From Valve Developer Community
Revision as of 12:34, 27 November 2017 by Jackathan (what was that bollocks about brush based light shafts? this entity is obsolete and a dupe of light_spot. not even present in goldsrc)
This is obsolete; its use is discouraged and it may only exist/function in older engine branches.
Leftover from Half-Life 2's early development. Functionally identical to light_spot.
Note:This entity is obsolete and not supported by VRAD! Use light_spot instead.