Calculation of envelope of curves with C0 continuity
零阶连续曲线包络的计算

The traditional envelope condition that the velocity is perpendicular to the normal is usually used to determine gra-zing points on a family of curves. It only can be used for curves that have C1 continuity at least. If they have Co continuity, thiscondition is useless. In this situation, this paper proposed an extended envelope condition for the curves with C0 continuity.Further, it proved that the extended envelope condition was a sufficient and not necessary condition of traditional envelope con-dition. Based on this conclusion,it presented a new calculation of envelope for deformed non-convex polygon with any shape.Finally, it verified the correctness of this method by using cases.