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The Trick Is In The Triangles: Speeding Up 3-D Computer Models

February 25, 1998
Johns Hopkins University
A Johns Hopkins computer scienctist has developed software that dramatically increases the speed at which 3-D computer graphics can be put in motion on-screen. A preliminary version of the software is available free on the World Wide Web.

Designers of complex structures -- from toasters to nuclearsubmarines -- often use computers to construct three-dimensionalmodels electronically. But a snag can occur: The more detailedthese models become, the longer it takes to put them in motion onscreen.

A Johns Hopkins University computer scientist has developedsoftware that addresses this problem by significantly speeding upthe way a computer re-displays a three-dimensional model as itchanges position. The program, devised by Subodh Kumar, assistantprofessor of computer science, also gives designers greatercontrol over the level of detail that appears on screen.

Kumar recently posted a preliminary version of the software,called sLIB (short for "surface library"), on the World Wide Webfor free downloading by designers who use the Irix operatingsystem. (A Windows version is being developed.) The program isavailable at:

The secret to Kumar's software, he says, is in how it handlesNon-Uniform Rational B-Spline representations, or NURBS, themathematical shapes that computers can use to depict curvedsurfaces.

A computer can put NURBS together to form a three-dimensionalrepresentation of the complete object. Kumar's new softwarespeeds up this process when an electronic designer is creating orrefining a simple or complex NURBS model.

"This NURBS surface representation is in the computer's memory,"explains Kumar. "It's data, just a sequence of bits and bytesthat you can keep in a file and send to anybody. But how do youbring it back on screen and manipulate it in three dimensions?"

One common technique is to convert the original model intonumerous tiny triangles that, when assembled on the computerscreen, look very much like the original shape. Each time thedesigner clicks a mouse to look at the model from a differentpoint of view, the triangles must be re-displayed in a new way.Kumar's software's streamlines this task by generating far fewertriangles and taking several other technological shortcuts. Theseimprovements, he says, "enable us to speed up the whole processof displaying the NURBS models by better than 100 to 200 timesover the older techniques."

His software also lets a designer zoom in on a particular part ofthe model to continuously increase the level of detail visible atthat location.

While Kumar refines sLIB, he is allowing users of computergraphics systems to download the preliminary version at nocharge. "This provides us with a wide user base to test thesoftware," he explains. "It's not just a simple surface-renderingsystem. It's a whole framework in which you can test your ownideas, plug in your own little piece and see how it behaves."

The Hopkins researcher hopes that his software will someday allowa designer to take visitors on a highly detailed "virtual tour"through the interior of a submarine that exists only inside acomputer. The computer model could then guide construction of thereal vessel. "My dream is to increase the level of detail you cansee on screen infinitely and still continue to display it atinteractive speed," he said. "It may sound impossible, but it'smore possible than it seems."

Kumar's research has been funded by the National ScienceFoundation, the Office of Naval Research and the Department ofDefense.

Related Web Sites:

Johns Hopkins University Department of Computer Science:

Kumar's home page:

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Materials provided by Johns Hopkins University. Note: Content may be edited for style and length.

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Johns Hopkins University. "The Trick Is In The Triangles: Speeding Up 3-D Computer Models." ScienceDaily. ScienceDaily, 25 February 1998. <>.
Johns Hopkins University. (1998, February 25). The Trick Is In The Triangles: Speeding Up 3-D Computer Models. ScienceDaily. Retrieved April 29, 2017 from
Johns Hopkins University. "The Trick Is In The Triangles: Speeding Up 3-D Computer Models." ScienceDaily. (accessed April 29, 2017).