Geometric control of rational cubic curve

Geometrical control of curves is discussed in this paper. The curve representation considered was a rational Bezier like cubic curve. The rational cubic curve is characterized by two end points, two end slopes, a shoulder point and a shoulder line in the case of inflection. A method is introduced in which the convexity and inflecting curve is preserved more intuitively. The paper also shows that the end weights play a significant role in controlling the shape of the curve segment constrained by a shoulder point and a shoulder line.