I tried searching for a way to change the dedicated GPU for denoising (either nvidia denoiser or the vray one), but couldnt find any info.
Does anybody know?
Also, how much memory does the denoiser eat?
Sometimes when my scene is packed and almost all vram is full, denoiser wont work. I thought about changing the used GPU to my display GPU, which is a GTX 1070.
Try setting env var
VRAY_OCL_DENOISER_DEVICES=1070
Than restart 3ds Max (or the PC, just to be safe) and see if this helps.
This works for the V-Ray denoiser only (has no effect on the NVIDIA one).
The V-Ray denoiser is very memory efficient - 20-30 MB RAM. The NVIDIA one can use >1GB. Memory efficiency of the NVIDIA denoiser is better in V-Ray Next, Update 1.
Best,
Blago.
Ok, thanks.
and there is no way to choose the gpu for my preferred method, the Nvidia one?
1gb is a lot… But the 1070 could certainly handle that…
Nvidia doesn’t do elements. Have you tried the Topax AI Denoiser in post-production? Slow but really good.
There could be, but I am not aware of such atm.
Best,
Blago.
If you are not aware, who else would be? 
I haven’t. I’ll check out, thanks.
so you denoise with the vray denoiser or just with topax?
What’s your noise threshold usually?
You can only specify the device to be used for denoising with the standalone denoiser tool that comes with the V-Ray installation, but not in the Max/Maya UI. You can instruct it to use a specific GPU or all compatible GPUs. Here’s some docs on it: Chaos Docs
When it comes to choosing between optix and the V-Ray denoiser, it’s good to consider their advantages and weaknesses.
The Optix denoiser is blazing fast, but will produce flickering in animation and compositing back the render elements (if denoised with it) may be inconsistent. It’s a great tool for fast noiseless feedback in IPR.
The V-Ray denosier is consistent and can blend between frames in animation, but takes more time to compute. This makes it great for denoising the final frames. It also works in a batch command-line mode and is available as a plugin for Nuke.
Here’s some info on the two denoising engines: Chaos Docs
ok, but why is that we cannot choose? could be surely coded, no?
recently I am doing a lot of archviz, completing everything in the VFB. With a consistent noise threshold I found that the nvidia denoiser works pretty well, even when rerendering with some changes. So I would love to use it as I found that I need more samples/lower threshold for the vray denoiser.
for animation I would obvivously choose the vray one, but for single frames, nvidia denoiser is brilliant imo
There is no way to choose particular device for the Optix denoiser for now. Your case seems pretty valid and I’ll make a note to see if it’s possible to be implemented.
cool. and nvidia denoiser is not supported in standalone, right?
could that be implemented?
The Nvidia denoiser is not available as a standalone tool. It’s somewhat uncertain if it makes sense to add it, since it’s intended to be used for previews, and is not really suitable for final frames.
Mmh, as I said I’m using regularly for finals too. Didn’t have a problem yet…I can see the potential problems though…
buti think it would be a great feature.
Can the Nvidia denoiser also work without render elements?
A few render elements are there to guide it, if that’s what you mean. Or do you mean if it can be used to denoise render elements?
I meant, it would be interesting to use the denoiser in the standalone version on its own. it is AI driven, so I thought it would maybe get better results than the vray denoiser, which needs the elements.
I wouldn’t hold my breath 
Best,
Blago.
Well, I do need to breath eventually 
Coming back to this (and I am still on Vray Next), I saw that in Houdini you can choose which card to use for the nvidia denoiser:
Is it possible now for us too? I would really like to use a different card for that.
Yes, it should be in the latest hotfix of Next.