用MATLAB画一个弯曲的圆柱

思想：把圆柱按轴线分若干段，在每个断面画圆，圆的法线就轴线的切向方向。柱面画若干平行于轴线的线条，其中用到平行单位矢量点积等于1，不平行的结果是[-1，1）。

-MATLAB painting with a cylindrical curved thinking: the cylinder axis by a number of sub-paragraph in each section drawcircle, round on the normal axis of the tangential direction. Painted a number of cylindrical axis parallel to the lines, which use a parallel unit vector point plot equal to 1, the result is not parallel to [-1,1).