Hello everyone.
As you may know, we at Arc-Team are particularly connected to the ArcheoFOSS workshop, a meeting on archaeology and open-source software that we helped found in 2006. Last December, the seventeenth edition took place in Turin (Piedmont, Italy) and, after a couple of years of absence, we were able to participate again. Our presentation was titled "Digital twins of archaeological finds. Open source technologies applied to 3D scanning. Methodologies, limits, and results" and dealt, among other things, with a topic that is very dear to me: how to carry out good 3D archaeological documentations (with open-source software) of artifacts with "difficult" surfaces, such as gold or fur.
Today, I took the time to upload our presentation, of which you can see the initial slide below. You can find our presentation at this address.
Below is a brief summary of the topics covered slide by slide:
SLIDE 1
Simply the title.
SLIDE 2
The institutions involved in the presented projects: MArTA (Museo Archeologico Nazionale di Taranto), Südtiroler Archäologiemuseum - Museo Archeologico dell'Alto Adige, UMST (Unità di Missione Strategica della Provincia Autonoma di Trento), and, of course, Arc-Team.
SLIDE 3
MArTA, perhaps the most important museum in Magna Graecia, famous for its collection of gold items.
SLIDE 4
Südtiroler Archäologiemuseum - Museo Archeologico dell'Alto Adige, famous for hosting the mummy of Ötzi (the Similaun Man).
SLIDE 5
The Autonomous Province of Trento, which, with its offices, is responsible for the conservation and enhancement of Cultural Heritage in Trentino (Italy).
SLIDE 6
Arc-Team: a company specialized in various archaeological sectors, including FFR (Forensic Facial Reconstruction), Field Archaeology, Digital Archaeology, Mission Abroad, Archaeorobotics, Extreme Archaeology, etc...
SLIDE 7
An example of the wide range of artifacts stored at MArTA.
SLIDE 8
An example of the type of artifacts associated with the Similaun Man's mummy (mostly made of natural materials such as wood, leather, fur, etc.).
SLIDE 9
An example of the various types of archaeological projects carried out by Arc-Team in the Autonomous Province of Trentino - Alto Adige/Südtirol.
SLIDE 10
A gallery concerning issues related to 3D documentation of artifacts in the mentioned contexts. Main issues include the size (from very large to very small) of artifacts; logistics (with non-dismountable exhibits, non-detachable display cases, old museum contexts, crowded visitor rooms, etc.); the complexity of some objects (which may require documenting both the internal and external surfaces in 3D, even in the case of very small artifacts); the variability of the characteristics of different surfaces (including extremely reflective ones, such as gold, silver, and sometimes bronze; semi-transparent ones, such as glass; those that absorb light, such as skin and certain types of wood; and very particular ones, such as fur).
SLIDE 11
The solution that Arc-Team prefers for 3D archaeological documentation: SfM (Structure from Motion). In the photo, Alessandro Bezzi, Luca Bezzi, and Kalus Kerkow in front of the TOPOI Excellence Cluster lion in Berlin (Germany), documented in 3D in 2009 with the open-source PPT (Python Photogrammetry Toolbox) software developed by the Frenchman Pierre Moulon.
SLIDE 12
The workflow PPT (now obsolete), which relied on the open-source Bundler and PMVS software.
SLIDE 13
The level of detail/accuracy achieved with PPT in 2009.
SLIDE 14
The current situation in the panorama of open-source SfM software. Among the various options: OpenDroneMap (excellent for archaeological excavation and aerial documentation), openMVG, Regard3D, MicMac (excellent for aerial documentation), orthoBlender (excellent for FFR and any project involving a 3D modeling step), Colmap, openMVS, MeshRoom (excellent in creating and managing raster textures).
SLIDE 15
A slide to show the versatility of a 3D approach based on SfM, capable of operating in extreme contexts (Underwater Archaeology, Aerial Archaeology, Glacial Archaeology, High Mountain Archaeology, Speleoarchaeology), as well as in logistically simpler contexts (Field Archaeology, museums), based on very simple equipment such as a camera, easily usable even during missions abroad.
SLIDE 16
A video of the 3D documentation of a speleoarchaeological context: the Grotta del Teschio, investigated by Arc-Team at the end of 2023 on Monte Stivo (southern Trentino, Italy).
SLIDE 17
Issues of 3D documentation of artifacts related to light: problems due to ambient light and problems due to reflected light.
SLIDE 18
A typical example of 3D documentation problems related to ambient light: underwater documentation (solvable with pre-processing photos through the open-source software ImageMagick). Specifically, the photo shows the example of the Barca dei Diavoli (which I have already talked about in various posts here on ATOR in the past).
SLIDE 19
The 3D reconstruction and vector drawing (from GIS) of the Barca dei Diavoli.
SLIDE 20
Another example of problems arising from ambient light, this time inside a museum (MArta): presence of poorly lit areas; artificial light spots; ambient light (sun) divided into three different entry points from the windows of the wall; presence of large reflective surfaces.
SLIDE 21
Solutions to eliminate or mitigate problems due to ambient light inside museums: dark or reflective panels, special flashes (ring-type), etc.
