render times slow down dramatically after little changes

[damiano_corradini]

Hello, I use V-Ray for Sketchup and I'm having this problem:
when I start my PC, when I open my file and immediately start the render, the rendering times are normal.




But after even just a few small changes (for example, I added this cube with a generic material applied, outside the rendering point of view)




If I relaunch the render, the times become drastically longer, even though the settings are the same as before



The only way to coe back having good time rendering is to turn off my PC and re-open the file.

Here is a benchmark of my graphic card before the first rendering attempt



This is happening with all the different files i'm working on, i tried to post the pack project of the file, but a warning sais "error uploading image"

Thanks to everyone who can help me

[tsvetomira.girginova]

Dear damiano_corradini, hello.

Could you please try to switch GPU driver version to 552.44?
The reason is explained in some recent forum threads, one of them is this.
Noticed are complaints exactly on RTX, will be a helpful test on your side.

Waiting for your confirmation.

Best regards,
TS

[damiano_corradini]

unfortunately installing the drivers you indicated did not solve the problem.

here is the render made as soon as the file was opened (41.9 sec)



and here is the render after adding a small cube with a simple material (14 min)



here is a new benchmark with the installed drivers

[natalia.gruzdova]

Hello Damiano,

Thank you for the test. To investigate further I would like to ask you to share one of your scenes, so we could test it on our side. For that please archive the scene with the Pack Project tool (Extensions > V-Ray > Pack Project tool) and open a ticket (request type: Product usage questions or issues) where you can upload it.

Additionally try and share results:

• Are you able to reproduce the same issue in a new simple scene?
• Is it reproducible in one of your projects using RTX but change Texture Mode from Compressed textures to Full-size textures (example).
• Alternatively, try rendering with CUDA render engine instead of RTX (example) - does it make any difference?

Thank you in advance.

[damiano_corradini]

Hello Natalia,
i just opened the ticket as you suggested.

In addition here are the results of the testes you asked:
- in a simple scene i'm not having the same problem
- With the "full size texture" mode there are no differences, the issue persist
- Using CUDA i'm not having the problem, but in some scene i cannot use CUDA (for example when i'm using a displacement texture)

render with RTX



render with CUDA

[natalia.gruzdova]

I would like to share an update on this case.

Thanks to the cooperation from Damiano we were able to identify an issue with GPU memory usage for the materials preview.
When material preview in Asset Editor is set to GPU mode it uses a high amount of VRAM. Which consequently leads to less memory available for rendering, and when memory ceiling is hit render becomes slower. The issue is logged internally as WEBUI-7263.

In the meantime it was advised to change the preview mode to CPU.