LightMix with empty denoised Lightselect causes weird lighting issues

[NOOKTA]

Hello,

I just found a weird thing and wanted it to share. Obviously the solution is to turn it off or delete, but it shouldn't have any effect at all, no? Also sometimes you lose the overview and its towards the (messy) end of an project.

Sometimes when having an empty Lightselect pass in the light mix, it causes some weird things to happen in the image. I've encountered this before and with the current project I had some extra time to investigate more.

1. create simple scene (I also attached one)
2. add light mix and light select passes
3. make sure to add an empty light select pass
4. check "apply denoising"
4. turn on denoising (only happens with Intel CPU AI)
5. render
6. in my example scene you have to crank the empty pass up real high, around 500000. In my other project it happens also with the value 1 (snapshot attached)

This happens in Corona Frame Buffer inside Cinema4D and also with the CIE standalone.

Full-speed non-debug version
Build timestamp: Sep 26 2019 13:07:24
Version: 4 hotfix 3 (core 4 (Hotfix 3))
Cinema version: R21.026 Cinema 4D (single-license)
Plugin status: Plugin successfully loaded
Win10 Pro / 1903 / 18362.476

Anybody got an idea what happens here? As I said, there is an obvious solution to this, I'm just interested.

Cheers,

Ara

[PROH]

Hi. Two things:
1 Cranking any light in lightmixer up by 500000 is NOT recommended and will always introduce noise.
2 Asking an AI denoiser to denoise pure noise will naturally cause an overly "artistic" result.

Just my 2 cent

[NOOKTA]

Hi PROH,

thanks for your answer.

1. the effect only happens in the test scene with 500000, I couldn't reproduce it any other way. My other snapshot shows the same issue with the value of 1.

2. But I am asking the AI denoiser to denoise a black image, no? I'm not sure I understand how the denoising of light select passes work. Do they look at the final image "as reference" or do they only look at the pass itself?

[maru]

This is an issue of the denoiser you are using, not Corona.
This is fixed for the Intel denoiser in their newest version, and I think for NVIDIA it's the same too.
The fix is included in Corona 5 for 3ds Max, so it should be also there in the upcoming C4D version.

[Beanzvision]

Hi Ara, Can you please test this with the latest release V5 RC3 and let me know the outcome?
https://drive.google.com/drive/folders/1BxlBSWEkpZSR-54EHJGkoONNW20DYPBB

[NOOKTA]

Hey Bengamin,

it has gotten better, meaning in the scene from my initial post I have to use a ridiculously high value to have the effect visible. For my other scene I provided a snapshot. Again, there is a simple workaround/fix from the user side, I guess other bugs/issues have priorities to be fixed ;)

Best,

Ara

PS.: The project is still running, once it's done I will try to upload it for you guys to take a better look at.