GPU while rendering works only at 15%

[Jiri.Matys]

Hi,

I want to render one animation for client on GPU. Everything looks great, scene looks almost the same as on CPU, perfect. But when I hit render on GPU, it is super slow and I found out my GPU works only at 15%. It should be around 95% if I remember correctly. Where is a problem, why it is so slow?
I have VRay 5.20.23, GTX 1080 8GB and Win 10. Driver is 516.94. Scene is not so heavy so it fit in VRam without any problem.
How I can fix that please?

[Jiri.Matys]

And now I found out that in Light Cache pass GPU works around 100%. But in rendering it works around 2-15%, it is terribly slow.

[Jiri.Matys]

Please, anybody?

[nicolas_fuminier]

Hello Jiri.Matys

How do you know it's only working at 15% of your CG full load ?
Do you check it with the windows tool ? Because windows task manager cannot monitor properly the real load of your graphic card.

First you can try to enable the "CUDA" layout in the windows task manager and see if it's more usefull than the "3D" tool who is not suitable at all.
Second you can use a better tool to monitor your CG load as MSI afterbuner or EVGA Precision who can tell you the clock speed of your CG, the real RTX or CUDA usage etc.

[Jiri.Matys]

Yes, you are right, I totally forget about this. With HWInfo GPU works on 100%.

What borthers me and why I was confusd about this 15% load of GPU is because when I start hybrid render with CPU and GPU, my CPU finished a lot of buckets but my GPU didnt finish a single one. I dont know why.
Now I am testing it again so I will see.

[Jiri.Matys]

So it finish some now but its much slower then 2990WX.

[nicolas_fuminier]

There may be many reasons why GPU rendering will not be as "fast" as one might wish.

Some ideas,

- You have a 1080, the graphics card is 6 years old and starting to suffer from its age,
- The 1080 can only render in CUDA and doesn't have the RTX technology which increases overall performance by 15-30% depending on the scene characteristics.
- Rendering in hybrid (GPU + CPU) forces you to render in Buckets. For the GPU the fastest rendering mode is progressive and not Bucket.
- Depending on the nature of your scene, the GPU can force some options or not have access to some optimization that are only available in CPU

Best,

[Jiri.Matys]

Thanks for all suggestions.
I bought 3090 in the morning so tomorrow I will see.

[Muhammed_Hamed]

Thanks nicolas_fuminier for your help, spot on
An RTX 3090 will be a lot faster using RTX mode and progressive sampler type

Best,
Muhammed

[Jiri.Matys]

Nevermind

[Muhammed_Hamed]

With your 3090 you should enable RTX mode in the performance tab under Devices Select



With your 1080 it is best to stick to Cuda + CPU

Best,
Muhammed

[Jiri.Matys]

Yes, I saw it right after I post a message.