Abstract
There are many obstacles in exchanging model data between different CAD systems. One of them is that some CAD systems refuse to supply parametric space curves when sending a model data to other CAD systems. Parametric space curves are omitted because in many cases they are additional information to the real space curves.
Parametric space curves can be essential in many geometric computations such as surface triangulations. Thus a practical issue of computing parametric space curves from real space curves and the base surface is discussed.
The input geometric types are those that are defined in Part 42 of STEP. They are rich enough to cover most geometric types used in CAD systems. For the output geometric types, NURBS form is used since it is the most popular form for representing curves and surfaces.
