Monday, September 21, 2009

Wrestling with 3D

With Kelley out of town, cataloging is on hold and I am learning some new skills. Today I took a sherd from a tin glazed punch bowl (top) and turned it into a complete 3D image using AutoCAD(bottom).

The first step in the process was to create an accurate drawing of the sherd (center). Using a radius template, I found the radius of the bowl rim and the foot-ring. I measured the height as well. I then sketched the outside and inside of the bowl using these measurements and a mixture of tracing and freehand. I also free handed the painted decorations as best I could. The drawing was scanned onto the computer and imported as a 'raster image' into AutoCAD. From there I had to trace the imported image so I had a series of lines and points that could be manipulated. I made the surface of the bowl with decorations and the profile of the thickness of the bowl separate images.

AutoCAD took the profile and swung it around 360 degrees on its center axis, like drawing a circle with a compass. Add a surface rendering and there was a three dimensional image of the punch bowl as it would have looked in its entirety (without decorations and surface variations). I moved the traced decorations into place on this image and voila! Finished!

Of course in recounting this process, I have glossed over all the erasing, undoing, head-scratching, and computer defenestration. But with help from Jim, I am quite happy with the results. I will continue to tweak the image and whose knows where it will eventually end up?



Jim said...

Eventually we will post interactive 3D images of artifacts on a website.

Reconstructed objects in three dimensions can have analytic value. For example, we can calculate volumes from fragmentary glass and ceramic vessels as long as we have a continuous base to rim profile. We might then look at stoneware beer mugs from an inn or ordinary site: did they hold the legally mandated volume?

We can also examine and illustrate the vessel forms used at one site and compare them to another. For example, archaeologists have noted that poorer households tended to eat stewed meals that used whatever foods were available and that did not require much attention while simmering, whereas wealthier households tended to cook individual portions. Those observations have been based on meat cuts, as represented by butchered bones, and by the different ratios of plates to bowls on a number of 18th and 19th-century sites.


Jim said...

PS. Click on image for a larger, clearer view.