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Virtual content needs virtual environment to be fully experienced. This page is a companion material to the paper

Angheluță, L., Țentea, O. Dozsa, AL. Virtual reconstruction and restoration of an uncommon bronze vessel from the Mălăiești Roman fort, Cercetări Arheologice 29.1, 2022

and is intended to be an immersive virtual archaeology experience for a single artefact, the Mălăiești bronze vessel.

Mălăiești bronze vessel decoration detail in BW

Decoration detail of the bronze vessel from Mălăiești Roman Fort

The most accessible medium for this approach is a tool in form of a public online web page which can present text, images and interactive 3D content. The purpose of this tool is to offer an alternate way for narrative in virtual archaeology. In this case the presentation contains: artefact general presentation, a summary of previous scientific studies and investigations, the 3D digitization process, and results with full paradata, scientific 3D viewer with features like measuring, raking light inspection, profile extraction, virtual restoration and anastylosis 3D viewer, virtual reconstruction proposal 3D viewer.

Archaeological context

The fort from Mălăiești is part of a small group of fortifications built by the Roman army north of Danube, during their conquest campaigns in Dacia. This fort was built during the advances of the Roman armies across the Carpathian Mountains to the present Transylvania region, starting with 101 A.D. and was functional until 118 A.D., the first year of the reign of emperor Hadrian, Trajan’s successor. The short-term functioning of this fort allows for a detailed reconstruction of a well-defined historical sequence, making this site a reference standard for the constructions and artefacts chronologically framed in the first years of the second century A.D.

The fort

The area of the fort was severely affected by agricultural leveling back in the 1980's, which made difficult the identification of the routes of the wooden walls and the distribution of the barracks buildings. The archaeological research (2011-2019) identified the burning level of the barracks, corresponding to the time when the garrison left. Based on this research it was concluded that the camp had 24 barracks, which means a considerable number of soldiers were hosted, possibly a full garrison for a cohors militaria or ala quingenaria, a unit between 600 and 800 soldiers. The name of this troop remains unknown. The correlation of the data gathered from geophysical measurements, regarding the camp plan, with those from the extensive excavations (~450 m2) around a military barracks from the sinister praetentura revealed important information about the architecture and the internal structure of the building where the vessel was found.

The excavated barrack had 8 bedrooms (contubernia), with a usable area of about 12 m2, doubled to the south by a corridor. The officer’s residence (~ 80 m2, divided into several rooms) was located at the eastern end of the barrack. A cellar was identified under the south-east room, located in the corner of the apartment. The vessel was found in the cellar of this barrack along with several of its fragments and other objects with a significant number amphorae used for wine, olive oil and garrum, indicating their storage on wooden shelves and supports.

Mălăiești fort location on map

Location of the Mălăiești Roman Fort

The artefact

The object was found partially damaged with a side wall bashed in and the base detached. It had some missing parts, of which several fragments were found nearby. The surface was covered with green, brown and black encrustation, due to corrosion processes.

Mălăiești bronze vessel photos on site and in lab

The bronze vessel: photo documentation

The vessel has a globular body, with rounded shoulder, wide neck, and slightly inverted rim. It had flat base (now detached), made from a different metal sheet. From the point of view of the production process, the vessel was initially cast as a rough cylinder, which was subsequently hammered, in order to obtain the final shape. The body preserves a dotted decoration (possibly made by embossing), organized in two registers (as emphasized after 3D digitization: one towards the base, the other under the rim) divided by an undecorated strip on the shoulder. The remaining part of its neck presents only one metal loop, a band of the same material as the vessel, with a width 6.3 mm and 1 mm thickness, bended and rounded, with 8mm diameter, which suggests it had a handle of unknown design at some point, but now lost.

  • Height: 15.6 cm
  • Neck diameter: 12 cm
  • Maximum body diameter: 18.7 cm
  • Base diameter: 13.5 cm
  • Wall thickness: 1.77 mm - 2.33 mm
  • Total weight: 374 g

Multi-analytical studies

These studies are part of another separate work published as "Angheluță, L., Țentea, O., Ghervase, L., Cortea, I., Dinu, M., Ratoiu, L., Pârău, A. 2022. Integrated multi-analytical study of the bronze vessel from Mălăiești Roman fort. Journal of Ancient History and Archaeology 9 (1)". The opportunity of documenting the vessel, through a multi-analytical integrated approach right after its discovery was a great advantage for its characterization, especially for studying the corrosion and overall conservation state.

