Project RDX is a mod based on the IDTech3 engine. The goal is to make the game more complex, and balanced between the "ol' school" and "realistic" games.
Stub of weather effect (in a new map). I've updated the particles to be up to 32678 (instead of the vanilla 1024); a density of 10.000 (generated around the player) is enough to make a rather thick rain (much more so than on the screenie).
Something's still to be fixed (rain going through solids, and deformation when looking the rain straight up), but this is a fair start.
(also, you can notice a (real-time) clock on the lower left. It can be toggled on or off via cvar, and will be included in the next release).