Creo Elements/Direct Drafting currently supports two types of spline entities: rational cubic splines (C-splines), which are created with the SPLINE function, and B-splines, which are created with the BSPLINE function. Earlier versions of Creo Elements/Direct Drafting only supported C-splines. Parametric Design can be used to parametrically control the shape of any spline, but the procedure for constraining C-splines and the newer B-splines differs somewhat. The following two sections give some tips and techniques for controlling each type of spline.