在被称为曙暮辉的太阳光线的照射下，它们实际上是由靠近遥远的西方地平线的云层产生的阴影，此时落日在云层的正后方渐渐隐去。
Outlined by rays of sunlight known as crepuscular rays, they are actually shadows cast by clouds near the distant western horizon, the setting sun having disappeared from direct view behind them.
麦凯是在BBC的一个录音室里第一次看到这个效果的：那位正在播音的职员被平行线柱上线条空白间上下跳动的阴影错觉搞得很不耐烦。
MacKay first observed this effect on the wallboard of a BBC studio: the broadcasting staff had been annoyed by illusory shadows running up and down blank strips between columns of parallel lines.
有几个专门用于线性图表的折线图选项，如标记(显示数据点)、张力(使直线弯曲)和阴影(给每条线一个下拉阴影)。
There are a few line chart options that are specific to a linear chart, like markers (show data points), tension (make the lines curvy), and shadows (give each line a drop-shadow).
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