How Rain Works in Video Games

You can find very specific accounts on X/Twitter, like Can You Pet the Dog? so it's not a surprise there is a person (or people) whose aim is "chronicling good rain in video games." Video Game Rain has over 13,000 followers, so I'd say players and developers are interested in how rain looks and functions in games. So today we're going to develop this topic, see some great examples of well-made rain, and learn how it's created.

If you read 80 Level often, you might remember that we talked about rain in Starfield not so long ago. In the game, there seems to be a cloud "stuck" above your character, and if you scroll far enough in the photo mode, you can see where the rain ends.

This is an interesting decision as developers usually attach the effect to the camera so you see it all the time but the computer doesn't have to render every droplet, only the ones in front of the camera. This, of course, affects performance positively.

As Iron Lung's creator David Szymanski mentioned, rain is usually made with a particle system. Each droplet is a particle, which reaches the bottom of the screen and then goes back up once it's out of your sight. 

Some developers go to great lengths to achieve a convincing rain effect. PC Gamer has a great article about this. There, Fireblade Software's VFX artist Aaron Miller talks about making the raging rainfall in its roguelike Abandon Ship:

Particles dropping from above might not be enough to create believable rain, so make sure there's some splashing when they hit the ground. Just look at this evolution of rain compiled by GamesRadar+ and learn from famous devs.

There are plenty of nice tutorials on how to make rain, and here are some of them.

Unreal Engine has a VFX called Niagara, and this is probably your best shot if you want some rain in your game. In the tutorial above, Matt Aspland goes over the process of setting up the right effect and adding collision. It's for UE4 but I still think the video is useful to learn the basics of what to do with this type of weather.

Zihe X also has a detailed tutorial on rain, explaining everything from creating drops to working with channels and altering textures to then making ripples.

Here are some other guides you might find interesting:

But just helping particles fall from the sky is usually not enough to create great rain that will make history. Engine programmer Amandine Coget pointed out some things to think about.

Consider reflections – an important part that often helps you understand if a game has good graphics or not. If you want to learn how reflections are created in video games, check out this article. Rain makes reflective surfaces, and your puddles need to be glossy enough to fool the eye into thinking they're real. Just don't overdo it.

When it rains, the sky darkens most of the time, so you need to reduce light. Thankfully, nowadays you don't need to change textures for each weather effect, but imagine what developers went through back in the day!

Coget also mentions the importance of coding: "Whether it’s raindrops, rain sheets, or splashes, VFX and particle systems require coding assistance. Code to calculate where the ground is so splashes are properly generated, layer raindrop effects in order, and so on."

Finally, the world needs to change together with the weather but not too suddenly. Puddles, clothes, and hair take time to dry and go through different stages of wetness. This field is still undergoing research, and maybe one day, great minds will create a system that can handle such changes automatically.

I hope this article helped you understand how rain works a little better. Naturally, every engine has its own nuances when it comes to development, but this is an overview of the process.

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