BRep Geometry
BRep Geometry is the internal set of equations and related data, which describes the underlying smooth surface
for faces and smooth curves for edges
BRep Geometry for faces can be accessed via IUVSurface_DG obtained with
IBRepFace_DG.GetSurface().
BRep Geometry for edges can be accessed via ICurve_DG obtained with
IBRepEdge_DG.GetCurve()
Parameters
Depending on dimension, points of BRep Geometry are accessed using two parameters (u and v are the normally used names) for
surfaces or a single parameter for curves
Range of each parameter is part of definition of the specific geometry
BRep Geometry can be thought of as a mapping of one or two dimensional range of parameter space into 3D space
BRep Curves
Parameter range for curves can be accessed via ICurve_DG.GetParameterRange()
A curve is closed if its ends coincide
BRep Surfaces
BRep Surface can be thought of as a mapping of a rectangle in u,v plane into 3D space. Quite often the equations allow
extending of definition of the surface outside of the rectangle.
See more at BRep Surfaces
