The actual fact of the matter is that not all parallel lines seem to converge AT the vanishing point of a person, they would only converge along the midpoint of the projected line in the middle of these two parallel lines! If someone was standing in the middle of a flat piece of desert, and in the middle of parallel lines were stretched out in front of him at widths apart of one inch, one foot, one yard, 100 yards, 1000 yards, 5000 yards, 3 miles, and some further outside his vision, the first 3 would appear to touch well within his vanishing point, the 4th maybe near the VP, while the others would only appear to be converging inwards to meet way beyond the VP or will not even be visible yet. Add two parallel lines 32 miles high, but 6000 miles apart, visible just above the horizon (ie the size the sun appears to be) and these lines will not even seem to converge at all, apart from the fact that they would start to look much smaller than the sun as they recede into the distance. In fact if you could still see these lines 9000 miles in front of you and they ended, there would still be an angle of over 40 degrees between them. Now turn this point of view through 90 degrees an imagine it in the vertical plane. The same would apply.