Bug with Phoenix FD in GPU RTX renders

[GregCooper]

I'm seeing this with every sim I try to render with vray GPU when using RTX. As per screenshots, certain frames don't appear to be creating the mesh correctly at render time and this can result in weird dark artifacts that flicker during animations. This could have something to do with motion blur as I think the problem isn't there with motion blur disabled. Issue doesn't exist with CUDA. I logged this as a support request a few days ago as an issue with Vray GPU (request no 349-680-8313) but haven't had a reply or a download of the scene files that I uploaded. I'm now wondering if its something to do with Phoenix as it only seems to be happening on Phoenix sims. Also the phoenix team seems to respond a lot quicker to forum posts than Vray support requests

[Svetlin.Nikolov]

Hey, thanks, we are looking at it....

[Paul Oblomov]

Heh, I was told - it can't be reproduced. Two months ago.

[Svetlin.Nikolov]

Paul, not sure this info is helpful to anyone... A large portion of what you report can't be reproduced because you rarely provide proper steps or scenes, and often it takes much more time to track down than the average report. Still, some of your setups do contain real issues that are fixed and this makes the software better, so thank you for that!

Greg's scene showed some artifacts on one of our machines, so hopefully the gpu guys will be able to track them down and fix them. Me or the other guys will update the thread when we know more...

[Paul Oblomov]

I'm a humble person and I understand that cases are different, so don't praise me so much!

It is very interesting to watch the evolution of bugs, how they can wiggle and say, a year and a half, slip out of sight. But then (I relate this to the recent bitcoin crash, of course) it suddenly manages to be caught and destroyed!

With me it's exactly the opposite, I meet them every day, almost. Already we say hello as buddies, I'm thinking of inviting them over for dinner.

Among the variety of my "bug buddies," this is a real gem. He knows how to hide.

[Svetlin.Nikolov]

Hmm, is this the issue that could not be reproduced? How do we make it reproduce?

I have sent you this page a few times already, but here is the kind of information that could really help in reproducing and fixing an issue: https://docs.chaosgroup.com/display/...o+Report+a+Bug

[Paul Oblomov]

The first time I was told it was not confirmed. Thank you for your interest! I'll try my luck a second time then.

Sim, render, max 22, rtx 3090. Drivers, vray\phx version - doesn't matter. It was even in internal alpha build, from last year.

[georgi.zhekov]

Thanks a lot for the reports, finally we managed to reproduce it. Looks like it happens only on Nvidia 3xxx cards when you're rendering with Motion Blur in RTX mode. As a workaround for now you can render in CUDA mode.

We will let you know when we have some progress on that.

As additional info - can you share which GPU drivers are you using?

Thanks!

[GregCooper]

Thanks a lot for the reports, finally we managed to reproduce it. Looks like it happens only on Nvidia 3xxx cards when you're rendering with Motion Blur in RTX mode. As a workaround for now you can render in CUDA mode.

We will let you know when we have some progress on that.

As additional info - can you share which GPU drivers are you using?

Thanks!

Hey Georgi,

Yeah that sounds about right, I've only got a 30 series system to test on but I noticed it wasn't there with motion blur disabled. I think I mentioned my drivers in the support request but using the recommended 471.11. This bug has been around for a bit as I spotted it back in March, just didn't have time to report it then. Let me know once there's a fix. Thanks!

[Paul Oblomov]

Mine is 471.41

[GregCooper]

Hey there. Any update on this?

[georgi.zhekov]

Not yet I'm afraid. Will write here as soon as we have something.

[squintnic]

have just run into this issue....

another big L for vray GPU!

classic, start new job and another undiscovered bug

insane

vray gpu is NOT production ready

*(using 3090s)

[Svetlin.Nikolov]

Hey squintnic , does switching from RTX to CUDA work for you as a workaround?

[GregCooper]

Yeah I'm seeing this issue in more scenes now, some with very basic materials, and without even any phoenix sims in the scene. There's some serious bug with RTX in the current code. It seems to happen on random frames, so this basically means I can't risk rendering with RTX enabled in animated sequences at the moment.