A constructive approach has been adopted to build interpolatory and freeform cubic spline curves with a more general continuity than /spl beta/-continuity. This method provides not only a large variety of very interesting shape controls like biased, point and interval tensions but, as a special case, also recovers a number of spline methods like /spl nu/-spline of G.M. Nielson (1974), /spl beta/-splines, /spl gamma/-splines of W. Boehm (1995) and weighted /spl nu/-splines. A discussion, for the conversion of complex continuity constraints into simple ones, has also been made for the practical implementation point of view.