Can we specify/limit the number of CPU cores/threads used for a render

[pedersenfocus]

Hi. We are using vRay 3 with 3ds max 2016 and backburner for network rendering. Our PCs / network render nodes are being used by day as workstations and we find they run very slowly while we are rendering, so can we specify the number of cores/threads to be used for a particular rendering job and so leave the remaining cores free to perform task while the operator is working on his/her PC. We have abandoned Maxwell render in favour of vRay but this was one useful feature which we would like to have (or know how to use if it's there) with vRay also.
Thanks.
Jesper Pedersen
www.pedersenfocus.ie

[Dave_Wortley]

There is a hidden render setting for VRay to do this.

renderers.current.system_numThreads which is defaulted to 0, you can set it to anything you want, or you can set affinities in windows task manager.

Remember different machines have different numbers of cores and often it's the RAM usage that will slow your machine down more. Make sure you have Low Thread Priority on as standard for VRay as this frees up a lot of resources without turning off cores.

[pedersenfocus]

Hi Dave,
We'll start by activating "Low thread priority" which was not ticked on our setup. Hopefully that will do it.
Thanks for the tip!
Jesper Pedersen
www.pedersenfocus.ie

[vlado]

V-Ray ignores the renderers.current.system_numThreads setting for backburner rendering, I think. However, you can set the environment variable VRAY_NUM_THREADS=N where N is the number of threads you want V-Ray to use. This can be set on each machine separately depending on how many cores it has. It can also be configured differently for different users on the machine - i.e. the user that backburner runs under, can use a different value than an actual user logged in.

Best regards,
Vlado

[Macker]

Windows task manager will actually do this. If you go to processes and right click 3ds max and select "set affinity" you can choose which CPU cores it uses.

[vlado]

Windows task manager will actually do this. If you go to processes and right click 3ds max and select "set affinity" you can choose which CPU cores it uses.

This might not be possible if the backburner server process is started under another user account and the current user doesn't have sufficient privileges to change the process priority of another user.

Best regards,
Vlado

[AlexP]

you can set the environment variable VRAY_NUM_THREADS=N

Ive tried setting this on the backburner server, but when rendering it still uses all threads?
Ive put it in system variables and user variables.

Anything else I need to do?

[vlado]

Hmm, which V-Ray build?

Best regards,
Vlado

[AlexP]

version 3.20.01