Hey, I made this for Codrops, like 2 or 3 years ago?
I mean, the rain effect itself, not the whole UI around it here.
Edit: Here's[1] the accompanying article, and here's[2] some other stuff I made (although my website is also just as old and hasn't been updated since!)
I don't know why this isn't getting more attention/comment (someone else independently posted it looked similar below with another link to your domain) but here's the one I found from your profile link for comparison http://tympanus.net/Development/RainEffect/
Welp. It's identical. I even tried to defend the current link with "Well, some cool things can happen when you hook up a UI to a shader..." but the UI doesn't even do anything except turn the rain off and on.
There's lightning too in that other one! That's so cool.
What’s some good reading for a basic and well-explained entry into GL and shaders. I feel like so many tuts gloss over really important stuff. I’ve never written a shader.
As an aside, I’m sorry someone stole this from you and used it unattributed.
You've probably come across it though, as it does seem to gloss over some basic stuff. But it does cover the basics pretty well, just gotta keep an eye for details and seemingly unimportant one-liners that turn out to be fundamental.
It also takes some googling for deeper explanation of some functions, which often result on Stack Overflow answers by the author himself.
Dealing with the WebGL API itself is a bit... let's say tricky, though. But working with shaders for me is a joy.