Very dumb Arctic fox. Giving out free and open-source hugs. Also a GoldSRC modder, and a gamedev. (idTech 3, 4, Unity, Unigine)
Vanilla HL can only go up to 8192x8192 units.
But, it seems that mods can change this easily. I first tried going up to 16384x16384, then 32768x32768.
This map, however, is 57344x57344 units. Close enough to 65k anyway. :D
Oh! So open-world in Half-Life is possible now? Good job there dude
Hell yes! >:D
Gotta fight the other limits tho'.
Clipnodes (collision data) and AllocBlock/lightmaps (lighting data), mostly. Those quite simply cannot be lifted without engine access, and my goal is to do stuff without engine access, so.
This map in the video currently uses 20% clipnodes and 10% AllocBlock, other limits are mostly below 5%.
With a more optimised design, or with a different approach, I think we could well make maps within limits that are open-world at the same time. So yeah.