已知轴线方程,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）。-Axis equations are known, according to the axis of the cylinder divided into several segments, each section in the circle, the circle axis normal to the tangential di