CURVE

Collaborative University Research & Visualization Environment

Author: Spencer Roberts

Larger-scale Photogrammetry at CURVE

During the spring semester, I acquired a clay whisky jug from the Phoenix Lab, which contains artifacts recovered from the excavation of MARTA lines in the 1970s. Dr. Robin Wharton has worked with students in her multimodel composition course to scan and model objects from the collection, and discussed the process in Atlanta Studies. In this case, the purpose was to experiment with photogrammetry for larger objects, testing the equipment and software that the Library has acquired. The jug is roughly 8 inches high and 6 inches in diameter, with a circumference of 19 inches.

image of whisky jug

Whisky Jug

The jug wears the story of its life. The outside is worn and pitted, and carries a few kiln drips, where the kiln bricks melted and dripped on to the jug as it was fired. These drips show as dark splotches on the outside of the jug. Stamped on the top shoulder of the jug are two names: T.W. Cofield and E.C. Brown.

Whisky jug with stamp showing T.W. Cofield and E.C. Brown

Stamp showing T.W. Cofield and E.C. Brown

To capture the entire jug in detail, I took images of the jug at 15 degree intervals on three elevations. I used Agisoft Photoscan to assembled the images into point clouds, meshes, and then textured models. I then pinned the three partial sections together, which resulted in a full model of the jug.

In the finished 3D model, you can manipulate the jug to see its details and textures, including the stamped inscription with the two potters’ names.

Click here to see the Whisky Jug on SketchFab

Thomas William Cofield and Edward C. Brown were cousins who lived in the Howell’s Mills area in northwest Atlanta, near present-day Buckhead. Edward’s father was Bowling P. Brown, a potter. His grandfather was Bowling Brown, also a potter, who had moved the family from Jugtown (an unofficial name) on borders of Upson and Pike counties.

Bowling’s daughter (and B.P.’s sister) Mary Jane Brown married Thomas B. Cofield from North Carolina while they lived in Jugtown. Their son, Thomas W. Cofield, became a potter and worked alongside his cousin, E.C. Brown, to produce jugs for Atlanta’s businesses from the 1880s through the 1910s. [Note 1]

In his history of Georgia’s folk pottery, John A. Burrison suggests that Thomas and Edward worked together no later than 1911, after which Edward “became a gardener (and later foreman) at Grant Park.” Based on this suggestion, we can infer that the whisky jug is at least 106 years old. The jug is in remarkable shape for its age, but I still wouldn’t recommend drinking from it.

 

Notes

  1. John A. Burrison, Brothers in Clay: The Story of Georgia Folk Pottery (Athens, GA: University of Georgia Press, 2008), pp. 71, 168, 191, 195, 199.
  2. Ibid., p. 195.

[This article has been cross-posted from swroberts.ca]

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Photogrammetry at CURVE

Photogrammetry, for the purpose of our work at Georgia State, refers to the use of software to combine, convert, and render 2D images into a 3D object. There are numerous methods for this practice, ranging from a single camera operated by a moving human to complex arrangements with multiple cameras and a movable object. The process can capture a range of objects from extremely large to fairly small. For instance, you might capture an ancient ruin by taking photographs as you walk around the structure. You might also capture a small figurine by taking photos with your camera or phone. The process changes depending on the size of object, the equipment available, and the software used.

In the spring semester, the library and CETL are prototyping a 3D scanning/modeling/printing course, in which students will learn how to fully digitize and replicate a material object in both digital and physical forms. To facilitate their learning, we have acquired a photogrammetry kit that will complement the other equipment we have available in the library.

The kit includes:

  • One Canon Rebel T5i DSLR camera, with standard 35mm lens
  • One basic tripod with multi-axis pan and tilt functions
  • One turntable, modified with degree markings
  • One wireless camera remote

To test the kit, I selected a small owl figurine. The object is roughly 1.5 x 1.25 x 1.125 inches. I placed the object in the center of the turntable, facing the 0 degree marker. I aimed the camera directly at the object on a level horizontal plane. Using portrait settings, the internal camera flash, and the wireless remote, I took photographs of the object at 15 degree increments, for a total of 24 images. I did not capture the top or bottom of the object for this test. Total time for capture: 20 minutes.

Using Agisoft Photoscan, which is available on four of CURVE‘s workstations, I aligned the photos, generated a cloud of points, created a mesh, and then textured the mesh. I removed some unnecessary details from the model, and then exported as an .obj model. I uploaded the model to SketchFab. Total time for model creation: 20 minutes.

Admittedly, the model lacks some features, such as a true representation of the bottom and top of the figurine. For a quick 40-minute test, however, the kit and software worked very well. For smaller objects, we may need to acquire a macro lens for the camera. The primary use of this equipment will be to train students, which will provide an additional benefit of helping to preserve archival objects and provide access to objects that are fragile or inaccessible.

Students interested in using this kit should contact me to arrange a meeting.

See below for a 3D rendering of the model and photos of the kit.

Original Figurine and Final 3D Model

Owl Figurine

Owl Figurine

Photos of the Kit

Photogrammetry Kit

Photogrammetry Kit

Canon Rebel T5i

Canon Rebel T5i

Turntable with degree markings

Turntable with degree markings

Wireless shutter remote

Wireless shutter remote

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