C4D - much noise

[Designerman77]

Hey guys at Corona,

I have a scene that - in my opinion - shows up way too much noise, even at noise level 3.

In other scenes I experienced much less noise at the same or even bigger resolution.
Any idea what could be the problem?
Scene materials are more-less the same as always, nothing crazy reflecting or so.

Tried to exclude possible candidates that could cause the noise: windows glass, portals, change wall material, empty the scene, etc...

With portals, the scene has even more noise !


Also: please notice the weird "ray switching" on the upper wall section when portals are added.
I had already reported that to you guys over a year ago!
Would be great to finally get rid of this problem which makes portals unusable with HDRs.


I gladly attach the complete scene if you send me a link for it.


Thanks in advance

[TomG]

Well, Corona 6 will be doing away with portals, thanks to a new environment lighting sampler. Watch the daily builds for when that appears in Corona for Cinema 4D.

Also, the noise limit is an average across the whole scene, so some scenes may just need to render for longer (ie a lower noise limit) to clear up noise in certain locations. And last, what denoising are you using? Looks like denoising would clear this up nicely, and at a guess none is being used?

There are tips on dealing with noise at https://help.c4d.corona-renderer.com/support/solutions/articles/5000501983-how-to-get-rid-of-excessive-noise-

And last, which version of C4D, Corona, OS, etc?

[Designerman77]

Hey Tom, thanks a lot for your quick reply.

In those images, no denoising was used - since I wanted you guys to see the raw result at 3% noise... which is super noisy after my experience with all other render scenes I´ve done over years.

Regarding my system: R20, iMac Pro 8core 3,2 GHz, OS: High Sierra 10.13.6


Speaking of portals: that's great news about Corona 6. So portals will be obsolete in version 6?
At the moment I am still on version 4.
Have not changed to 5 since I'm in the middle of a huge customer project right now... and you know... that's never a good time to experiment... though this problem made me consider trying For 5.


Regarding longer render times for cleaning up the scene: even changing from 3% noise to 2% results in way longer render times.
In my tests it literally doubled the render time.



BTW: the room is lit with an HDR.
In the other room, lit mainly by corona lights, reaching 3% noise takes almost 10 times less calculation time.

[TomG]

Yes, portals will be unnecessary in Corona 6 (and in fact options to add them will be gone). Sampling from an HDRI is exactly what is improved with the new Env Sampler.

As to the noise, this is exactly what denoising is for :) Some places in a scene will take a long time to clean up, and that's how and why the denoiser can reduce render times by up to 70%. Highly recommended in this case.

As for noise limit, yes, it's non-linear, it will take significantly longer to reach 2% than 3%, and so on. But, denoising is the planned solution for that, you should be fine hitting 3% and denoising will take care of the rest - you just need to get it "clean enough" and let 0.5 to 0.6 denoising take it from there :)

[TomG]

PS in the other room with lights in it, the corners will be hit by direct lighting, faster and easier to calculate. Here in this room, light only reaches the corners via bouncing around the room, hence it takes longer to clean up. Be sure to check the help desk page too for various settings you could try.

[Designerman77]

Yes, portals will be unnecessary in Corona 6 (and in fact options to add them will be gone). Sampling from an HDRI is exactly what is improved with the new Env Sampler.

As to the noise, this is exactly what denoising is for :) Some places in a scene will take a long time to clean up, and that's how and why the denoiser can reduce render times by up to 70%. Highly recommended in this case.

As for noise limit, yes, it's non-linear, it will take significantly longer to reach 2% than 3%, and so on. But, denoising is the planned solution for that, you should be fine hitting 3% and denoising will take care of the rest - you just need to get it "clean enough" and let 0.5 to 0.6 denoising take it from there :)

Hey Tom, of course I do use the denoiser in my daily work... :)
Just in this example I left the pics raw, so you can estimate the (high) amount of noise at 3% in this specific scene.
And as mentioned - normally 3% plus 50-60% denoiser looks super clean in other scenes... only this specific one seems weird.
I´ll keep on testing... although there is actually no time to test in the middle of a job.
But I hate to just guess and not precisely know things! :)



Regarding the darker areas in scenes, where noise is usually more visible and cleans up longer: I suggested to the devs to create an intelligent denoiser that focuses more on those areas, as soon as the rest of the scene is okay. That would be really cool, in my opinion.

[TomG]

Corona already does that :) It's called Adaptive Sampling, where harder to calculate areas get more processing time. Been in place for a long time :)

EDIT - oh, does that for calculating the lighting. The denoisier is already pretty smart about knowing what to denoise, too.

[Designerman77]

Corona already does that :) It's called Adaptive Sampling, where harder to calculate areas get more processing time. Been in place for a long time :)

EDIT - oh, does that for calculating the lighting. The denoisier is already pretty smart about knowing what to denoise, too.

Okay, cool to know. Maybe to make the sampling even more adaptive? :)))

Ah, while testing two different HDRs: one HDR renders twice as long as the other one to reach 3% noise... although both are from the same HDR-reseller.
Any idea or your own experience on why such a big difference?

Can it be because of the angle of the sun in the different HDRs?
Actually I see no logical reason why this should matter.

[TomG]

Different brightness of light bouncing around the scene from different HDRIs could make a significant difference. No idea on this part, but not all HDRIs are created equal in terms of their format etc. so that could make a difference too (from what I've read, not all are accurately HDRI), so that could make a difference as well. You can always send in the scene and HDRIs via private uploader if you think there's a bug.