Hop on board as we continue our journey Around the World in 80 Models! We began our itinerary at Sketchfab headquarters in New York and are working our way through Europe, Africa, Asia, Oceania, South America, and North America. To catch up on past destinations, check out the rest of the Around the World in 80 Models series.
This week we leave Europe and arrive in Africa! Our first stop is Mali, where art enthusiast and medical radiologist Marc Ghysels uncovers the secrets of a centuries-old terracotta.
Djenne Region, Mali: Djenne Terracotta
My name is Marc Ghysels and I am a medical radiologist.
One of my interests outside the medical field is ancient sculpture. Fifteen years ago, I set up a company in Brussels that uses an X-ray scanner to assess the authenticity of antique sculptures.
At the end of 2015 we had just discovered Sketchfab and were keen to see how we could use it to make an electronic Christmas card for our customers.
We soon saw that the PhotoScan app (by Agisoft: Standard Edition, version 1.2.3) was the best solution for what we wanted, but we needed to find an object to make an appropriate 3D model, that is, related to our professional activities but not too complicated for a first experience with modelling.
We picked an archaeological terracotta sculpture from the Djenne region in Mali (13-17th century), which we had just put through the scanner to appraise it before a sale.*
In fact, the figure was unearthed during clandestine excavations in the 1980s. Nothing is known of its history or context. Although it was shown to the public in the 1990 exhibition “Terra d’Africa, terra d’Archeologia” at the French Cultural Centre in Rome, it remains a mystery. We are reduced to guesswork, particularly about the snakes and abscesses all over the poor woman’s body.
The scan told us one thing at least: the object was certainly not, as was sometimes suggested, a funeral urn. The scan showed no sign of any bones or a proper opening; just soil and a few bells made of baked clay. The sculpture proved to be completely hollow. The spherical cavity, now largely filled with sediment, is pierced by one small hole in the left side of the figure (see the pink arrow on the slice below):
The hole is only a centimetre in diameter, which proves that the bells, some of which are larger than the hole (pink arrowhead), were put inside before the statue was fired and so are an integral part of the work. All the same, far be it from us to suggest it was a maraca!
The sculpture was suitable for our modelling project because:
it was easy to handle (30 cm diameter; 15 kg),
it had numerous decorative elements all over its surface which could not be illustrated exhaustively in one or two photographs, so 3D imaging was particularly pertinent,
the terracotta surface did not cause awkward reflections, even under spotlights (reflections can cause mis-registration in PhotoScan calculations),
its globular form made it easy to fit inside a virtual Christmas bauble,
it was a direct echo of the article “Scrofulous Sogolon” that we had published a few months before.
Six series of photographs were taken with a Canon EOS 5D Mark III camera equipped with a Canon EF 24-105 mm f/4L IS lens. The sculpture was turned by 12° after each photograph.
This photo shows the ascending or descending camera angles of the first photo in each of the six series of 30 photographs:
Four devices were used to speed up shooting of the 180 photographs:
A neutral grey background to facilitate the use of Magic Wand when selecting parts of photographs imported into PhotoScan,
A turntable on a ball bearing base:
three umbrella lights: two above and one below the object to give the evenest possible lighting without eliminating all shadows,
for the camera: a robust studio stand for shake-free shots (camera and lens settings: 80mm – f/16 – 0.6s – ISO 200 – 3840 x 5760 pixels).
After about three hours spent post processing the data in PhotoScan running on an Apple iMac 27″ 5K, the 3D model was ready to be exported to Sketchfab.
From there it was put, virtually, with a hyperlink, inside a transparent Christmas bauble using Adobe PhotoShop:
Encouraged by the compliments from our customers, we went on to make other 3D models of sculptures, this time working not from photographs but from VRT (Volume Rendering Technique) images generated after other scans. You can see a few of our non-confidential models on Sketchfab.
P.S. this first positive experience left us with just one tiny regret that we did not photograph the base of the sculpture where it touched the turntable.
* : by the way, Sotheby’s New York has just sold another Djenne terracotta sculpture for a mind-boggling $ 790,000.
To see more of Marc’s models here on Sketchfab, check out his profile!