A method of deriving an offset profile of a parametric curve includes generating an offset parametric curve corresponding to a received profile of the product represented as a parametric curve based on user input. If no self-intersections in a created spline approximation of the generated offset parametric curve are present, the process is terminated and the offset parametric curve is output as the offset profile of the parametric curve. If self-intersection is present for the spline approximation, the spline curve is split at one or more self-intersections and removed from the spline approximation of the offset parametric curve to form a modified spline approximation. Computing the self-intersections in the modified spline approximation is repeated until no self-intersection is present. The modified spline approximation of the offset parametric curve is then output as the offset profile of the parametric curve.