Thursday 19 March 2020

In June 2019 I was part of an exciting project to produce an exceptionally accurate and high-resolution 3D scan of the Ashes Urn.
This was partly motivated by the Ashes Urn leaving its home at Marlebone Cricket Club, going on loan to State Library Victoria in Melbourne.
After several weeks of testing on a facsimile Urn, the Ashes came to The Postal Museum Digitsation Studio. I then had two days to capture it using Photogrammetry.
The challenge of creating a small and perfectly formed model really appealed to me - the small size, variable texture and glossy surface of the Urn all presented challenges for the capture.
The photographs were all made using a Phase One XF IQ3 100, which provided incredible resolution, but more importantly the XF's built-in automatic focus-stacking feature. Every 'single' photographs used to make the model was in fact made up of many many photographs; this meant that the entire urn could be captures entirely in focus with no issue of depth of field. All in all I made 6,146 photographs of the Urn over two days.
The next challenge was getting good surface geometry; being a highly-glossy ceramic object with rounded sides it was impossible to capture without some kind of specular reflections which would decrease the accuracy of the geometry and reduce the accuracy of the colour and tonal capture. The solution to this was to capture a mixture of very soft light photographs and some cross-polarised photographs. This mixture of normal reflected-light and reflected light photographs would then be aligned in Reality Capture and then certain aspects of the model were then made from either the normal and cross-polarised images, along with a bit of masking.
Thanks to Martin Devereux, then Head of Digital at The Postal Museum for all of the post-production work, especially masking images and batch focus-stacking. Thanks to Thomas Flynn of Sketchfab for making a roughness map and his help rendering the final object file. Huge thanks to the team at Marylebone Cricket Club for entrusting me and The Postal Museum Digitisation Studio with capturing the Urn.
You can read the full story on The Postal Museum blog here:

The facsimile of the Urn (MUCH less glossy than the real thing) captured with normal reflected light on the left, and cross-polarised light on the right.

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