In this study, in support of the archaeological research, two main aspects were considered: an accurate 3D digitization followed by a virtual reconstruction of the vessel, and a thorough physico-chemical and imaging characterization of its conservation state. The conservation state was assessed using: imaging techniques (X-ray digital radiographs and hyperspectral image processing) and spectroscopy investigations: Fourier Transform infrared (FTIR) spectroscopy, X-ray fluorescence (XRF), laser-induced breakdown spectroscopy (LIBS) and X-ray diffraction (XRD).

Radiographs

The X-ray imaging was carried out in two sessions: one right after the unearthing, while still in a box filled with earth and another one after the preliminary cleaning. The first exposure ruled out the possibility of other objects being hidden in the soil inside the vessel, useful for the first mechanical cleaning of the vessel. The second exposure, after the cleaning, was helpful in identifying traces specific for the manufacturing process (such as the hammering process for the base), along with the assessment of the vessel's state of degradation - wall thickness, integrity and heterogeneity.

Photo explanation: Left: side view from second session; Right top view from first session.

 

Mălăiești bronze vessel x-ray plates selection

X-ray imaging plates

XRD and FTIR

Multiple degradation products of the main elements have been detected through XRD: brochantite, malachite, cerussite, cuprite, atacamite, cassiterite, covellite, tenorite, pyromorphite and libethenite. Each of them is related either to the raw material or to the conditions of the burial environment. For instance, the presence of phosphates correlated with the lack of any organic material leads to the idea that the soil had been used for agricultural practices. The soil has a low-sulfur content, which is indicated by the presence of brochantite, consistent with soil leaching, either from groundwater sources (which also correlates with the presence of copper oxide) or from watering of the crops. Together, these findings create the image of the artefact being buried in a cultivated, fertilized and frequently watered soil.

XRF and LIBS

XRF analysis of the bulk metal, based on empirical calibrations for copper, identified a Cu-Sn alloy, with approximately 97 wt% for Cu and 1.18 wt% for Sn.

The stratigraphical analysis performed with LIBS revealed higher Cu levels towards the bulk material, as compared to the surface of the samples. As no organic traces had been identified neither through FTIR nor GC-MS, there were no viable hypothesis regarding the use of the vessel. This aspect was revealed by the identification of a tin coating on the inside of the vessel (higher Sn and Pb concentration in the first spectra recorded for the silvery areas on the interior of the base), which drastically reduced the possibilities, suggesting that it couldn’t have been used for cooking, nor in contact with direct fire or extreme heat, and was probably used just for storing food or liquids.

Mălăiești bronze vessel spectroscopy data

Selection of spectroscopy data

3D digitization

This process is an important step in the early stages of the artifact life as it can serve as an instance of its early conservation state, could be used to help against illicit trafficking practices or improper cultural goods management (damage during transport, storage, etc.), but it also has an important value for both scientific and public dissemination deliverables. It must be stated that this type of documentation cannot replace the historical value of any artefact, monument, or other real element it represents. It does not save nor preserve the object any other way than as digital information that can easily serve for further studies.

In this case, the aim of 3D digitization was on one hand to document the object’s surface before the final physical restoration stage by scanning the main body and its biggest fragments for both geometrical and chromatic properties, and on the other hand to use the digitized 3D model further in the virtual reconstruction processes and finally to have it published in an online virtual medium for general public and scientific expertise access.

Method

After assessing the goals of this 3D digitization and the resources available it was decided that the best method to use, in this case, was photogrammetry. Data acquisition was done using an automated rotating table synchronized with the photo camera through wireless infrared technology. The rotating parameters (speed and number of steps) were setup through a mobile app that controlled the whole syncing process. Lighting was ensured with LED lights in a special photography tent with a white background. The accuracy of the colors and color temperature was corrected using color and white balance witness cards.

