Hmmm the title little misleading, this is a RT mod for Half Life 1 so in a similar vein to Ray Traced OG Doom or Quake / Quake 2.
This is *not* a ray tracing mod for the Black Mesa "fan remake" that launched within the last few years that was built on the Source 2 engine.
Source 2 is such a light engine by modern standards that it would be interesting to see a Half Life 2 "RTX" someday.
I think the lack of pre-baked lighting in the turn of the century titles actually makes it easier to drop in RT effects through, since any RT in games from 2010 onward would have to account for pre-baked light/shadow maps and such.