Taken from the Battlefield2 official site
Gmax Tools Released
I’d like to announce that we are releasing the first version of the Gmax plug-ins to be used in conjunction with the Battlefield 2 Editor. These tools provide the same basic functionality as those provided for 3D Max. That being said, please be aware that because of the limitations of Gmax itself, there may be some differences.
For instance: the game requires textures to be in the “.dds” format, but Gmax does not support this. The workaround is to use a supported format, such as “.TGA” while working in Gmax and then swap out the textures at the end.
In order to alleviate any difficulties you may have, we have set up a Gmax section on our modding website. We invite anyone to post questions there once the tools are released. We will be monitoring things there so that we can deal with any potential issues as quickly as possible. You can find the forums at http://bfeditor.gotfrag.com/forums/
Good luck, and happy modding,
-Battlefield Mod Support Coordinator