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Ultimate Doom added a fourth sky texture, SKY4, for use in Episode 4, showing orange-tinted clouds with no visible mountains.ĭoom II uses the same names for its three sky textures, but the graphics in the IWAD file are different. The first is a misty gray sky with lumpy greenish mountains, the second is a red overcast sky with brown mountains with light snow, and the third is a much foggier red sky with mountains tinted reddish-black. This is consistent with the backstory, because each episode takes place in a specific venue ( Phobos, Deimos and Hell, respectively), and the nine levels of each episode share the same sky. The original Doom contains three sky textures (SKY1, SKY2 and SKY3), one for each episode.
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The sky is a special effect built into the Doom rendering engine.
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