in this case the camera is on the floor. Vray perspective correction works differently, in Octane for Max there is no feedback in the viewport.

its only down low (on the floor) to illustrate a point. For what ever image you want, set the camera at the level or position that you want it at. Make ...

here is a low tech fix for the camera wishlist for perspective correction.

set your render pixel ratio to that of a portrait image - something like 1:2 (w:h)
set up your camera as a horizontal camera at the height and position you want it at
render the region you want for you image - verticals will ...