Cast light on volumetric clouds

Development Rendering
1

Hey there! Am currently experimenting with volumetrics.

Can lights somehow affect volumetric clouds like they can do with volumetric fog? I’d like to achieve something that looks like a thunderstorm storm, as can be seen in this video:

But while fog gets brighter through spotlights for example, I somehow cannot get it to work for clouds. I tried placing a large points light inside the clouds or a spot light that beams directly through them, to no avail. According to this twitter thread, if I understand correctly, the lightning effect is achieved (faked) through the cloud material:

2

Volumetric clouds can receive light from directional lights (though I think they have to specifically be flagged as an atmospheric light)

Afaik for anything else you need to use the emissive output of the material.

3

betting they used distance-fields from the lighting mesh/string thing and made the emissive sensitive to that.

4

Yeah, they showed that in the volumetrics / sun light demos, but you mean they cannot be affected by other light sources?

So everything else has to be “faked” through the emissive of the cloud material?

For lightnings or anything else that is “inside” the clouds, I see no problem there. But how’d you do something like airplane searchlights? Anything like far range spotlights basically… just curious

5

I would not describe it as fake but yes you need to do it in the material.

Same way you’d do lightning. Define the volume of the light cone and use the clouds emissive output. The only thing you can’t really do easily is shadow casting.

For what it’s worth, someone has already put together a system for automating this on the UE marketplace: Clouds Lighting System in Code Plugins - UE Marketplace

6

Alright, thanks for the intel!

The asset actually looks interesting, thank you for taking the time to look it up.