*.group
About
Source file storing the list of objects in the group.
- Features and limitations are similar to *.level format.
Programs
Blender X-Ray Addon
Blender X-Ray is an addon for the Blender that is designed to import/export 3D models and animations from S.T.A.L.K.E.R. (X-Ray Engine).
IX-Ray SDK
SDK or Software Development Kit helped the developers of the original trilogy and the modders to develop the game itself.