Two meshes were exported: the decimated one and the original raw result, both in OBJ format. The simplified model was first used for profile extraction and other precise measurements like volume, areas, decoration spots diameters or wall thicknesses along the profile, while the raw result (also much bigger in terms of disk storage) was used for retopology.

Paradata

Attribute Properties
Polygons 2.000.000
Textures 3
Method Photogrammetry
Date 10.10.2021
3D Author Laurențiu Angheluță
Software used Agisoft Metashape PRO 1.8
Images 395
Image resolution 42 mpx
Sensor ILCE ARIII
Lens focal 35 mm
Light source White flourescent
Raw scan polygons 45.000.000
Mălăiești bronze vessel 3D digitization

3D Digitization results - still renders. Left: Textured model; Right: Matcap detail enhanced render

Virtual exploration

The 3D viewers used, although different in concept, are all based on the same technology: WebGL. The first one, the viewer with scientific features, is an open-source resource developed by the Visual Computing Lab of ISTI-CNR and requires a few adjustments before use, like converting the 3D model into a proprietary format. The other viewers are simpler and were developed for this study, using ThreeJS and are designed only for simple inspection of the 3D models.

Scientific viewer: the digitized model

This viewer allows an advanced inspection of the 3D digitized model of the bronze vessel. You can measure surface features, export slices on all three axis as jpegs or use a moving light for surface feature highlighting.

Virtual reconstruction model

Comparing the shapes of the similar objects found it was concluded that the shape of the vessel was globular and that the missing parts did not contain elements with a different shape profile from the rest of the body that is not damaged. In this regard, the profile of the undamaged area of the vessel was used as the shape for the full vessel virtual reconstruction hypothesis. The thickness of the walls was also extracted from the 3D digitized model (1.77 mm for the upper neck area and 2.37 mm for the area in the vessel’s the largest diameter). For the virtual reconstruction, considering the small difference between these values (0.5 mm) it was decided for an average value of 2 mm for the whole vessel wall thickness.

Mălăiești bronze vessel virtual reconstruction

Stages of the virtual reconstruction: a-hard surface modeling (wireframe view); b- normal map texture for the decoration; c- UV mapping of areas with different properties of the object (interior, exterior, decoration, polished median band); c-f - rendered views of the final reconstruction

Virtual restoration/anastylosis model

The virtual approach is extremely useful as it does not require the manipulation of the physical objects. The digitized fragments were virtually positioned, using the same software program, considering the clues for their original position. These clues usually come from closely investigating any possible connection points, process much eased by inspecting the 3D digitized model, and studying the shape, curvature of the surface and the decoration (if any). The latter clues help to approximate the register the fragments are most likely to have been part of, in lack of any information regarding their connection areas to the main body. Heavy corrosion usually deforms these connection points making this process really complicated.

Mălăiești bronze vessel virtual anastylosis

Left: virtual anastylosis of the vessel main body and the base fragment; right: hypothetic original shape as a translucid virtual prosthetic

References

  • Angheluță, L., Țentea, O. and Dozsa, AL. Virtual reconstruction and restoration of an uncommon bronze vessel from the Mălăiești Roman fort, Cercetări Arheologice 29.1, 2022
  • Angheluță, L., Țentea, O., Ghervase, L., Cortea, I., Dinu, M., Ratoiu, L., Pârău, A., Integrated multi-analytical study of the bronze vessel from Mălăiești Roman fort, Journal of Ancient History and Archaeology 9 (1), 2022
  • Mustață, S. and Țentea, O., The Roman metal vessels from Mălăiești Roman fort, In: V. Bârcă, S. Mustață, V.-A. Lăzărescu, V. Rusu-Bolindeț, D. Matei (eds.), Faber, Studies in Honour of Sorin Cociș ay his 65th Anniversary, Cluj-Napoca 2022
  • Țentea, O. and Călina, V., Peisajul arheologic al castrului Mălăiești, Cercetări Arheologice 28, 2019, 169-196. DOI: https://doi.org/10.46535/ca.26.06
  • Țentea, O., Popa, Al. and Cîmpeanu, A. Mălăiești., A trajanic fort in Muntenia – the results of recent magnetometric surveys, Acta Musei Napocensis 55, I, 2018, 227–240