C~3 continuous Bézier spline curve with given tangent polygon

Proposed in the paper is an approach of constructing planar piecewise Bezier curve of 6th degree with all edges tangent to a given control polygon and the curve segments are joined together with C~3-continuity. The segmented Bezier curves are all shape-preserving to their tangent polygon. The admissible scope of the inner control points of the adjacent two curves is given in order to guarantee C~3 continuity at the common joining end. Local modifications for these curves are possible,and the tangent polygon can be approximated locally or globally. Finally, a few numerical examples illustrate that the method given in this paper is effective for CAGD.