# 3D visualisation of fourth-century Christian monuments and archaeological sites of Egypt

Victor Ghica, Mohammed Abdelaziz

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## To cite this version:

Victor Ghica, Mohammed Abdelaziz. 3D visualisation of fourth-century Christian monuments and archaeological sites of Egypt. Ancient Egypt, New Technologies. Proceedings of the International Conference, 2nd edition, 5-7 July 2023, University of Naples 'L'Orientale', Dipartimento di Asia, Africa e Mediterraneo (DAAM), Università degli Studi di Napoli L'Orientale, Jul 2023, Naples, Italy. hal-05308858

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https://hal.science/hal-05308858v1

Submitted on 10 Oct 2025

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Distributed under a Creative Commons Attribution 4.0 International License
3D visualisation of fourth-century
Christian monuments and archaeological sites of Egypt

Victor Ghica, Mohammed Abdelaziz

This short paper concentrates on the 3D data visualisation component of one of the work-packages of the ERC-CoG project DEChriM (“Deconstructing Early Christian Metanarratives: Fourth-Century Egyptian Christianity in the Light of Material Evidence”). Building on numerous field operations geared towards acquisition of archaeological data and supported by a massive repertoire of archaeological sites, DEChriM produced two databases, which have been opened to the public in September 2021. The first one, 4CARE (“Fourth-Century Archaeological Record of Egypt”), is a GIS-based gazetteer of archaeological sites to which extant Christian material, mobile or immobile, is associated. The various types of metadata used as descriptors for each individual archaeological site incorporated in 4CARE include also photogrammetric models, which we produced for about half the sites of the database. What we are presenting here is the workflow our team developed for the 3D models – both photogrammetric and 3D architectural reconstructions – embedded in 4CARE.

Two quick preliminary notes on the rationale for embedding 3D models in the 4CARE database and the platform chosen for public visualisation. Besides its inescapable utility for off-site studies, our gallery of photogrammetric models represents a very limited and short-term answer to the problem of the preservation and accessibility of archaeological remains. Considered on the backdrop of the wide-spread and fast-paced degradation of exposed mudbrick constructions in Egypt, be it through natural processes, plundering or sheer vandalism, it is our team's desperate attempt to save something of the materiality of the phenomena we are studying. With that goal in mind, our project has been running a good number of field operations throughout Egypt for photogrammetric, and in two cases TLS, data acquisition. With regards to the platform chosen for publishing light versions of our structure-from-motion (SfM) and 3D reconstruction models, we have opted for Sketchfab. Its versatility, cross-platform compatibility, and display capabilities, including VR and AR content, go beyond those of customised in-house built viewers. Additionally, it could be easily integrated into the respective web pages on 4CARE, thus making it an ideal choice for us.

The goal of this paper is to discuss four technical challenges that our project had to overcome: 1. cleaning of sky-noise; 2. merging models from different excavation seasons; 3. blending sharp textures captured in different light conditions; and 4. mixed visualisation (SfM model and 3D reconstruction).

1. *Cleaning of sky-noise*
Because of the diverse types of difficulties encountered there, we shall be using the main structures of the site of Dayr Muștafā Kāšif as the key example. Two key factors compounded the problems that we had to address: the complexity of the architecture (3 floors; preserved height of walls up to 9.6m; numerous enclosed spaces with ceilings in situ; etc.) and the lack of equipment for aerial spatial data acquisition. In order to capture the built surfaces and the terrain, only close-range photogrammetry was accessible to us. Although we photographed the entire monument only from ground levels (without using photography masts or ladders), we obtained a decent photogrammetric model. However, the upper parts of the building required a significant amount of postprocessing. Indeed, because of the angle of the camera photographing from the ground, the number of pixels on the top of the walls was reduced, with extra geometry appearing in the upper parts of the building blended with the sky. Manual cleaning of this parasitic sky-textured geometry was done in Agisoft Metashape and Maxon ZBrush (fig. 1).

<figure><img src="image_3.png" /><figcaption>Fig. 1 Parasite geometry blended with sky, before and after cleaning in Metashape and ZBrush</figcaption></figure>
The removal of the sky-noise results in a loss of points in the cleaned areas on top of the walls. In addition to these gaps, the model featured several holes in the upper floors resulting from them not having been covered by the camera. The solution we adopted was to combine two different pieces of software. Although ZBrush is a valid option, we preferred Geomagic Wrap, which has an excellent tool for closing holes (fig. 2).

<figure><img src="image_4.png" /><figcaption>Fig. 2 Closing holes in 3D Systems Geomagic Wrap (main window) and polygon count reduction in Instant Meshes (bottom left)</figcaption></figure>

After closing the holes and fixing the errors, the polygon-count of the Metashape model hovered around 50,000,000 polygons. To reduce it, one had the one-click solution of decimating the mesh inside Metashape. However, the more advance option provided by Instant Meshes, a software that allows for converting any high-count mesh from triangle to quad polygons, gives the possibility of executing a manual wrapping of the final texture, which provides a smoother visual rendering in a web viewer such as Sketchfab than the automatic decimation in Metashape (fig. 2).

