Older versions of Vray into 3.6?

[SonyBoy]

I'm noticing that when I render scenes set up with older versions of Vray, it's necessary to use local subdivs to get noise-free results, no matter the settings. Is this expected behavior?

[Muhammed_Hamed]

I don't think so. The default settings should give you cleaner/faster results in most cases.
Check the min shading rate if it is set to something like 1 or so
Does this happen with all your scenes?

[SonyBoy]

Min and max was originally set to 1 and 36. Tried bumping up max samples as high as 64, lowering threshold to 0.008, changing GI settings and a whole bunch of other stuff. Nothing would clean up the noise, except turning on Use Local Subdivs. It's a pretty old scene, probably Vray 3.1 or 3.2.

[Muhammed_Hamed]

Sample rate and GI render elements will show the reason behind this noise. Can you share them here?
Not having enough portals with interior scenes will cause noise, low resolution HDRIs or light textures, wrong IR or LC, bad global dmc sampler settings...etc
Make sure you reset everything to defaults, then use these settings,
Set min subdivs to 1
max subdivs to 32
noise threshold to .008
min shading rate to 16
GI to BF + LC default settings
Dynamic memory limit to 0
Use local subdivs should be off

[SonyBoy]

I think the only setting there that I didn't already have is the min shading samples, which was probably 6 or 8 and is usually plenty high enough for other, similar scenes. It's clearly a sampling issue as the noise appears across multiple channels (not just in GI, so it's not GI flickering). HDRI resolution is plenty high enough -- 5k. I can't share the scenes, unfortunately. I will check that the DMC defaults didn't get futzed with as well though.

[SonyBoy]

Just reporting back on this -- DMC settings were all at defaults, but bumping up the min shading samples to 16 as you suggested seems to have done the trick. I've never set this above about 8 before so didn't think to look at this. Seems strange that it needs to be so high compared with other scenes... could that be something to do with shading algorithms from older shaders? I don't know what gets carried across to newer versions of Vray. Anyhoo, problem solved. Thanks for the help.

[yolov]

Can you check what gets returned with this MEL line:

getAttr vraySettings.dmcAdaptiveMethod;

If it returns 0, try setting it to 1, disable the local subds and see if that helps:

setAttr vraySettings.dmcAdaptiveMethod 1;