SLIDE 22
A video showing the example of 3D documentation of a marble head not removable from its museum location. Documentation is carried out through SfM with the help of a ring flash and two LED panels for uniform lighting.
SLIDE 23
Another example of correcting ambient light in a museum (in cases where small objects removable from display locations are documented), through the use of simple photographic boxes.
SLIDE 24
Problems with reflected light and the dynamics of light on reflective surfaces. The first image shows Blender's mascot (Suzanne) in gold, as it would appear in reality, with both diffuse and specular reflection light. The two derived images show, on the left, Suzanne with only diffuse light, and on the right, Suzanne with only specular reflection light. This slide serves to show the technique normally used to document objects with a very reflective surface through SfM: an attempt is made to obtain only photographs with diffuse light (without specular reflection light), from which 3D is then extracted.
SLIDE 25
In some cases, such as bronze, to obtain reflection-free photos, it is sufficient to use a polarizing filter on the camera (and rotate it according to the direction of the reflection). In the example shown in the photo, a bronze helmet kept at MArTA.
SLIDE 26
The 3D result of the helmet from the previous slide.
SLIDE 27
Another example of a complex 3D from MArTA: a semitransparent glass cinerary urn with the amphora in which was housed.
SLIDE 28
An example of 3D with reflected light from organic materials (wood, leather strings): Ötzi's axe.
SLIDE 29
The technique used by Arc-Team at MArTA for the most complex objects due to the high level of light reflection: gold items. The image reproduces the arrangement of a darkroom in the server room, with the polarization (via a film) of the only light source and the use of a second polarizing filter on the camera.
SLIDE 30
An image illustrating the removal of reflection from a gold crown.
SLIDE 31
A video showing the 3D model obtained from one of MArTA's most complex gold crowns (due to the complexity of the decoration).
SLIDE 32
The concept of Archaeological Tolerance to be applied to the level of precision and accuracy intended to be achieved in 3D surveys (both of artifacts and excavation contexts).
SLIDE 33
An example of a special case: the 3D documentation (for FFR) of the face of the mummy of S. Caterina Fieschi Adorno (from Genoa).
SLIDE 34
The difficulty was due to the fact that the crystal coffin in which the saint's body is preserved could not be opened. For this reason, Arc-Team documented the face by placing the camera directly on the glass slabs of the coffin. Obviously, with such forced shooting points and the low quality of the photos, due to the glass panels, a 3D was obtained that was not sufficient for the continuation of the work (the identification of restoration interventions, on the nose and mouth) carried out in the 1960s. Nevertheless, it was possible to increase the level of detail of the 3D documentation, thanks to Cicero Moraes (FFR expert at Arc-Team), who used a new technique in Blender (through the Map Displacement modifier), later integrated into orthoBlender.
SLIDE 35
This technique is very useful for increasing the detail of the docuemntations of particular surfaces such as fabrics or skin. The example reported here concerns a detail of Ötzi's leggings.
SLIDE 36
Another example of the Map Displacement Modifier, this time applied to Ötzi's bear fur hat. However, as seen, this modifier is unable to increase the detail of the docuemntation in areas where the fur has been preserved.
SLIDE 37
At the moment, the best method for rendering fur (at least in 3D videos) is the use of the new technique NERF (Neural Radiance Field), through AI and open-source software like NERFstudio.
SLIDE 38
The result of the 3D of Ötzi's hat in NERFstudio.
SLIDE 39
Of course, Archaeological Tolerance in 3D surveys of artifacts must also be calibrated based on the very purpose of digital twins. For example, Ötzi's artifacts were 3D documented for conservative purposes, while the skull of the Grotta del Teschio was documented as part of normal speleoarchaeological excavation operations (setting up a georeferenced coordinate system in the cave). The digital twins of MArTA's artifacts were created to be integrated into a webGIS, for scientific and educational purposes, developed by Arc-Team for the Taranto museum.
SLIDE 40
Conclusions: the only technique that allowed obtaining 3D (digital twins), acceptable according to Archaeological Tolerance, in all these cases was SfM. Any technique set up on different hardware has failed in one or more cases.
SLIDE 41
Among the most difficult objects to 3D document during the MArTA experience were the two monumental red-figure kraters (one attributed to the Painter of Carnea and the other to the Painter of the Birth of Dionysus). These artifacts, also due to their size, were not movable and were photographed through the glass of the display case, of course, taking care to eliminate ambient light as much as possible (also due to the large extremely reflective black varnish surfaces).
SLIDE 42
The 3D model shows the final result, while the photos on the right show the forced camera shots (green points).
SLIDE 43
Another of the most complex objects to document at MArTA was a small (working!) ceramic nymphaeum. For reasons of Archaeological Tolerance, it was extremely important, in this case, to document both the exterior and interior of the object, despite its small size. Only in this way could the functioning of the artifact be shown, which, through a small external tank, filtered water internally to then spout it from a small internal lion protome.
SLIDE 44
The internal documentation of the ceramic nymphaeum was possible only through SfM techniques, as no tool, outside of a small camera, could be inserted through the openings of the artifact (of very small dimensions). The image shown here is a 360-degree shot of the inside of the nymphaeum.
SLIDE 45
Thank you for your attention!
I hope that this presentation can be useful. Have a nice day!
