NurbsSurfaceData.ReverseOrientation Property

If true, the surface's orientation is opposite to the canonical parametric orientation, otherwise it is the same. The canonical parametric orientation is a counter-clockwise sense of rotation in the uv-parameter plane. Extrinsically, the oriented normal vector for the canonical parametric orientation points in the direction of the cross product dS/du x dS/dv, which S(u, v) is the parameterized surface.

public bool ReverseOrientation { get; }