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 direction. Number of cylinders parallel to the axis of drawing lines, which use the parallel unit vector dot product is equal to 1, the result is not parallel to [-1,1).