A tool path generating device (20) which generates a tool path (L1) for machining a hairline-shaped long narrow groove (Wa) of on a workpiece surface (W0), includes a shape data acquisition part which acquires shape data of a workpiece, a parameter setting part (23) which sets a shape parameter of a hairline corresponding to the long narrow groove (Wa), and a path generating part (24) which generates a tool path (L1) for a hairline machining, based on the shape data acquired by the data acquisition part and the shape parameter set by the parameter setting part (23).

Methods of fly-cutting a workpiece are disclosed, and in methods in which the position of a fly-cutting head or its associated cutting element is known as a function of time. Also disclosed are methods of forming features, such as grooves or groove segments, in a workpiece such as a cylindrical roll. The features may be provided according to one or more disclosed patterns. Articles made using tools machined in the manner described are also provided, such as polymeric film or sheeting that exhibit certain beneficial properties.