This class represents non-uniform rational B-spline in 3D space.

Autodesk.AutoCAD.Geometry.Entity3d
    Autodesk.AutoCAD.Geometry.Curve3d
        Autodesk.AutoCAD.Geometry.SplineEntity3d
            Autodesk.AutoCAD.Geometry.NurbCurve3d

Public sealed Class NurbCurve3d
Inherits SplineEntity3d

public sealed class NurbCurve3d : SplineEntity3d;