Light sourcing
From DoomWiki.org
Light sourcing was a claimed feature of the Doom engine, though it is not actually implemented. The various examples given of the supposed feature
Lamps and lights do not illuminate hallways, and it is up to the map designer to create the illusion it does by playing with sector shapes and light levels. An example of this can be found in MAP04: The Focus where the corridor behind the blue-locked door is split between a "dark" part and a "bright" part.
Explosions do not light up areas, however weapon fire (though the A_Light1 and A_Light2 codepointers) do temporarily increase global light level for the firing player.
Strobe lights remain a purely sector-based effect, and only things inside the sector are affected.
In source ports
Some of the effects associated with light sourcing as described have been implemented in source ports. Most notably, dynamic light seems the closest fit to the description. Lights can be attached to things and to textures; the latter is however less frequently found, with the most notable example being the ray-traced fork of PrBoom+.
The main problem of dynamic lights (or ray tracing) is that it is usually tied only to the object (thing or texture) in the abstract and not to its specific use in the level. As a result, a lamp that is turned off will still emit as much light as much as one that is turned on.
An example of such a scenario can be found in the aforementioned corridor from The Focus. The lamps can be turned on and off, however since they are materialized as textures, if these textures are made emissive they would glow just as much when on and when off.
