We provide IGES, VDAFS, and STEP translators.

All of our translators run off of a common core, and are very similar in structure. There are three layers in the core:

• 1. Generic utility classes and functions, including a miniature subset of the new C++ standard library.
• 2. The HwNlibObject family of classes to represent geometry and topology, built around the Nlib data structures.
• 3. A set of tools for transfering those data structures into TSLib/SMLib, cleaning up the data in the process. (The cleaning is necessary to handle the inaccurate geometry data that plagues the CAD world.)

For each different file format we support, then there are three available possibilities, each building on the corresponding layer:

• 1. Low level file reading and writing. This layer does not understand geometry at all; it only provides for an internal representation of the CAD file, and I/O capabilities.
• 2. The Nlib layer, which captures all the geometry in the file as HwNlibObject entities. This allows the data to be accessed in simple ways, and converted to NURBS data. While the organizations of trimmed surfaces and solid breps are captured, this provides only a few simple tools for actually working with the data as such. For real trimming tools, you need to go to the next level.
• 3. The TSLib layer, which transports data from the Nlib layer into TSLib using the core's HwNlibObject to TSLib translator classes. In order to handle the inaccurate geometry data that plagues the CAD world, it performs a number of cleaning functions using TSLib's advanced intersection and projection capabilities.

All translators are available as C++ source code, designed with the new ISO C++ standard in mind, but targeted at the prior generation of compilers. Easy-to-use function-based interfaces are provided, as well as the access to the powerful classes used to implement them. The code has been tested extensively on Microsoft Visual C++ and EGCS version of GCC. It has been successfully compiled with Borland C++ 5.01 and numerous Unix compilers.