V-Ray uses only 50% of the CPU while rendering?

[Helldoor]

Hi there,

In February I built a new Render Workstation, in hopes of speeding up my working process. Beside 64GB RAM and a P4000 Quadro GPU, it uses an i9-7980XE CPU with 18 cores, which - as you'd guess - I want to take the most of while rendering.
The last image I rendered was a 4000x2100 exterior with some 20 trees (bounding-box-proxied), grass (V-Ray Fur) and all the other, usual exterior stuff. Only sun as a method of lightning, no other lights. Rendering time on Very High Settings was approx. 5 hours.
During the rendering however, I found out, that the CPU usage is around 50-55%, but never more (see Image attached).
Why is that? And how do I get the engine to use 100%?

Thanks in advance!

[Peter.Chaushev]

Hello,

Have you used V-Ray Swarm?
Do you happen to be using any custom V-Ray environment variables?
Is this standard behavior for all your CPU renders?

Kind regards,
Peter

[Helldoor]

Hi Peter,

thanks for the response.

. No, I didn't use V-Ray Swarm in this case, nor have I used it at all.
. What exactly do You mean by the "custom V-Ray environment variables"? I use V-Ray Sun and Sky with 1.3x Environment (V-Ray Sky).
. That's not really standard - usually, a render will first "fill up" the RAM, then do the Light Cache and after that take up all the 100% of the CPU, while rendering. Using just 50% from the CPU is new to me.

[Peter.Chaushev]

Apologies, I meant a system environment variable, such as VRAY_NUM_THREADS or perhaps custom affinity set for the Rhino process?
Anything unusual in the V-Ray progress log? (button is at the bottom-right corner of the VFB window)

[Helldoor]

Nothing unusual in the system environment either. I don't use distributed rendering and never changed the VRAY_NUM_THREADS manually. To be honest, I thought, that the Envirnonment Variables are a V-Ray for Max thing, as they're not covered in the Chaos Group Docs online on V-Ray for Rhino. Also, typing VRAY_NUM_THREADS in Rhino results in an unknown command.
As for the progress log - I didn't have it open, so I'd probably have to render once more in order to see anything unusual...

[Peter.Chaushev]

To be honest, I thought, that the Envirnonment Variables are a V-Ray for Max thing, as they're not covered in the Chaos Group Docs online on V-Ray for Rhino.
Also, typing VRAY_NUM_THREADS in Rhino results in an unknown command.

Apologies for the confusion! This will be amended.

The variables are set in the Operating System and affect how processes run. They're set through the Windows Control Panel's System properties.
V-Ray Swarm's Web UI configuration and the V-Ray Device Selection tool also modify relevant environment variables.

If you manage to reproduce the low CPU usage reliably, please send an email at support@chaosgroup.com - my colleagues will be able to provide you with live assistance in order to find out the cause of this behavior.

Kind regards,
Peter