月球明亮部分和黑暗部分的分界线。在上下弦时这条线是直线，其他月相时是一段椭圆弧，在新月或满月时和月球的边缘相重合。月面上明暗界线截然分明，是月球上几乎没有大气的一种表现。
明暗界线：月亮或内行星亮和暗的区域之间的分界线。
The dividing line between the bright and shaded regions of the disk of the moon or an inner planet.
轨道正沿着西北方向，几乎和明暗分界线平行，这使得看到一个明显的正北方向的日出成为了可能。
The orbital complex was tracking northeastward, nearly parallel to the terminator, making it possible to observe an apparent "sunrise" located almost due north.
注意中央光和高光的位置是不一样的。明暗交界线是物体从亮部转入暗部的区域。这个就是光线和表面相切。
To test which areas are in light and which are in shadow, you can cast a shadow with a pencil on the object.
应用推荐