Hello !
I am having an issue with the latest builds of vray (3.3 and 3.4). When using maps (noise or bitmap) within the environnement fog maps slots the fog goes crazy (values go up to 300+).
Here is examples.
No maps :
Noise in any slot :
I tried lowering the values black and white in the maps, having black at 0 and white at 1 (255 8bit scale) and it doesn’t really fix it.
Is anyone having the same issues ? This mean I can’t breakup the density of the fog which make for very flat images 
Have you tried using levels/exposure in 32 bit exr/half/full range? You should be able to adjust the range to more comfortable spot… ?
Its something you should do in post… But maybe there is issue somewhere else.
It does the same thing in post
…
Click on alpha channel
Click M
Click CTRL + A > CTRL + C
Make new paint layer(not in channel)
CTRL > V
Create Exposure/levels above that.
Adjust the values
Select both
Merge
M>CTRL A> CTRL C>
Paste in Alpha channel 2 for example
Use alpha 2.
Maybe invert texture as well ? Not sure… The issue could be scene set up > render set up> vray bug>user error…
More or less…
Still doesn’t work. The main issue is that fog values go crazy high when pluggin a map into emission. I have the same issue at work and at home, so on 3.3 and 3.4. Using simple scenes
I don’t know
Can anyone try this : create a boxgizmo with vrayfog, have bright fogcolor and a dark fogemission value and then plug any map (noise, bitmap, …) in the emission slot and see if it breaks the render ?
Also since the fog goes very bright I tried lowering the white values of my noise (with output like 0 for black and 0.0001 for white) and it does expose the fog more correctly but i lose all the shading on my objects, everything is black.
Mmmm ok can you post a test scene?
Why use fog emission to break up your density?
You need to put the map in your density slot. Also your step size needs to be about half or 1/3rd of your fog distance.
http://www.the-boundary.com/blog/2015/5/2/carey-house-tutorial-08-atmosphere
edit:
Just tested it and works as it should here. (I think) I didn’t use a gizmo (although tested, it works just the same)
It works for me also when having emission all black. But try doing the same image with some color in the emission slot, it breaks.
I am working on a project with a very foggy scene (like you can’t see past 15meters) so I need to have emission otherwise all the lighting gets absorbed by the density.
Have you tried to disable affect shadows and affect GI?
We’ve reported the issue as a bug and will post in this thread when we have any updates.
I do have the same issue, I have to use volume grids with simulation.
