3.2 Very long frames on Hair with Motionblur

[Moriah]

We're rendering a scene with an environment and a character that uses hairfarm for its feathers, motion blur is on and light cache settings have leak prevention at 0.8 and the adviced lc settings to avoid flickering. There's no flickering but on some machines the light cache gets REALLY slow, and when its done the render is also really slow. Usually the LC takes 30s to calculate but on those machines it takes 10min. Then on the render itself it usually takes around 10-15min and on the bugged ones it takes around 10-14h.
When i turn motion blur off it renders fine as far as i've tested, the thing is we need motion blur for this character.
Also the most of the feathers were turned to poly planes, and we used opacity maps to speed the process, and i'm using stochastic on those materials (probably 15 of them). Don't know if it's anything to do with it, but from what i've seen its something with hair and motion blur

Any advice?
Thank you

[vlado]

It would be best to get us a scene for debugging to support@chaosgroup.com or to me at vlado@chaosgroup.com

Best regards,
Vlado

[Moriah]

Just sent it to you. I sent other test renders with a material override and the same happens. So its nothing to do with opacity maps/stochastic. Also it gets stuck on the same frames. 5,28,29,31,35,40,42,46,49,53 - Light cache calculations go back and forth for a while, and on the actual render its really slow.

I'm using todays nightly btw, tried with stable 3.20.02 and the same happens.

Thanks

[jacksc02]

Is Embree on or off?

[vlado]

I'm not sure it's due to Embree itself, there's some weird motion blur going on anyways. The problem seemed to be there with Embree off as well (at least that's what I got from the email exchange).

Best regards,
Vlado

[Moriah]

From what i've found so far, it's an issue with having 2x hairfarm gravity modifiers on the same object and vray's motion blur. So far my solution is to turn off one of them.