Is there a way to exclude a light from vrayenvironment fog?

[evanerichards]

So I have a rectangle light that I want to cast a beam in the scene. But I have a dome light I want to give some ambient light to the scene. The fog darkens and diffuses the dome light too much though. Is there any way to have all the lights act normally except for the specific ones I want to be creating the beams of light in the environment fog?

Please advise.
Thanks!

[yolov]

It could work if the fog is in a mesh container (mesh with a fully transparent material, envFog as volume shader to the material's shading group). Then you could just break the light (+shadow) links between a specific light and the mesh.

[evanerichards]

I've never used a mesh container that I know of, but I'll look into this method and see if I can figure it out.

Thanks!

[yolov]

You can wrap your whole scene in one big cube, assign a fully transparent material to it and put the fog in the shading group (as opposed to the fog being an environment volume). That's pretty much the whole setup, but it will allow you to play with the light linking. I hope that works

[evanerichards]

Ohhh. That sounds like a really good solution for controlling vray fog to begin with. I'll definitely give it a shot.
Thanks!

[evanerichards]

Ok, apologies but I'm having a hard time making this work.

I took a cube, scaled it up so my entire scene is contained inside it.
Added a vray material to the cube. Set that material transparency to 100% then I took a vrayenvironmentfog and added it to the shading groups "volume material" slot.

This does not seem to work though. Even if I dial the density of the fog up to full and distance down to .1, and the height up to 10000 I still see nothing. No light beams so fogginess, nothing.

What am I doing wrong? What you said to do seems easy enough, it just doesn't seem to be working. Can I not use the vrayenvironmentfog in the "volume material" slot?
Thanks!

Update: Ok. When I render the volume cube by itself the fog DOES seem to be working. The lights just don't seem to be creating beams in it the way they were when the vrayenvironmentfog is applied to the "environment volume" slot in overrides.
Update 2: After some experimenting I find that the light IS creating a beam in the volumetric fog but as soon as the camera goes inside the fog volume the beam immediately disappears. Is this expected behavior?

[vlado]

I will post a set up for you later today.

Best regards
Vlado

[evanerichards]

That would be great. I'll look forward to it.

[ralenekov]

Please take a look at the example. The camera is inside the gizmo.
The setup is like this: A box gizmo with added material with zero opacity. Created EnvironmentFog node and added the gizmo to the fog node's set. Then the fog is added as an environment volume.

[evanerichards]

I understand now. See, as I mentioned in my previous post, I was taking the vrayenvironmentfog and applying it to the "Volume material" slot of the 100% transparent vray material. But it looks like that's not how you applied it. You applied the cube itself to the vrayenvironmentfog group. I didn't know you could do that.
Thanks so much for sharing that setup! I really appreciate you taking the time to do that.

A very useful trick to know.

Cheers

[yolov]

Hope it works for you case. Both ways are perfectly fine to use, only the one that Ivan shared uses the cube as a "gizmo" for the fog, meaning the fog height will be constant.

[evanerichards]

Hope it works for you case. Both ways are perfectly fine to use, only the one that Ivan shared uses the cube as a "gizmo" for the fog, meaning the fog height will be constant.

So does this mean that when you apply the vrayenvironment fog to a geometry that the fog just fills the volume and the fog level doesn't do anything?

[yolov]

Only the fog height is ignored.

[evanerichards]

Understood. That makes sense.
Thanks!

[evanerichards]

Only the fog height is ignored.

Is it possible that excluding the environmentfog box from the light using light linking doesn't have any effect? I just tried this and the renders are identical. Hmmmm...

*edit* - I swear it wasn't working yesterday with this one light I was working with. But today it seems to be working although with a different light.