Alright. Before I write anything on the "problem" I am having, I just want to let you know that the aforementioned issue is most likely arising because of my stupidity. However, this could be a bug, so I am making an issue about this anyways. I doubt anyone else is having this problem. Please tell me how I can remedy this.

The problem: I load in a world fine, but after a few seconds, my screen goes white and Minecraft crashes. I have tried this with and without Optifine (since I saw something about shaders), both yield the same result. I have also used ONLY the Weather2 mod and the CoroUtil mod, which are the only mods I have been told are required for the weather mod to function.

Forge Version: 1.12.2-14.23.1.2566 (or whatever the latest version is)
Weather2 Version: 1.12.1-2.6.1 (latest)
CoroUtil Version: 1.12.1-1.2.1 (latest)
OptiFine Version: 1.12.2_HD_U_C7
OS: macOS 10.13.2
Crash report:
crash-2017-12-27_10.21.36-client.txt

If any of these have incorrect versions, just reply the particular mod that has the incorrect version and the correct version (ex: "forge " for an incorrect forge version). If it is otherwise incompatible with something like my OS, please just reply "OS" or "not compatible with Macs". If you need any other info, please say so and I will be happy to supply it to the best of my ability.
Thanks for reading this, and I'm sorry if I've just been stupid and wasted your time.

I noticed someone had the "Error: java.lang.IllegalStateException: Function is not supported" issue as well (although for a different version), and that they complained about not wanting to change graphics cards. If this has something to do with my graphics, please just say so and close this issue.

Ah, good to know. Also...that was the quickest I've seen a mod author reply to an issue. I commend you. Thanks for the reply! I'll be waiting for the fix.

Actually, could I get a full fml-client-latest.log log after the crash happens? My capability checker should have caught that you cant run certain things and prevented this type of crash from happening, this is something i cant reproduce on my machine without the same hardware.

Might have solved it Corosauce/CoroUtil@28986a0

Try out these new builds and let me know if things work or dont, (crash, blank foliage, etc)

coroutil 1.2.2: http://bit.ly/2CdfJXB
weather2 2.6.2: http://bit.ly/2liEw23

Thanks for the report, based on the crash it looks like your mac/hardware cant support my shader stuff, HOWEVER the way I coded it its supposed to gracefully fallback to non shader stuff, this is something I need to fix on my end so your game can still run with old particle renderer and no fancy foliage, will fix soon!

Sure. I'll edit in the fml-client-latest.log for both the old and new versions (new if it crashes or if you want it). Just give me a moment.

fml-client-latest.log (old):
fml-client-latest.log

The hell...same error ("Function not supported")
fml-client-latest.log (new):
fml-client-latest.log

Thank you SO much for your time. If you can't get this to work, don't sweat it. Hopefully I'll be able to build a new PC in a few months.

Thank you very much. You have by far been the most helpful mod author I have encountered on Github, and I hope you keep being the way you are.
I'll let you close this issue as I don't know how long you'd want to leave this up.

EDIT: The world is finally running fine, and I have to say: This mod is awesome.
EDIT: The shaders also seemed to initiate, since I got into the game without touching the configs, unless that has to do with something else.

Nice! Enjoy, and thanks xD. I just happen to be around more to make sure the beta goes well, otherwise I disappear for months at a time ;)

Ah perfect, that log helped a lot, Ok should be fixed now Corosauce/CoroUtil@d2ce362

Unfortunately your computer doesn't support a technology needed for my shaders. but it shouldnt crash now.

Theres also another bug in my code currently that doesnt correctly restore vanilla foliage models if shaders fail to init, so youll have to set forceShadersOff to true in config/CoroUtil.cfg to make it stop messing with the vanilla models. Should have that issue resolved at some point before non beta release.

New build: CoroUtil 1.2.3: http://bit.ly/2Cjgqwn