Curves
Curves used in BRep geometry are defined as smooth mapping of a range of its parameters to 3D or 2D space. The range is part of curve definition
Common properties of a 3D curve are accessed via ICurve_DG interface. Normally a curve has a specific type like BSpline curve accessed via IBSplineCurve_DG.
2D curves can be accessed via ICurve2d_DG.
Curves on a 3D surface are normally defined as a mapping of a curve in two dimensional plane of u,v parameters of the surface to 3D.
Such 2D curves are called Pcurves
