vrayenvironmentfog and GI

[Crayox13]

Hi,
I'm using IR and LC to generate it, and it seams that the fog is dimming my GI, as if it's really there lol. I tried making it less thick by increasing fog distance but it's kinda too see through now. Any ideas on how to make the scene more light? Should I just change fog emission from black?

thx

[vlado]

It is kind of a balance thing; you could increase the fog emission a bit, but it may start to look too foggy.

Best regards,
Vlado

[Crayox13]

Yes, it looks too foggy. So how do I fix this? This fog is stopping GI light entering the room, I don't want that. My room now looks as if I'm not using LWF. If I turn the fog off it's ok. So I gather GI really IS stopped by the fog.

[vlado]

You could use a box gizmo to add the fog only around the room. There is also always the solution to calculate the fog separately and composite it.

Best regards,
Vlado

[Crayox13]

How would I composite it? I mean how do I make it render separately and not in render scene? I would have to render it two times or can I render it as an element?

[percydaman]

There is an element for that.

[Crayox13]

Yes, but if I turn on the element, the scene will contain it also, and will be too dark.

What I think is needed (and would speed up the process when you use the fog like this) is to exclude the fog from generating GI. Something like "receive GI" but, "don't generate GI". I would get exactly what I need. Or basically - don't cast shadows

I'm posting the same scene and settings only one has fog active and the other doesn't.

[natty]

Why don't you just have the gizmo where the light is ? you don't need it everywhere do you?

[Crayox13]

But then I'll see the transition. The mist in the air has to be in the whole room.

[natty]

It is kind of a balance thing; you could increase the fog emission a bit, but it may start to look too foggy.

Best regards,
Vlado

Vlado is right, there are lots of ways to overcome this, for instance increasing your ISO, anyhow you dont really see the dust in all the room but only where the light is hitting it?

[Crayox13]

Lol, I'm sure there are. But, what are they?

Playing with emission won't work, even a little increase from black makes the room grey and then white - I want the room light like it is but with this fog.

What's ISO?

[Crayox13]

Oh sorry, you meant vraycam ISO, I rarely use vraycam. Usually just normal cameras.

[Crayox13]

Here is what happens if I increase the ISO. I actually reduced Reinhard burn value to 0.01 so it doesn't burn direct sunlight areas, but it still does. The scene is now barely enough light (in dark areas) so the fog is still just blocking light. How do I stop it???

[vlado]

There is no way to prevent the fog from absorbing light, as this is what it does in the real world also. It might help to set the fog color to pure white though.

And again, there is also compositing

Best regards,
Vlado

[Crayox13]

To composit, I should render the scene without the fog, and then with the fog and a fog as an element, right? There's no other way. I would have to double render. It would be sooo much faster if I could just uncheck "cast shadow" for the fog, or something like that. Which element is now the new vrayenvironmentfog?