Lot of Issues with GPU materials preview

[javierrentas]

I use GPU preview mainly because we are rendering in GPU all the time. I want to be sure that the behavior of the materials in the Assets editor will be the same as in the render. However, I have a lot of issues with the GPU preview, some times is super slow, hands, incorrect results.
I have to switch to CPU and then back to GPU to get the correct result in GPU.

https://www.screencast.com/t/6ET3w9x...t/6ET3w9xwpEwK
V-Ray 5.2

[konstantin_chaos]

Hi javierrentas,

One of the things to note about the GPU preview is that the first time a new version is installed the preview renderer will take a while to compile the GPU Engine Kernals.
It should be quite fast after that.

Can you give me an example of when the preview is slow or shows incorrect results?
Does this happen with specific materials?

Another thing I'd check is which devices are used for the preview:


If the global configuration is used you should go to the GPU Device Selection UI that is automatically installed with V-Ray and make sure the correct devices are selected.
Note that if C++/CPU is selected instead you are using only your CPU in CUDA mode which can be slow depending on your hardware specifications.

Konstantin

[javierrentas]

The slow down usually happens with refractive materials and when we have a lot of materials in our scene. That bothers me, but I could deal with that. However, as you could see in the video, I get the wrong look sometimes and need to manually switch from CPU and then go back to GPU.
In my setting, I have "Use the Global configuration" Is that the correct setting? For the GPU device Selection, I have selected my CPU and my 2 A6000.

[konstantin_chaos]

Sorry but I can't see the video.
Can you share it again?

[javierrentas]

This is a gif with the issue I'm having. I hope this helps.
Thanks!

[konstantin_chaos]

This is a gif with the issue I'm having. I hope this helps.
Thanks!

OK, now I see it.
As I mentioned in the other thread this is a known issue (in V-Ray Core).
Some of the new Translucency properties will not get updated during interactive rendering.
This has nothing to do with the GPU engine - the same can be observed using CPU.
It is also not a problem of the preview - regular interactive renders will give you the same behavior.

Changing back and forth between GPU and CPU is basically restarting the render process and hence fixing the issue.
You can achieve the same by clicking on the Stop icon and then on the Play one (the icons are on the small preview toolbar).

We'll do our best to improve the way Translucency works in interactive.

Regards,
Konstantin

[javierrentas]

Good to know. Thank you!