3D artefact recording part one

45 degree capture

This series of blog posts, in combination with the blogs of my fellow MAs Richard Breen and Aveen Holland, will unpack the methods, technologies, challenges and results of our AFF622 group assignment.

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Scenario

My colleagues and I were asked to examine, record and publish various artefacts which had been found at the abode of an alleged looter. We were tasked specifically to deliver as much three-dimensional information from the objects as possible, while highlighting any special features or peculiar characteristics. To do this we considered and ultimately employed a variety of technologies and methods which had been demonstrated to us during the first semester in our Digital Heritage module.

A broad note on challenges 

Each technology provided its own challenges, as did the artefacts themselves, as well as the dynamic of group work within a busy academic setting. The methods themselves were often tedious and somewhat finicky by virtue of their demand for high degrees of accuracy and their reliance on technologies that themselves required patience and deliberation.

The nature of group work, where there is many voices, in this case all novice, often added to the length of deliberation and the tedium. This said, my colleagues were good natured and thoughtful throughout the processes and if anything, the group paid, in the form of time, for an obstinate commitment to democracy and equity. I think we would each agree than the virtues of hierarchy were manifest at times but rarely trumped the virtues of fairness and plurality. If an individual may learn from their mistakes then it follows that a group can learn a great deal more and also profit from the consolation of camaraderie. In that spirit, I would like to thank both Aveen and Richard for their patience and doggedness.

Best laid schemes… 

We began to plan our project in a private study room in the library. Calendars were filled in and timetables were drawn up and, although the project seemed quite daunting when viewed in the company of the other course work, the effort to put a shape on it seemed to make it manageable. Each artefact was considered individually and prescribed what we felt were the appropriate methods to effectively capture their characteristics.

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On the heels of this a date was set to begin capturing images and we considered it reasonable to think that we could have the photographic capturing done for both RTI and photogrammetry (more of which shortly) achieved in one or two sessions. Needless to say, this would not be the case.

Tentative steps 

We decided to start with R.T.I. or Reflective Transformation Imaging, a method that uses specialist software to combine images taken of an object under various light conditions that are controlled by accurately changing the angle of the light source before each image is taken. This method captures surface detail by highlighting it through the movement of shadows and light. The software estimates the position of the light source based on its reflection on two shiny spheres that are along side the object. It then aggregates the images into one project file that can be manipulated to give the impression of moving light over the static object. For this reason both the spheres and the object must be totally static throughout capturing and the movement of light should be deliberate and consistent to allow for effective control in the viewing software.

We decided to capture the surface detail of the two sides of the Greek coin, the papyrus and the painting. The size of the coin made it an obvious candidate for R.T.I. as well as its condition while details on the painting surface such as finger prints and paintbrush hairs convinced us that it also warranted this method. The papyrus had quite a lot of contour and coarse detail that we thought needed to be captured to accurately record its physical nature which suggested R.T.I. was the best method for it too.

Each artefact delivered its own challenges here. The papyrus needed to be kept relatively flat to make a useful model as it had been scrolled and constantly wanted to roll back up. Various solutions were considered including weights and pressing. Of course the conservation of the artefact was most important and a small amount of pressing combined with meagre amounts of tack around the edges was deemed to be the most effective way to keep it flat and still without causing damage.

The size of the coin required very small spheres to be used so they would not cast shadows over the artefact while the height of the painting canvas caused the opposite problem where the artefact tended to cast shadow across the spheres. These issues were predicted and avoided however.

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For a  more detailed description of the R.T.I. capturing process, including camera set up, as well as the software procedure, Aveen Holland has a detailed report on the process here. To see an example of our delivered products, Richard Breen has the Greek coin R.T.I. embedded on his blogpost here.

This is the first in a series of blog posts which continues here.

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