At this stage, the modified 3D model was brought back into the Metashape file for building the texture. Since no cameras captured the top of walls, the textures in these areas were blended with the sky, displaying white and blue colours. To address the issue, we used Adobe Substance Painter, which permits modifying 2D textures on any 3D surface model and where a tool similar to the “Clone Stamp” of Adobe Photoshop allows for erasing the blended textures deriving from the sky-noise and turning them into wall textures.

## 2. Merging models from different excavation seasons

Another frequently performed operation has been the merging of two or more Metashape models from different excavation seasons into one cumulative 3D model. Again, we
are giving here an example from the same site of Dayr Muștafā Kāšif, although we had to deal
with more complicated cases. The first photogrammetric model of the building complex was
captured in 2020. Then, in 2021 and 2022, three areas were excavated in both the eastern and
western halves of the main building (fig. 3).

<figure><img src="image_5.png" /><figcaption>Fig. 3 Metashape models from 2021 and 2022 seasons</figcaption></figure>

The goal was to have Metashape ignore the debris from the model captured in 2021 and accept the area excavated one year later and thus avoid incorrect geometry reconstruction and software confusion. To do so, we used the mask option. In order to ignore the unwanted area, this task was done manually image by image.

3. **Blending sharp textures captured in different light conditions**

If we take the same example from Dayr Muștafā Kāšif, the different Metashape models
of the site that we had created featured different textures, as they had been photographed in
distinct light conditions. We needed then not only to merge the newly excavated areas into the
general 3D model, but also to blend the respective textures of all the models. To do so, we first
performed a manual removal of the area to be replaced with a new model. Then, we used the
Metashape function “Merge by marker”, a tool that allows one to pick up the same feature in the model of each season, by inserting several points. However, after merging the two models in Metashape, they still had to be merged as one single piece to avoid sharp texture edges after building the texture. This second merging was performed in ZBrush, whose DynaMesh tool allows for retopologising the model as a single, new model, although without details. We then used the “Project” tool in ZBrush to bring back the details from the Metashape detailed model. After that, we exported the new model from ZBrush and imported it back to Metashape into the same project, containing now the two merged models. Then we rebuilt the texture again (fig. 4).

<figure><img src="image_6.png" /><figcaption>Fig. 4 2021 Metashape model from 2021 and merged models (2021 and 2022 seasons) imported from ZBrush into Metashape</figcaption></figure>
4. Mixed visualisation (SfM model and 3D reconstruction)

Accessibility and versatility have turned photogrammetric range imaging into a
ubiquitous technique also in Egypt, where Metashape models of archaeological remains of
varying quality proliferate. What has been experimented with far more rarely is incorporating
virtual three-dimensional reconstruction of monuments into SfM models. While a small
handful of workflows have been published,<fnref n="1" /> we will briefly present our own, which was
developed based on the needs of the archaeological sites of Kharga Oasis that DEChriM
studies.

To illustrate our pipeline, we will use again the same site, whose state of preservation
and monumentality present the double advantage of allowing for virtually no unwarranted
architectonic speculation and integrating seamlessly the reconstruction into the
photogrammetric model.

The reconstruction process was based on planimetric documentation produced by our
team, 3D photogrammetric models and spatial analysis. Our end-to-end pipeline consists of: 1.
Agisoft Metashape for SfM model building; 2. 3D Studio Max 2023 for 3D reconstruction; 3.
Sketchfab as a platform for team feedback and visualisation.

Using 8149 images taken with a Canon EOS 5D Mark IV, a high-resolution
photogrammetric model was generated, scaled and geo-referenced. The Metashape model was
then imported, as a FBX file, into 3ds Max 2023, a 3D graphics software that has the double
advantage of incorporating and using the photogrammetric model as a ‘skeleton’ and reference
for reconstructing the architecture to scale, but also of documenting the reconstructed
architecture in colour; this colour coding able to be recorded as a texture in the three-
dimensional space. So, the pipeline rather organically integrates the photogrammetric model
and the reconstructed architectural elements, with the latter virtually reanimating the ruins (fig.
5).

<footnote n="1">¹ See, for example, Fritsch, B., Götz, S., Filser, W., Reinfeld, M., Klose, C., & Vitti, P. (2023). “Mixing Methods: The Use of 3D Techniques at the Ancient Villa of Capo di Sorrento.” *Studies in Digital Heritage, 6* (2), 25–50.
https://doi.org/10.14434/sdh.v6i2.34835</footnote>
In 3ds Max, we divided our 3D reconstruction into different layers containing, for example, walls, ceiling, arches, or stairs, with each architectural category having its own material ID. We then imported the model on Sketchfab using the FBX file format and colour-coded each layer. In addition, since the reconstruction model is unavoidably somewhat crowded, and to allow for a better visualisation of the architectural ensemble, we rendered the colour-coded reconstructed elements transparent (fig. 5).

<figure><img src="image_7.png" /><figcaption>Fig. 5 Semi-transparent colour-coded reconstructed architecture in 3ds Max 2023</figcaption></figure>