FBX
FBX (Filmbox) is a proprietary model file format developed by Kaydara and owned by Autodesk since 2006. Although the format is proprietary and not officially documented publicly, it has been thoroughly reverse-engineered, and as such proves a popular format for intermediate transportation between applications. Many modern modeling programs, such as 
Blender, support FBX natively.
The StudioMDL used by the 
CS:GO engine branch version of 
Source 1 supports FBX as an input format for static meshes. 
Source 2's 
Hammer 5.x and 
ModelDoc Editor support importing and exporting models as FBX files as an alternative to using DMX files.
See also
External links
FBX on Wikipedia
