Software squeezes 3D dataBy Eric Smalley, Technology Research NewsData compression algorithms  the mathematical formulas that shrink digitized video and still images into packages small enough to travel over the Internet  have arrived in the world of 3D graphics. Researchers at the California Institute of Technology and Lucent Technologies' Bell Labs have adapted an image compression algorithm to handle the complex geometries of virtual threedimensional objects. The 3D compression algorithm can be used to transmit ComputerAided Design (CAD) files and digitized scans of reallife objects over ordinary Internet connections. The technology could allow consumers to download 3D renditions of things like furniture and appliances and suppliers to host 3D catalogs of mechanical parts on the Web, said Wim Sweldens, a research staff member at Bell Labs. The 3D compression algorithm is based on wavelets, which are mathematical formulas that analyze electrical signals. Wavelets analyze the frequencies of a signal at different time intervals. "We generalized the idea of wavelets [to] make it work on more complicated geometry," Sweldens said. "Most of the standard wavelet technology is really suited for very simple geometries. An image is essentially a square or a rectangle. The image may be very complex but the geometry is very simple." The CaltechBell Labs algorithm is 12 times more efficient for compressing 3D graphics than MPEG4 compression, which is designed to compress video, Sweldens said. Eve Riskin, an associate professor at the University of Washington and codirector of the university's Data Compression Laboratory called a new algorithm "a neat piece of work," noting that the upcoming JPEG 2000 standard for still image compression is also based on wavelets. The 3D compression algorithm both shrinks the number of bits needed to represent a 3D object and orders the bits so that only the first portion of the postcompression file is needed to provide a lowresolution version of the object. The more bits that come through, the sharper the image becomes. In one example, the form of a 3D object is recognizable after 956 bytes, which is less than four percent of the total compressed data. Much of the detail is recognizable after 4,806 bytes, or just over 18 percent of the data. (See image.) This also allows one 3D data file to be transmitted to computers that have different 3D graphics capabilities, Sweldens said. This is possible because 3D objects are actually made up of many tiny polygons, usually triangles, of various sizes and shapes. "It doesn't exactly matter where these triangles are as long as their shape overall represents the original piece of geometry. One very crucial aspect of our algorithm is that we take [near] optimal advantage of that degree of freedom." This type of compression also improves the algorithm's performance. "Compression technology invariably uses some type of prediction," said Sweldens. The algorithm optimizes the layout of the triangles to make their locations easy to predict. "The more accurate the prediction method the less information actually has to be transmitted," he said. The algorithm is ready for widespread use, Sweldens said. "There's nothing much holding it back technologically," he said. The team is working on extending the algorithm to work with 3D geometry combined with textual data, and animation. The team's work was funded by Lucent Technologies, the National Science Foundation, the David and Lucile Packard Foundation and the Alias Wavefront subsidiary of Selected Graphics, Inc. Timeline: Now Funding: Government, Corporate, Private TRN Categories: Data Structures and Algorithms Story Type: News Related Elements: Graphic Advertisements: 
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