Sampling and lighting differnces in vray 3.4 vs 3.3 even after uninstall

[japetus]

I'm having some problems with consistency between vray 3.3005 and 3.4 for Max 2016. The sampling and the direct lighting on some fine and white (255,255,255) objects is different, causing flashing in animation. I've since downgraded those machines back to 3.3 and the sampling is the same again, but the lighting on the objects is still different (white vs grayish). It wasn't occurring at all before vray was updated (wasn't my choice to do it). I've checked the the Max folders when I uninstall and all the files seem to be gone,but it's really frustrating me that I can't get it back to rendering how it was before! Is there some new file in vray 3.4 that doesn't get uninstalled, or some setting that carries over? Here are a couple image comparisons, you'll notice the lack of brightness in the tree in the second image.

Edit: I would also say, the material is pure white diffuse w/ white reflection filter, default fresnel, raytraced reflection is disabled and it's using GGX. My guess is maybe GGX has been changed? About to test it...

[White Wizard]

It's not recommended to use values of pure white or pure reflectivity in vraymaterials. The reasoning is that Vray is based on real world lighting principles and pure white and 100% specularity don't exist in nature. At least that's the way it was once explained to me. Setting these values to maximum can cause glitches such as what you're describing.

I would recommend lowering your values from 255 down to something like 245 or 250 and seeing if you still have this problem.

They did update the GGX shader recently as well because it was causing fireflies.

If lowering the values doesn't work, you can also try adjusting Max Ray Intens in the Global rollout to a lower number.

[japetus]

Yeah, I know about the 255 thing, I'm rendering a snowy world at night, so need all the light I can get. It still doesn't explain why, after uninstalling and reverting, the render is different than it was before and it never had this issue in the past. Will keep exploring I suppose.

[Morne]

Not sure why uninstalling and reverting isn't working.
However, I would suggest to find a way to make it work with 3.4.
Snowy world at night is no excuse to use 255,255,255. Besides laws of nature, it also makes the work of your lightcache harder. Granted this is at night.

I would suggest to use usual white (beteen 170,170,170 and 190,190,190) and light your scene properly. It can be a moonlit night, or even nice starry night or whatever. Even if your shot calls for a blizzard at midnight, it's never pitch black outside. Either add some fill lights, or use a directional light as moonlight. I'm sure you can make it work

DOUBLE CHECK that all machines are running the same version of V-Ray. It's sounds pretty trivial, but these things happen.

Those branches look on the thin side pixel wise, so make sure you use proper AA and you can also try rendering with smaller buckets

[japetus]

It's kind of too late to do it at this point since I've already rendered 4000 frames correctly w/o this problem. 3.4 was only installed on 3 out of 15 machines and now those are the machines that are doing this. There is actually a dark blue sky, just the background is being overridden. I'll try AA sampling but don't think it'll help. I can see the problem occuring in the direct lighting pass, but all other passes seem fine to me, even aliasing wise. I can reliably duplicate the problem by rendering on those machines and get rid of it by NOT using those machines. So it's something that 3.4 did somehow. Unfortunately they are the fastest render nodes.

Edit: and actually there are some shadowing and loss of detail in areas of bump maps on those same frames too...very odd in deed.

[japetus]

Well, much to my chagrin, i tracked down the change as far as I can tell to a change in 3.00.3 vs 3.00.5! I assumed they were running 3.3005 when in fact it was 3.3003. Soo...if this works I guess I'll just fade between the two versions. Thanks for the tips anyways guys.

[Zdravko.Keremidchiev]

It is very important to maintain the same V-Ray version across all of the nodes in the pool in order to preserve the same result and quality. Especially with the latest releases where a lot of changes and new features were introduced.