In S. N. Goyenka Vipassana meditation you have to scan your body from head to foot and foot to head. Now I take my attention or [ध्यान dhyaan] at top point of my head, so it’s a 2d point now I move from this point in 2d on surface of my body and I can either go from my front side or from back toward my foot. I'm not getting how to scan my body in 3d? And if I scan in 2d its take too much time to scan whole body if I go inch by inch. People working in this mediation may get my point what I’m trying to ask.
With sufficient practice one can develop the ability to very quickly and accurately observe several points in the body in very quick succession.
In a single mind moment only one point in the body is observed, however since mind moments are so fleetingly small, with good concentration intermediate meditators can pass attention to several points in quick succession such that it can appear as a single observation.
With good concentration one can pass the attention from top-down in a ray trace fashion, or left-right, and observe all points in between.
There is no reason to be in a hurry, or be impatient - the quality of meditation does not depend on the number of times the body scanned, but on the quality of the observation. If it takes a lot of time to go inch by inch, that is valuable practice too, since it develops patience and perseverance.