Vray EnvironmentFog - behave like Corona fog, is it possible?

[Jiri.Matys]

Hi,

in Corona when I use a box as a fog and select one light to influence this fog (nothing else) fog is visible only in this light and evewhere else is transparent and doesnt affect the scene at all.
But in VRay when I do the same, one light affect the fog like make it brighter and everywhere else the fog just darkening the scene so it is visible.
I really like the way how corona make it in this case. Can you make it?

Thank you.

[Jiri.Matys]

Anyone from Chaos please?

[dimitar_panayotov]

Hi, can you give an example? We will need more details on how the fog is set up in Corona. Maybe some images of the end result.

[Jiri.Matys]

This is it.
I have a box as an EnvironmentFog gizmo. And one light selected as the only source to affect fog. And this is the result. Light affect the fog BUT the fog is visible everywhere darkening the rest of the scene.
Corona on the other hand show fog only where light source really lighting the fog. And the rest is transparent. Which makes it much more usefull in a lot of situations.
It would be really great if you can make this type of behaviour in VRay. Is it possible please?

[Jiri.Matys]

It was in MasterClass series from Nikos Nikolopoulos. I dont remember the exact steps in Corona. But he show this in night beach scene for car lights.

[seandunderdale]

Ive often wondered this. Where you want the fog only visible in areas where the light interacts with it, and not clouding the scene in general. I still assume its a settings issue on my parts. Perhaps it just needs very thin vray fog, and very intense light sources?

[Jiri.Matys]

Ive often wondered this. Where you want the fog only visible in areas where the light interacts with it, and not clouding the scene in general. I still assume its a settings issue on my parts. Perhaps it just needs very thin vray fog, and very intense light sources?

No, this feature is just missing in VRay.

[dlparisi]

It's not really a solution because the fog is actually still visible everywhere (or within the gizmo), but you can increase the fog distance a lot (like a factor is 10 or more) and increase the "affect atmospheric" spinner on the lights by a corresponding amount. Not perfect but it may work for you.

[seandunderdale]

yeh this is kind of what I was getting at. A very very subtle fog overall, so its imperceivable, until you bang an intense light at it...and the suggestion of cranking the affect atmos is better since it doesnt affect the rest of the lighting. For sure it sounds like a workaround rather than how youd want it to work.

[Jiri.Matys]

We need an option to behave like in corona, thats it. Please can you add this feature Chaos?

[dimitar_panayotov]

I will check with the devs to see what is possible.

[Jiri.Matys]

Great, thank you a lot!

[Joelaff]

Would this basically be an additive only mode? The fog could never darken, but only lighten? Or does it work differently somehow?

We often end up doing this as a pass (often with an empty VRayVolumeGrid) and comping. But I am all for more doable in the renderer.

[Jiri.Matys]

Anything new on this please?

[dimitar_panayotov]

Hi, I discussed this with devs and other teammates on both sides. There aren't any big differences between Corona fog and V-Ray fog. By default, Corona has Scatter GI On, while V-Ray has it Off.
If you want to achieve the result you want with V-Ray, you can turn on the Scatter GI, set the fog to something almost transparent, and increase the "Affect Atmospherics" value in VRayLight.