This resourcepack adds cool fog to your Minecraft world! It uses core shaders, something added in 1.17, so it's a little bit experimental. But I thought it looked cool and maybe other people would like it, so here it is for download. Make sure to set your graphics to Fabulous so the shader can take effect.
You can adjust the fog level by editing the "fogginess" variable in shaders/program/fog_depth.fsh.
Shader is loosely based on the depth_test shader by onnowhere. It's probably not compatible with Optifine shaders.