Emphasising Inscriptions Using 123D Catch

One of the most interesting projects I have been working on over the past few months has been trying to emphasise inscriptions on artefacts using Photogrammetry. The theory is that if the model is accurate enough it should be possible for a program to determine the different bumps in a surface and exaggerate them in order to make them easier to identify.

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My first attempt was with a lead stopper (of which I have posted before), which appeared to have some form of writing inscribed on its surface. Having made a model using 123D Catch, I run it through Meshlab and tested many different filters to see if any of them gave me different results. One in particular seemed to do exactly what I wanted, changing the colour of the texture based on the form of the surface. This is the Colourise curvature (APSS) filter, with a very high MLS (I went for 50000) and using Approximate mean as curvature type. he results were some form of inscription, clearer than the photographs, but still quite murky.

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In addition to this scarce results, other tests with different artefacts pointed towards a lucky coincidence rather than an actual method.

One of the main issues I was also having was that Meshlab kept on crashing when using certain filters or shaders, which meant I could only test out only some of the possible options. So when I made a model of a series of modern graffiti at Cardiff Castle the results were also deluding.

The other day though I so happened to update my Meshlab program, as well as bumping into this interesting article, which gave me the exact solution I was looking for http://www.dayofarchaeology.com/enhancing-worn-inscriptions-and-the-day-of-archaeology-2012/

One of the shaders that I had tried using but that crashed every time was the Radiance Scaling tool, which does exactly what I was aiming to do. I run the graffiti and the results are amazing. The original model stripped of textures is a very unclear blurry surface, but after Radiance Scaling the graffiti come to life. The exact mechanics behind this tool, and hence the accuracy, are currently something I am working on, but at least visually the results are there.

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If this proves to be an effective method, it would suggest that Photogrammetry is not simply technology for technology’s sake, but it can actually be used to interpret archaeology in ways not available before.

Edit: I’d also like to draw attention to the fact that this model was made entirely using my iPhone.

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