See "Using Modeling Tools" in the FSX SDK Help:
gmax
In order for gmax to work correctly with the scripts and tools of this SDK, go through the following steps:
1. Ensure that .NET Framework Version 2.0 is installed. If not, install it from:
http://www.microsoft.com/downloads/...CB-4362-4B0D-8EDD-AAB15C5E04F5&displaylang=en
2. Install gmax by visiting
http://www.turbosquid.com/gmax and running the download and installer. After installation you will be required to register with Turbosquid to activate the product.
3. Ensure that the gamepack provided in the SDK (FSX_GmaxGamepack) is copied to the correct folder, which in a default installation would be the C:\Gmax\gamepacks folder.
4. Make sure that you run gmax from the shortcut provided (FSX_GMaxGamePack). The shortcut provides Flight Simulator X specific additions to gmax, and the recommended procedure is to copy the shortcut to your desktop.
5.In order to view all of the features of the Oil Rig Sample file, copy the files from the FSX_GmaxGamePack\textures\DDSFiles directory into the Microsoft Flight Simulator X\Addon Scenery\texture directory.
6. The gamepack supports the tools described in this document (attach point, animation manager, cloud tool, LOD and Guid generation) and FSX Materials.
Note
There is a known issue with gmax that will cause the model textures to not be found on first run of a model. There are two work-arounds to this problem:
. Open the model file once and from then on use the shortcut created at the bottom of the file menu in gmax.
. Redirect the path to the textures directory using Customize -> Configure Paths -> Bitmaps.
.