When you want to create an open-world, you have to create tools to ease your workflow first. And as I'm still learning and trying my hands at procedural stuff, I just uploaded a video of a procedural system made with Houdini.
Work in progress of my houdini Digital Asset procedural road and railroad using a curve as Input. Still have to fix properly the UVs and some esthethic parameters. Will probably give the .HIP files once done.
I was working for the past days on a "Rain Parameter" that I could turn on/off to simulate a weather effect. Right now there is no fancy particles but the Collection parameter control rain over the landscape material and a mesh material.
It's based on several tutorials i found on youtube (https://www.youtube.com/watch?v=bXEzhntMnwc), It allows to fill water puddle over a material, with or without rain drops impacts and with a little windy wave effect over the surface. It's not perfect, but will be good enought for now.