Serious render bug - Animated Mesh with Camera Motion Blur on - Network rendered

[CLF73]

Hi there Chaos Guys
When facing a hard deadlines (Xmas) it becomes quite frustrating to realize some elementary render stuff still doesn't work, more than a year after the GPU engine was first released.
See image for versioning.

Anyway, let me explain.

GPU engine, deforming meshes and camera motion blur has caused all sorts problems for a long time, which I first reported some months back.
https://forums.chaos.com/forum/v-ray...-3-3dsmax-2021
and, no, upping the geometry MB samples in the vray properties, or the camera render settings doesn't fix the issue!
The mesh errors becomes less obvious with more MB samples, but they still persist.

In this current example I have a Skinned Gnome preforming a simple walk cycle.
However when rendered with Camera motion blur on, flipped or missing areas starts to appear on the mesh at random intervals (network rendered).
See video example.

For reference have I included the exact same sequence rendered in CPU

And finally I'll show a secondary weird bug.
When rendering GPU but disabling camera motion blur, then the model won't acknowledge out of frame keyframe behavior?
Switch Cam MB back on, and it starts moving?

Link to 3D file
https://we.tl/t-ECuqYFQWoQ

Any fast help is very much appreciated.

[Martin.Minev]

Hi @CLF73,

Thank you for the report.

Does the first issue occur when you render the file locally with GPU?
We will investigate your file soon and post you an update.

[CLF73]

Hi Martin
Actually the error (flipped or missing areas) also occurs when rendering locally.
I use Render Stacks to submit to farm or locally. So it shouldn't be related to network rendering. Thus you should be able to recreate the error on a single machine rendering the sequence.

Waiting and excited to hear back

[CLF73]

And yes. The problem only occurs when rendering with GPU (RTX or CUDA doesn't matter) and when the Camera motion blur is on.

[CLF73]

Oh, and by the way. Please add to your list, that the render dialog camera motion blur doesn't work either.
No Motion blur can be achieved through the render dialog alone. MB only seems to work when using the camera object, motion blur setting.

[Martin.Minev]

We made tests with camera motion blur on and off, using different Nvidia drivers. In all cases, your scene file renders fine here.
https://drive.google.com/uc?id=1L2FP...8K9dOK8HgiWFoy
(different hdr used)

Could you please let us know more about your setup? Please make a test and render the file locally without RenderStacks.
Please also send us the VRayLog.txt located in the temp folder (type %temp% in file explorer) in our contact form here and mention this thread.

Thanks!

[CLF73]

Aha, very interesting Martin. And thanks for getting back.
I'll send you the more elaborate info later. but for now these are my specs.

Could you please recommend a Nvidia Driver I should try instead of my current?

[CLF73]

Here is a test where I rendered the sequence fully local with standard Max (No RenderStacks)
As you can see the error persists
.

[CLF73]

Here is a local test without the HDRi map activated. So that can be ruled out as well.

[CLF73]

Hi Martin
Do you need more system info from me?

[CLF73]

Update!
CUDA rendering seems to fix the problem.
Contrary to what I thought I already tested and concluded. It seems that switching to CUDA eliminates the MB render bug.


In this example, all I did was switch to CUDA from RTX.

[Martin.Minev]

Hi @CLF73

Thank you for all the tests you made and for the log file.

Your driver is older than our recommended one. Here you can find our current recommended driver. Please could you try updating your driver and make a new test.
Let us know how it goes.

[CLF73]

Hi Martin
That also fixed the problem (similar to switching to CUDA) - Great

[CLF73]

Oh, it didn't post all I wrote. Let me try again.

It worked that I updated the driver. which is great, but unfortunately driver updates has to be coordinated on workstations and farm nodes, so it won't happen within my deadline.
By the way, I was under the impression that Nvidia recommends using studio drivers for creative apps, your recommended driver is game ready driver. Is there a difference from your perspective?

Suggestion.
Since the VRay GPU engine is this dependent on drivers for stable results, I suggest that you include an alert in the render dialog, which informs you if you are running the latest recommended / approved driver, or if you need to update. No matter the root of the problem, this and similar experiences comes across as working with an instable render engine, So I would prioritize making sure people know when they are working outside your recommendations.

The pictures in the previous post. is another issue I came across yesterday. If I place a light parallel to a Matte object vray plane "floor", these weirds lines show up.
I'll check again to see if its also driver related, but if you have time, please make a quick test yourself.

Thank you.

[Martin.Minev]

Glad to hear it works now.

There is no difference for V-Ray GPU using Game-ready drivers or Studio drivers.

V-Ray GPU performs a check for the current driver used and prints a warning in the log if differs from the current recommended (a screenshot here). From the V-Ray Log, you send me it seems like it's not working on your end.
Do you use any firewalls? Also, do you have any specific environment variables for V-Ray set?

Regrading the Matte issues, could you please send me the scene file on the ticket. I will send you a new link.
Thanks.