If you insist on 'live view' then AFX, recommended by Puchu, is your option for creating the airport. Like Afcad, it creates the airport and in general it does not place 3D objects.
For 'live view' placement of library objects, like pylons or burning hoops, you have a couple of payware choices. My choice is
Flght 1-Instant Scenery. It has more options and tools than the competitor, Abacus' EZScenery,.... and is a few bucks cheaper.
Both Instant Scenery and AFX are nice programs, are compatible with FS9 and FSX, and can even be run at the same time if your system is capable.
I don't know of any freeware choices that have 'live view'.
Dave
Append:
Quote:or maybe a way to get a section of game terrain to model on it and then resave after?
The freeware
SBuilder has this capability by calibrating an image 'map' to the workspace. It can still be problematic because, when placing objects, you only see an object's footprint. After saving and then viewing the scenery in FS you may find you have to edit an object's heading, scale or other properties.
It's still a good program, particularly for larger projects, as it has all the tools; mesh, terrain, flattens, excludes, object placement and more.
At that time [1909] the chief engineer was almost always the chief test pilot as well. That had the fortunate result of eliminating poor engineering early in aviation. Igor Sikorsky
I intend to live forever....so far, so good. Steven Wright
You know....you can just rip up a to-do list.