line of direction, principal

• 主方向线

line of direction, principal的用法和样例：

例句

1. All points along any line perpendicular to the orientation line are the same color.
   与方向线垂直的任何一条线上的所有点为同一颜色。
2. The angle of the orientation line determines which corners the starting and ending lines pass through.
   方向线的角度决定起始线和结束线经过的角。