Freeform surface

Surfaces, different from the canonic ones (plane, sphere, cylinder, cone), generated by extending the profile along a 3D curve, building a spline surface according to the control points, smooth connection between two patches, etc. Such surfaces play an important role in the aircraft and automobile industries. In particular, the so-called A-surfaces are formed with highly smoothed patches in the connection points (requiring matching not only osculating planes but also curvature).