Heavyweight collaboration through lightweight JT: the ability to visualize design data of various types across platforms is now possible through a file format named "JT." What's more, the file sizes are but a fraction of what's ordinarily been the case. This could be a tremendous boost for those who are looking for more collaborative processes

Automotive Design & Production, March, 2004 by Lawrence S. Gould

One of the things that's been missing in design in general and collaborative design in particular is the ability to sling design data around different CAD, CAM, CAE, PLM, and other applications. Even being able to just visualize that design data without having to buy the CAD application that created those data would be nice. That deficiency has now been addressed: The 3D design world now has access to a file format that makes collaborative design simple, cross-platform visualization a reality, and data integration possible across a slew of applications throughout the supply chain. The file format is JT, which can store directly renderable geometry, analytical geometry, geometric attributes, facet information, lighting models, texture maps, user metadata, hierarchical product structures, and product manufacturing information (PMI), geometric and functional dimension and tolerancing data, and attributes (such as color, layer, and font).

FILE UNDER "LIGHTWEIGHT"

The JT file format came from a small company with a bunch of nifty visualization tools used in a variety of industries. (The company also had some fascinating applications. One was an educational CD for exploring the human body and its internal organs. Another, a 3D animated re-creation of the April 19, 1995, Oklahoma City bombing.) These tools were so intriguing that Unigraphics--now UGS PLM Solutions (Plano, TX)--bought Engineering Animation, Inc. (EAI) in September 2000. With that came EAI's DirectModel (JT) file format. When the two companies merged, UGS took on the lightweight JT file format; EAI added the Parasolid kernel to the tessellated geometry data that JT initially contained.

JT is CAD-neutral; it is a common data format for sharing 3D designs and product visualizations. The format packs a lot of information in a (relatively) small file. JT is specifically for actively exchanging models and product data between applications. It is not a static format, like Adobe PDF, which is a cross-platform publishing standard.

The JT binary file contains four "compartments," each independent of the other. You can populate one and leave the others blank. Explains Chris Kelley, vice president of marketing for UGS PLM Solutions, the first compartment, the initial JT file format, contains tessellated geometry data. This data is basically "surface information in the form of essential points in space and how those points relate to one another. This provides the small--'lightweight'--representation of the geometry." This compartment supports basic viewing and text-based markup. The second piece of the JT structure contains surface geometry. In future versions of JT, this compartment will fully define solid models. This geometry is based on Parasolid, the CAD kernel in all UGS products, as well as in SolidWorks from Dassault Systemes, the CAD applications from Bentley Systems, and other CAD, CAE, and CAM products. The third compartment contains a set of attributes (metadata). "This is wide open," explains Kelley. The compartment lets users pass along a database associated with the part or the geometry. While it's possible to use only that compartment as a text-data transport mechanism, Kelley is not aware of anyone doing that. The last JT file compartment contains PMI. This is a special class of metadata to help companies use the JT files in manufacturing operations, such as creating manufacturing prints, performing inspections, and creating tooling and manufacturing setups using the 3D model itself.

JT files can be 75% to 90% smaller than the source file for CAD geometry. For example, an average CAD file of a simple component--not an assembly--can range from 10 MB to 20 MB; in JT, it'd be a megabyte or so. XML, which is growing by leaps and bounds, is another data transport technology. XML is "open" (maybe too open) and scalable, but XML doesn't have the same "lightweightness"--compression--that JT has.

These characteristics of JT make sharing product data and dynamic images throughout the product lifecycle painless. Even internally, companies are "maintaining JT data as a reference point, as 'master geometry' throughout the product development process and even after as reference to point back to," says Kelley.

MEMBERSHIP HAS ITS PRIVILEGES

In December 2003, JT Open (http://www.JTOpen.com) officially debuted. This forum gives members a "direct and strong voice in the future of both the JT technology and the business model surrounding JT Open," says Kelley. Membership to JT Open is, well, open: end user corporations (such as companies with their own software development group), software vendors, interest groups, and academia all qualify.

Despite JT Open, the JT technology is still the intellectual property (IP) of UGS PLM Solutions, explains Kelley. "We're not giving up any ownership rights to that, per se, as a result of [JT Open]. We're not throwing it out onto the market. Nor are we turning over the IP rights of the JT format to an independent or an outside organization. It's copyrighted in the U.S.; we have patent protection on it." This is not a new strategy for UGS. The company took basically the same approach with Parasolid, licensing it and essentially creating a de facto standard on the Parasolid side for a precise geometry model. In fact, points out Kelley, UGS licenses Parasolid to its "fiercest competitors" and has no intention of revoking those licenses.