Using the gradient Tool (g) with a Black to 0% opacity gradient, click and drag a gradient from the bottom up into the planet for the bottom and from the top down for the top of the planet.

使用渐变工具，设置黑色到0%不透明的渐变，从画布底部向上点击拖拉渐变到行星位置，然后，从画布顶部点击拖拉渐变到行星顶端。

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Now in a new layer above the watercolor layer, and drawing straight up, make a Linear Gradient going from black to transparency so that afterwards your canvas basically fades to black down the bottom.

现在在水彩图层之上再新建一个图层，然后从下至上从黑色到透明做线性递减绘制，这样基本上整个画布到底部就褪化为黑色了。

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Click and hold on the Gradient Tool to bring up the Contextual Menu.

点击并保持渐变工具以调出上下文选项单。

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The villages we'd be stopping in would all be 7 to 10 miles apart on a path that follows a steady gradient up a single valley, a positively leisurely prospect compared with the up-and-down slogs from one valley to the next that characterize many Himalayan trails.

WSJ: Trekking the Har Ki Doon Trail in India's Himalayas

For the ultimate show-stopping view, stand at the harbour edge in Tsim Sha Tsui and take in Hong Kong Island's skyscrapers' gradient-defying march up steep jungle slopes.

BBC: The amazing views of Hong Kong

Pushed for time and strapped for cash, the engineers laid eight miles of track straight up Big Hill, at a gradient more than twice the safe maximum.

BBC: The wonders of Canada by rail