In August 2015 I was commissioned by National Maritime Museum Cornwall to produce a 3D printed replica of the late medieval bench end in the church of St Senara in Zennor. It depicts a mermaid, which is famously known as the Mermaid of Zennor. This has, along with another medieval bench end, been incorporated into a seat called the "Mermaid Chair". The replica was for an exhibition entitled "Mermaids: Women at Sea" highlighting the achievements of female sailors. Naturally, people would expect to also see a mermaid - a legendary woman of the sea - as part of the display.
The concept was to produce a half-size replica, which would be mounted upon a large photograph of the church interior. The 3D print would be positioned exactly over the portion of the photo occupied by the original - a collage of 2D and 3D. Visitors would be encouraged to touch the exhibit - something that should not be encouraged with the original medieval frieze.
Before any work was undertaken, we sought permission from the churchwardens. They were keen to hear about the capture methods and learn more about the exhibition, and kindly gave us the go-ahead.
I used photogrammetry - a form of 3D capture that uses photographs - to capture the entire bench-end. Using natural light only a tripod was necessary to compensate for the long exposure times. Before commencing the capture I planned my visit with advice from the churchwarden, when there would be no direct sunlight pouring in through the stained glass. This is essential for correct colour capture, pretty as that may have looked.
There were many challenges with the capture in-situ in the church. Aside from technical challenges, St Senara is a well-visited church, and everyone wanted to see the mermaid. And to find out what I was doing. So it took a little longer than I had hoped, as it is always good to explain what's going on to curious visitors, but the results turned out very well indeed.
The resulting model consisted of tens of millions of measurement points which were used to create a highly accurate and 'watertight' 3D model. Given that the rear of the mermaid bench-end would be fixed to a display panel, the model was altered to create a smooth plane on the reverse to aid mounting. After preparing the model for 3D printing (checking the model for errors that could confuse a 3D printer) the data was sent to ThinkSee3D for printing. The resulting replica would be half actual size (182mm x 380mm x 20mm) - full size (370mm x 755mm x 40mm) would have been prohibitively expensive and would need to be printed in two parts then glued together. It would be printed in full colour using a solid gypsum-based resin.
After some small test prints and experiments with colour, and a coat of varnish to replicate the finish of the real medieval wood, the finished 3D replica of the Mermaid of Zennor was ready. Museum staff mounted the print carefully over one of my photos - the result was rather effective!