rather depends on the proximity of the observer to the individual RU. This aspect has been developed as an original contribution to the broader discourse on the credibility of 3D reconstructions in archaeological studies.
- b.
Geometric and Radiometric 3D Model Quality Criteria
From the bibliographic review, e.g. in [
17], several implementable solutions emerge as applicable to the workflow involved in the reconstruction of Renaissance
camerini.
For currently standing buildings with historic interiors that no longer exist, it is recommended to begin with reliable 3D surveys to create digital models that accurately reflect reality[
12]. This method helps to address the persistent issue of relying on less reliable solutions based on outdated and unverified two-dimensional drawings.
The second aspect is the transparency and integration of the information that led to the realization of a specific reconstructive solution. To effectively integrate information derived from literary sources, historical images, or plans and elevations representing the state of a room at a specific moment, the most effective solution is a semantic subdivision of the 3D model. In this approach, each granular element is associated with a specific reliability assessment.
A key aspect of the process involved in generating individual RU is their origin. In this context, the reconstructions are primarily grounded in reality-based data, ensuring a robust and accurate foundation for further modelling development.
If a building is well preserved, it is possible to digitize parts of it that are compatible with a space that no longer exists. Active and passive sensors can also be used to document its shape, color, and other properties useful for virtual reconstruction. When specific information is not available, it is necessary to use direct modeling and texturing techniques. In such cases, generic textures are used to represent the appearance of the building. However, the practice of using such 2D assets from collections or repositories without any spatialization of the contents is not advisable, as they produce effects that are difficult to verify through standardized evaluation processes [
26]. However, it is important to note that the use of such techniques, particularly for elements or the entire “envelope” of the room, significantly reduces the quality of the reconstruction.
In the contemporary panorama of 3D modeling for enhanced interaction, various approaches can be utilized for the reconstruction of historical interiors and works of art. These techniques leverage data obtained through laser scanning and photogrammetry, each supported by a growing body of research [27, 28, 29, 30].
In general, a crucial role is played by the approach to scene optimization and several possibilities can be put into practice: using smart decimation by means of triangles, isotropic quadrilateral meshes (quad-remeshing), or through manual polygonal modelling operations, or retopology) [31, 32].
These techniques are recommended at the final stage of geometric reconstruction from reality-based data. This step, though not always mentioned in scientific literature, allows for better management of geometries and the optical reflectance of materials inferred in the geometric model. Optimized parametrization provides high control in geometric and mapping models, especially for textures that contribute to the realistic simulation of less common materials, as opposed to the widely used Lambertian approximations in architecture. Additionally, this technique can be used when reconstructing interior spaces from scratch.
A second main topic concerns the reproduction of the physical reflection properties of the materials that make up the surfaces of the interior space (floor, ceiling, walls, transparent surfaces, such as windows and decorations).
In this sense, the scientific literature appears much less abundant and generally more focused on the integration of different models within original environments without emphasizing the complete light-material interaction enabled by contemporary CGI [33, 34].
However, when working within the fields of art and architectural history, the chromatic, material, and lighting aspects of artworks and environments are, and should be, essential for the proper use of 3D reconstructions for scientific purposes.
There are indeed examples of 3D reconstructions that pay careful attention to reconstruction of materials and textures of surfaces of the room [35, 36], but they are quantitatively fewer than the number of studies on 3D reconstructions at the architectural scale (general external views, perspectives, and axonometric cutaways) and urban scale. In other words, reconstructions that integrate both architectural interiors and the “microscale” perception of artworks highlight a significant gap in the current scientific literature.
Based on the studies analyzed, it is evident that there is a need to develop a working method that achieves complete realism in 3D reconstruction solutions for interiors and exhibited artworks. This method should advance the integration of philological studies, ensure meticulous data capture and management of architectures and artworks, and, importantly, fully exploit the visualization capabilities afforded by the current state-of-the-art physically accurate visualization technologies.