In this paper, we study 3D-generalized clothoids, defined as curves for which there exists another distinct curve, with proportional arclength parameter, such that the Darboux lines of both curves at corresponding points are the same. We prove that these curves are those for which the ratio of torsion and curvature τ/κ is a linear rational function of the arclength. We also show that any 3D-generalized clothoid can be constructed from a rectifying curve, which is of constant curvature in the case of a 3D-clothoid.
LUCAS et al. (Tue,) studied this question.