notes-computer-3dInterfaces

one useful thing about 3-d is that there are various network diagrams (specifically, non-planar graphs) that cannot be drawn in 2-D without (spurious) intersections:

https://people.hofstra.edu/geotrans/eng/methods/planarnonplanar.html

in 3-d you can draw these without edge intersections by going over or under something that would be an intersection in 2-D.

e.g. when driving, where the roads are 2-D you have to have intersections and so you have to have stoplights, which are inefficient. But when you can afford to build roads in 3-D you have overpasses and underpasses, which is why you can have highways without stoplights.

i think this is very important because it is a qualitative, not merely quantitative way in which 3-D (and higher dimension) differs from 2-D.