Vray 3.6 low CPU Utilization

[gkolln]

We have noticed rendering scenes with 3.6 that we are getting low CPU utilization. We were rendering the exact same scene with 3.5 and it was using 100% CPU.

Anyone else having these issues?

[nikolay.kusht]

Does this issue occur only on a specific scene? It would be best if you could send it to us for investigation at support@chaosgroup.com. Also give us more details about your render settings.

[gkolln]

HI Nikolay, It is happening on some very large scenes so it will be hard to send them. But to give you some more info we are using BF LC and adaptive lighting. I am about to try without adaptive to see if that makes a difference. There is no motion blur or DOF. What we have just found out is that it is only on our really high core computers in the farm - the ones with 72 cores. It is also not on all scenes.

We did have some issues with Crossmap on these high core machines in the past but the areas where the CPU's slow down are quite basic geometry and materials.

[svetlozar.draganov]

If the issues doesn't occur on every scene then it is most likely related to something specific in the scene which will make the troubleshooting very difficult without a scene.
Did you notice any similarities in all scenes that replicates the issue which are missing from the ones that works as expected, for example using a specific V-Ray features or a 3rd party plugin?
Is there any difference between Bucket or Progressive Image Sampler?
Did you notice something unusual in the V-Ray Messages window / log file?
Can you give us more information about your rendering setup, are you using V-Ray DR or Render Manager etc.

Looking forward to hearing from you.

[gkolln]

Hi Svetlozar,

It seems that the issue is related to Crossmap again. I didn't think this would be the case as it was fixed by the Vizpark guys previously but it seems it has come up again with the latest Vray. I have let them know about it and I will post an update when we have a fixed version. At the moment our workaround is to use Multitexture instead of crossmap.

[svetlozar.draganov]

That's very useful to know, thak you a lot for sharing it.
Keep us posted for any updates from Crossmap side, especially if it turns out that V-ray is involved somehow.

[rivoli]

I recently had a similar problem, with scenes randomly starting to render using as low as 1% or 2% of all available cpus. switching from progressive to bucket doesn't make any difference, light cache building is affected as well.
I think I nailed down the problem to random railclone objects in scene, might be one in several or even a few. once disabled everything goes back to normal. even though I can't understand why this happens with scenes which work just fine until then, with no change to any of these railclone objects whatsoever.
should post on itoo's forums as well, I reckon, as I can't quite tell if the problem is more on their side or vray's.

[vizuall]

I've found same problem ill try to prepare the scene and send it .@gkolin I was checking scene and render preset and what I observed turnig off embre solved this problem.

[gkolln]

Vizuall - thats good to know - on our scenes as soon as we replace crossmap all is back to 100% CPU.

[vizuall]

I havent got any crossmap ,but maybe multitexture use same bercon libraries.