Volumetric lighting

Volumetric lighting, also known shorthand as "God rays", is a lighting technique meant to simulate light bouncing off fog or dust particles in the air, such as a warehouse or foggy beach. It makes the player see beams of light shining from the sun or other light sources. Currently, the only Valve-made software running on Source that supports Volumetric Lighting is Source Filmmaker, however some third-party engines incorporate volumetric lighting into env_projectedtexture. If the game you are making maps for doesn't support volumetric lighting, you can use some workarounds seen here.

Most versions of Source 2 have support for Volumetric lighting by default

Media

Volumetric lighting in SFM

Todo: alien swarm deferred

Todo: hl alyx

Native Support

Source

Game	Supports
Source 2004 Source 2006 Source 2007 Source 2009/ Source Multiplayer Source 2013 Half-Life: Source Day of Defeat: Source Half-Life 2 Half-Life 2: Episode One Half-Life 2: Episode Two Alien Swarm Alien Swarm: Reactive Drop Half-Life Deathmatch: Source Half-Life 2: Deathmatch Half-Life 2: Lost Coast Counter-Strike: Source Team Fortress 2 Portal Left 4 Dead Left 4 Dead 2 Portal 2	NO
Black Mesa	YES
Alien Swarm Deferred	YES
Source Filmmaker	YES
Strata Source	YES (`env_projectedtexture`)
Apex Legends	N/A