Rendering Line Drawings of Curved Surfaces

Freeform surfaces are very common in the design and modeling of objects, especially when modeling complex objects with curved surfaces. The advantage of working with freeform surfaces is the ability to control the shape of a surface with control points so that the location of the control point influences a well defined part of the curved surface. The greater the complexity of the curve, the greater the number of control points. For a deeper insight into the mathematical matter of freeform surfaces we refer to [Far91, Sei93].