The hunt for the digital Unicorn

In 1992, I read an article in the New Yorker magazine about two mathematician brothers, David and Gregory Chudnovsky, who had built a super computer in Gregory's apartment from mail order parts. They had built the computer to calculate the value of pi out as far as possible.

In the new issue of the New Yorker, there is another article about the brothers, now employed in a research institute, consisting of the two of them alone, in the Polytechnic University in Brooklyn.

The subject of the article was the effort by the brothers to piece together a large number of digital images of a set of medieval tapestries. In 1998, restorers worked on seven 12 by 14 foot tapestries dating from around 1500, woven on the theme of the "Hunt of the Unicorn." Priceless and beautiful, the tapestries were photographed at the time by a team of photographers working with a large digital camera on tracks, scanning the large tapestries, one small area at a time. The idea was to piece together a mosaic master image of each tapestry, using computer photoprocessing software. There wasn't a computer or software equal to the job. Enter the brothers Chudnovsky.

Eventually, many billions of calculations of digital manipulation of each pixel in relation to adjacent pixels had to be done. It turned out that in the process of moving the camera many times for each series of photgraphs, tiny changes in the arrangement of the tapestries came about.

The analysis and correction took prodigies of programming. The brothers used their latest homebrew supercomputer, named only "It," resting on racks improvised from frames and screens purchased from Home Depot. Each tile had to be analyzed, relating it to the others. Concentrating on the last, most crucial of the tapestries, in twenty-four hours of processing the individually corrected images were joined together.

One of the seven tapestries, the final, climactic scene, was captured digitally in its entirety. It is unclear whether there is the will, money or time to complete all of the tapestries.

Da Link. (This page also has a link to the original 1992 article about the brothers. Well worth the read.)

These two articles are really an epic of mental exploration by two more than Über Geeks.