3d Printing, Digital Fidelity, and Neolithic Masks

By Chad Hill

Over the last decade it has become increasingly easy to capture high quality 3d data at a variety of scales. Advances in photogrammetry and lower costs for lidar and 3d scanning make it possible for more of the world to be captured and recorded with incredible precision. It has been incredible to watch these technologies permeate the field becoming widely applied tools for documenting cultural heritage. These data are increasingly accessible across the globe. Many museums offer 3d content in their digital collections, archeologists are publishing 3d content in their data repositories or as part of publications, and 3d data platforms are hosting ever increasing quantities of 3d models of sites, structures, and artifacts that are freely available. We are awash in 3d data, but to what purpose?

I’ve long been intrigued by the difference between 3d models of cultural heritage on a screen, and tangible objects that you can hold in your hand. It can be difficult to demonstrate the value of 3d data by showing a rotating object in a PowerPoint presentation that viewers cannot manipulate themselves or even examine closely. I am interested in how we transform 3d models into objects or tangible experiences. One important way is through 3d printing. Although 3d printer technology has existed, in some form, for decades, it is only in the last 10 years that it has become a “mainstream” and more affordable technology. Hobbyists can purchase a 3d printer for a few hundred dollars, and universities increasingly have 3d printers available for faculty, staff, and students, allowing us to make rapid and low cost replicas from our 3d data. However, the most common type of 3d printers, so called “fused deposition modeling” (FDM) printers are not ideal for replication. They print by extruding one layer of plastic at a time, in a single color at a time. The resulting objects tend to have tell-tale layer lines (most commonly between .15 and .3mm thick) and are usually produced in a single color of various types of plastic. Replicas of extremely detailed landscapes or objects are often lacking when printed in mono color plastic, though there are still some great uses for standard home printers.  At the Penn Paleoecology lab, for instance, we built a 3d printed reference collection of pollen grains, primarily from the 3d Pollen Project and with some help from the Penn Biotech Commons, for use in teaching pollen analysis. 

A collection of 3d printed pollen grains, downloaded from the 3dPollen Project, including some printed courtesy of the University of Pennsylvania Libraries’ Biotech Commons

 

I think that the best option for reproducing archaeological data is a different kind of 3d printing:  full colour prints with more advanced machines like “binder-jet” printers. These machines are much more expensive, and thus rare, but produce more realistic prints. An excellent example is the 3d colour print of a neolithic landscape in eastern Jordan, generated from drone data recorded as part of the Eastern Badia Archaeological Project. We produced a 3d colour print of the data and brought it with us so that we could compare it to the actual site in person. I have used similar prints to visualise the looted landscape as part of the Follow the Pots Project in Jordan, to visualise petroglyphs and compare 3d prints to augmented reality, and to recreate hominin footprints at Laetoli, Tanzania as they looked when first excavated in 1978. Unfortunately, these printers are generally either inaccessible or too expensive to use widely.

A Full-colour 3d print of a neolithic landscape in Eastern Jordan 

Most of the 3d printing I do is intended to produce functional parts, rather than replicas, but I try to keep abreast of the novel scientific uses for 3d printing (for instance using 3d printed shell replicas in palaeontology research) and I have spent time thinking about how to utilise standard 3d printers in interesting ways. In the past I’ve tried printing “remixed” models that make replica objects more interactive, like printing famous sculptures converted into 3d building brick puzzles and creating replicas of 3d models as baked goods via 3d printed moulds, including pollen grains, Akkadian cylinder seals, and the Parthenon marbles. One thing I’ve been playing with recently is this sort of “fad” among (non-archaeologist) 3d modellers and 3d printer enthusiasts of creating and printing so-called “low-poly” versions of objects. 3d printable models are built from sets of two dimensional polygons. Even complex and rounded shapes are made from very very large numbers of tiny flat polygons. This popular process of making “low-polygon” models is a trick where you try to reduce the number of polygons to as small a number as possible while still allowing the original shape to be recognisable. Although there are practical reasons for creating low-poly models for digital use (for instance, to improve rendering efficiency in video games), as 3d prints these are just a popular aesthetic style that evokes a nostalgia for early digital objects. For instance, you might take a 3d model of a fox, and reduce the number of polygons until you can still tell it is a fox, but it is made of huge flat polygonal facets. This makes it look like a weird digital artefact from an early video game. Andrew Sink (@AndrewASink) recently published a new online tool for creating these low-poly models and I thought it would be interesting to experiment with it with archaeological data.

