Rectangular objects do their own thing in space. Not only are they affected by eye level (above, at, or below), but they also change as you see them from an angle other than straight on. As you see a rectangle from an angle, the face or plane that is slanting away from you starts to diminish or vanish. So a plane in space needs to reflect that vanishing as well as its place relative to eye level.
Note how this cube in space starts to diminish or vanish.
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