That scene from one those VN movies, where it’s raining, and the one who has the duty is trying deperately to stay awake, and he’s shaking from being wet and cold, and he’s having problems processing reality he’s so tired, and he’s looking at the terrain and he doesn’t see anything (and you don’t either) and all of a sudden (good thing he wasn’t blinking at that moment) he sees a part of the “terrain” he’s been staring at move (NVA)- that’s the real thing.
Also the real thing: It’s night, it’s raining off and on; one man for every radio is awake, or trying to stay awake; he can’t see two feet in front of his face, but he keeps thinking that he sees and hears something moving out there in the dark. He keeps his rifle trained on a shape than appears to get closer and closer, unwilling to fire and give his position away without being sure of his target, and finally, as the sky begins to lighten in the hours before dawn, he can make out what he has been aiming at all night...a bush!