Last week, forumite michi.be over at the MapCore chatboards raised questions about certain DOOM 3 / Half-Life 2 assets being used in GSC Game World's action/RPG S.T.A.L.K.E.R. As it turns out, those particular assets are indeed being used by both titles, but are part of a package sold by Marlin Studios, which lists both Valve and Activision as its customers, and confirmed its pre-made textures are being used in Half-Life 2.