Choppy VFB when moving the window

[JonasNöll]

Hi,

I have the issue that the VFB behaves extremely choppy when moving the window around. This issue exists across different 3ds Max installations (2020,2023,2025) and different V-Ray versions for me.
Is that something specific to my computer or an issue in general? I can't remember it was like this before. It's only for the VFB window.

Video: http://www.jonasnoell.com/downloads/vray/vfb.mp4

Best,
Jonas

[hermit.crab]

Check if the issue is resolved if you add the VRAY_NUM_THREADS=N variable and set one core less. Also, what kind of hardware does your workstation use?

[JonasNöll]

Hi, I'm running a Threadripper 3990X and a RTX 4090, 64GB of RAM.
So you mean I would have to add a SystemVariable name VRAY_NUM_THREADS and give it the value of 63?

[hermit.crab]

So you mean I would have to add a SystemVariable name VRAY_NUM_THREADS and give it the value of 63?

Yeah, exactly.

[JonasNöll]

Hi, nope that doesn't seem to improve anything. I even tried with much lower values.

[JonasNöll]

But I can see that if I move the FrameBuffer and have the TaskManager open then one logical processor is running on 100%. But if I move any other window such as 3ds Max render settings window then they are all idle.

Video: https://www.jonasnoell.com/downloads/vray/vfb2.mp4

[hermit.crab]

The redraw of the VFB, of course, does require some computing, so there will be some CPU utilization, however, it is strange that it is only one core on your end. I tested on an identical CPU and did not run into the issue - the task is split between cores. Is your CPU overclocked? In your task manager, it says the speed is 3.92 GHz, while the base speed is 2.90GHz. If yes, could you try testing with the default speed?

[JonasNöll]

Hi, no not overclocked. I think 2.9 Ghz is the base speed and I guess it can clock individual cores higher if the other cores are not busy. At least that's what I guess, because otherwise I also couldn't explain why it shows a much higher number.

Anyway it seems that the issue resolved itself. So now the window runs smooth and I don't get this single core at 100% anymore. No idea what it was though. I had multiple reboots and it kept on stuttering but now without any reboot it just stopped being stuttery Anyway I will report back in case I get this issue again.

[hermit.crab]

Glad it's resolved. Maybe it's a third-party thing. Do post again in this thread if the issue reappears.