Curve entities can be divided into "specialized" curves (lines, circular arcs, ellipses) and NURBS (Non Uniform Rational B-Splines). The latter describe the remaining types of conics and all other types of curves (helixes, splines, etc.) supported by think3 applications.
Each curve, irrespective of its type, has a parametric representation, that is to say, it is expressed by a parametric equation with degree n as a function of parameter u which varies within the range [0,1].