Thursday, May 13, 2010

Case Study: Rosetta Stone

Ancient Writing Converted to 3D Digital Form

In February of 2008, Joel Freeman of The Freeman Institute Foundation came to Direct Dimensions with an interesting project. Within his collection of historical artifacts, Mr. Freeman owns an original replica of the Rosetta Stone, the famous tablet discovered after Napoleon’s 1798 conquest of Egypt. The tablet bears an inscription of a decree by Ptolemy V circa 196 BC, written in three different languages: two distinct forms of Egyptian hieroglyphics and one form of classical Greek. The Rosetta Stone was so important in the deciphering of some hieroglyphics that the term has come to mean any document or key instrumental in the decryption of a language or code. The original Rosetta Stone has been displayed by the British Museum since 1802, but a handful of first-generation castings were made of the tablet for reproduction.

It was one of these original castings that Mr. Freeman brought to Direct Dimensions. He wants to make scaled reproductions and to help others understand the importance of this famous tablet.

His cast reproduction is full-size, approximately 38-inches tall by 30 inches wide, made from black resin with the critical lettering inscribed on the flat front face. Because it is only a face casting that is two inches deep, this posed another problem, as he wished to make an accurate replica measuring the same 11-inch thick as the original tablet.

After consulting with the engineers at Direct Dimensions about the project and understand how Mr. Freeman intended to actually fabricate the piece, it was decided that only an extremely accurate 3D digital model of this physical piece could work. The 3D data file would be used to drive a computerized industrial milling machine to carve a highly accurate mold. Direct Dimensions would have to use its most accurate and highest resolution scanning tool to capture the piece.

Over the next several days at the DDI lab in Owings Mills, the cast replica was digitized using a non-contact laser line scanner mounted on a motorized precision coordinate measuring machine, or CMM. This unique scanning system had been integrated a few years earlier by the DDI engineers for projects just like this. With the controlled motion of the CMM combined with the scanner from Kreon Technologies, this system can achieve resolutions approaching 25 microns. This translates to 3D point every one-thousands of an inch (0.001”) - a dot per inch resolution sufficient for capturing even fingerprints in 3D.

The resulting massive point cloud file was so detailed that when processed into it a 3D mesh weighed in at over 10 million polygons. A figure, according to project manager Peter Kennedy, “that definitely strained the limit of our already extensive computing power.”

In addition to the precise scan of the tablet’s front face, a model incorporating the tablet’s true thickness had to be created. With standard photographs and other reference materials provided by Freeman, the digital modeling team at Direct Dimensions used a variety of software products, including PolyWorks, Geomagic, and Z Brush, to digitally sculpt the shape and contour of the original tablet’s back side. The back was then combined with the precise data from the front to complete the high accuracy digital model of the real Rosetta Stone.

The final deliverable in polygon format will enable Mr. Freeman and his other collaborators to mill the completed replica molds. He aims to use his replica as a centerpiece in his educational programming, to be housed in an exhibit in the Black History galleries of The Freeman Institute Foundation.

If you are interested in learning more about the Rosetta Stone or owning a full-size, 3D replica, please visit