A 3d Printed building block puzzle version of a Lamassu from the Palace of Sargon II in the Louvre 

As an archaeologist who works in Israel and Jordan, and on Neolithic materials, I was attracted to experimenting with the 3d model of the Er-Ram Mask in the PEF collection (PEF-AO-4803). This mask is one of only a handful of masks purportedly from the Judean hills and Dead Sea region that likely date to the Neolithic (7th millennium BCE). The collection and display of these masks has been controversial, with most of the masks appearing in antiquities market with no real information on their archaeological findspots. This corpus of material has recently been the center of investigation as part of the Manhattan District Attorney’s probe into Michael Steinhardt, which led to his surrender of 180 antiquities (including some Neolithic masks) purchased dubiously. The mask in the PEF collection was acquired in 1881, when Dr. Thomas Chaplin bought the item from villagers of Er-Ram (Ramleh).

Description of the acquisition of the Er-Ram mask, by Thomas Chaplin, in the Palestine Exploration Fund Quarterly 22, 1890

Although 3d models of most of the Neolithic masks do not appear to be publicly available, a model of the Er-Ram mask has been published on Sketchfab as part of the Micropasts Project.  I downloaded the Er-Ram model, processed it using the LowPoly3d Tool, and printed it on my Prusa Mk3s printer. The two different sized versions took about 8 and 14 hours respectively. I think the result is quite fascinating. You can see that it is clearly the mask, but it also gets this identifiable digital-artifact effect that makes it really obvious it has been manipulated. I believe it becomes a sort of commentary on the limits of digital replication and preservation. This version is not attempting to be the best possible recreation of original, instead it has been intentionally degraded to the point that the loss of fidelity is obvious and the differences from the original are exaggerated. 3d printing cannot produce a perfect replica of an object, and this 3d printed version attempts to highlight and engage with the limitations and goals of 3d printing.e

Two copies (at two different sizes) of a 3d print of a “low-poly” version of the Er-Ram Mask. Amazingly, the dramatic photo on the right was possible because my iPhone identified the mask as a human face and enabled “portrait mode”

Is any of this useful? I don’t know. For several years now, as often as possible, I have tried to bring full color 3d landscape prints with me when I give public lectures about my research with drones. I often pass these around the room when I am speaking. In my experience, maybe half of the people in an audience find it significantly more engaging to have a tangible copy of the data I am talking about in their hands, that they can turn around and get up close to. The other half ask what the point is and seem generally perplexed at why this would be useful. Intentionally manipulated, digitally “degraded” versions of an object might push that boundary even further, but I think there is still something fascinating about holding such an object in your hand and considering the entire process by which it came to be. The original mask was carved, with a function and meaning that we do not understand, broken, discarded, found, purchased, exported, digitized, uploaded, published, shared widely, downloaded, re-processed, and then printed. This is an incredible series of steps, stretching over thousands of years and miles. This version, by highlighting and exaggerating the digital degradation between the original and the replica, is more interesting than a standard 3d print of the model in a single plastic color. It also gives a more visceral experience than seeing the digital model on a screen. It is really amazing.

There remains something important about being able to make these sorts of affordable and easily reproduced replicas: Morag Kersel, who was supposed to be traveling to study the PEF Er-Ram  mask in person, as a PEF-AIAR Fellow for 2020, working on a project entitled “Hidden Histories – the private lives of Levantine Neolithic masks” had to postpone her trip due to COVID-19. I will be sending her one of these masks to hold and look at and show to people in the meantime, until she can access the real object. Although it is not the same, I hope she will be able to use it as part of teaching about the subject and the controversy surrounding these objects.


Note from the PEF: Morag has finally been able to come and do her research at the PEF! Have a look at her recent posts on @PalExFund and  @morkersel

and keep an eye out for more from her on this fascinating subject in the future!

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