Hi, we’re Factum Foundation for Digital Technology in Conservation, a non-profit working to record cultural heritage artefacts at the highest possible resolution. Where 3D models sometimes serve mainly to give an overall impression of an object’s appearance, our models seek to replicate every detail of its texture and material composition, encouraging close looking and sustained analysis. Since our foundation in 2009, and before that under the aegis of our sister company Factum Arte, we’ve recorded artworks, objects, and buildings ranging from Egyptian tombs to Renaissance paintings to monumental Assyrian sculptures.
Inputs and Outputs: From Digital Models to Physical Facsimiles
To make these recordings we use structured light scanners, our own Lucida 3D Laser Scanner (designed by artist and engineer Manuel Franquelo with support from Factum Foundation), and photogrammetry. We spend a lot of time comparing different recording systems and developing new ones, and we’re continually exploring ways of recording tricky, reflective materials such as marble and metal. We’ve found that photogrammetry is one of the best techniques for recording these difficult surfaces, and although this technology is often associated with very imprecise models, Factum’s methodology for it gives results that can be accurate to 100 microns—on a par with structured light scanning.
All of our recordings are made at a resolution high enough that the object could, in theory, be reproduced as a facsimile: a physical copy which to the naked eye is indistinguishable from the original. Very often, we actually do go ahead and make facsimiles based on our scans, often by 3D-printing or CNC-milling the processed scan data and then transferring the results into other materials using processes such as plaster casting.
But 3D digital models can also be an endpoint in their own right, allowing objects to be seen and manipulated by a much wider audience than would have access to the original. Factum Foundation’s models are used by conservators, scholars, and the general public to examine hard-to-see objects, and have been shown in exhibitions across the world. They can also function as a ‘condition report’ for the institutions which hold the originals: they offer a definitive record of an object’s state at a particular point in time, which can be referred back to in the future to check for deterioration or other changes to the work.
Recording in Miniature: The Jamnitzer Bell
Each object comes with its own recording challenges, and particular models can be used and understood in very different ways by audiences. In the case of a silver bell by the 16th-century goldsmith Wenzel Jamnitzer, it’s actually very difficult to look closely at the original even if you’re standing in front of it. Although only 13cm high, the bell is literally crawling with life: lizards, insects, and garlands cover every inch of its surface. But the reflective sheen of the silver confuses both the eye and the camera, with both having to work hard to create an accurate image of the object.
In order to prevent the glare from the silver distorting the photogrammetry data, Factum Foundation ended up recording the bell twice: first, we took long exposures on a tripod (using a Sony A7RII with a Zeiss 55mm F1.8 lens, and a Sony G Macro 90mm F2.8), and then we repeated the recording using a cross-polarised lens to suppress glare (we used a Canon 5DSR, a Sigma 50mm lens, and a Yongnuo mounted flash). The two datasets, 1400 images in total, were then combined in post-processing. The result is a 3D model that can be rotated almost as if you were holding the object in your hand. The data was also used to ‘re-materialise’ the bell as a facsimile.
Recording the Monumental: The Sarcophagus of Seti I
In contrast to the Jamnitzer bell, the sarcophagus of the Egyptian pharaoh Seti I wasn’t designed to be looked at at all—its makers intended it to be interred in an underground tomb for eternity. For over 3000 years Seti’s mummy stretched full length over the carved alabaster form of the sky goddess Nut, surrounded by scenes depicting his passage through the underworld. But following excavation in the Valley of the Kings in the early 19th century the sarcophagus was sold in London to Sir John Soane, and it is now the pièce de resistance of Sir John Soane’s Museum.
In 2016, Factum Foundation worked with the museum to create a digital model of the sarcophagus for an exhibition. 4500 photographs were taken over the course of a week in the museum’s ‘crypt’, and processed using RealityCapture into a model made up of 2.7 billion polygons (simplified to 1.5m for display on Sketchfab). It’s a model with multiple purposes: it allows curators at Sir John Soane’s Museum new ways of looking at one of their most extraordinary holdings, it has—again—played a role in the process of constructing a facsimile, and it allows those who can’t travel to London, whether scholars or the general public, to inspect up close a priceless part of the cultural heritage of Egypt and of the world.
The Future of Photogrammetry: Training in Jeddah With Art Jameel
3D models also allow us to make records of fragile or threatened heritage—and to share these skills with those whose own heritage is directly at risk. In 2017, together with project partners Art Jameel, we ran a training program to record architectural elements of Al-Balad, the old quarter of Jeddah in Saudi Arabia. Twelve students, all women, from the Jameel House of Traditional Arts learnt how to use photogrammetry to record the intricately carved wooden doors and gypsum façades of the city’s historic buildings, and how to process the resulting data with RealityCapture. The models were then uploaded by Factum Foundation and Art Jameel to Sketchfab, where they serve as a lasting record of the city’s rich architectural history and also as an inspiration and aid to the students at Jameel House of Traditional Arts, who are learning the skills to repair and remake these artworks and keep the city’s decorative tradition alive.
Digital Restoration and Digital Sharing
These examples are only a handful of the ways in which Factum Foundation uses 3D recording and modeling. For some projects, we merge high-resolution photogrammetry or structured light scans of an object with a lower-resolution LiDAR scan of the space in which it’s located, making it possible to visualise the object in its original architectural or landscape context. In other cases, working closely with art historians and museum conservators, we conduct ‘digital restoration’ on sculptures and buildings: filling in on the digital model the cracks and gaps which are present on the original, or digitally reassembling a fragmented sculpture from its scanned parts. Over the last couple of years we’ve also been using aerial photogrammetry to create models of spaces and objects which can’t be adequately recorded from the ground. Wherever possible, we release all of our models and data on an open-access basis.
Sketchfab is an amazing resource for us: as well as letting us share simplified versions of our models with a wider audience, it allows us to see how other people are using 3D scanning and modeling to record cultural heritage. One of our favourite models on the site is this one of a 4th-century Roman hunt mosaic from Piazza Armerina, Sicily, by Global Digital Heritage. Mosaics are inherently fragile, and it’s often difficult to see their details without walking over them, so models like this transform the ways in which we can experience them. The 3D model allows you to move from episode to episode of this complex scene, and even to get up close enough to see each individual tessera. Mosaics, which are often either reburied or removed from their original contexts into museums soon after excavation, are an art form that can really benefit from 3D recording, with digital models constituting a vital archaeological record of the condition and location in which they were found.
Recording methods like photogrammetry and white-light scanning are already increasingly in use on archaeological excavations, and it seems likely that in the future, the on-site creation of 3D models will be standard practice throughout the profession. Factum Foundation is delighted by the wide uptake and application of these techniques by museums and universities, but we also believe that in a time of swift technological change it’s vital to reassert the importance of scanning in detail—of making records which accurately mimic the texture and surface topology of the world around us, and which stand the test of close viewing.