How remove noise in automatic mode in VRay 3.3?

[Jiri.Matys]

HI,

automatic calculations of subdivs is great and computing is much faster. But what I can do when I wanna better quality - less noise? I have an exterior scene, can see to interior and there is too much noise for me. I tried to lower Noise treshold, but nothing really change (and it was a greatest gamechanger in standard subdiv mode). Tried to change Min shading rate, but again nothing happen. Tried to change Min and Max subdivs, there is a change and less noise, but not as good as I expect. And when I change those parameters more it already not occurred such a change.

[vlado]

Can you show me, or even share that part of the scene? The things that you mentioned should affect the noise levels, so maybe there is something else going on.

Best regards,
Vlado

[Morne]

If you have an exterior and you can see into the interior, check that you enabled "affect shadows - all channels" on refraction for the glass. If you forgot this, V-Ray will have a harder time cleaning up the interior as less light is "streaming" in through the windows

[Jiri.Matys]

Thanks Morne, try this.

But now I realize I forget to lower Color Threshold and it seem it helped.

[Jiri.Matys]

There is still the same amount of light in interior. I have lights in inteior where windows are to light the interior. If I delete those light, interior is almost black. All channels option didnt help, interior is still almost black wihtout supporting lights.

You can see how it looks with supporting lights at windows. Wihtout them interior is almost black (dont have picture saved, sorry).

[3LP]

I have the exact same issue with a scene I'm working on ATM :


Note : The facade of the BLD is camera mapping so take that out of the equation

As you can see, the wall inside with the big pano hanging is way more noisy than all all the rest of the shot.

Stan

[vlado]

I really got confused who is having what problems Guys, can you start different threads for your own issues?

Jiri, did you finally solve or your problem or not?

Best regards,
Vlado

[LudvikKoutny]

So here's the thing:

With the new solution, you need to be able to estimate secondary vs primary rays complexity of your scene. This is the most tricky part, but it's like that for pretty much any other renderer, and there's no exact rulebook on how to go about it, it just requires some training time and intuition.

In a nutshell, secondary ray effects include glossy reflections, glossy refractions, SSS, any kind of area lights (lights with soft shadow) and GI, are considered branching effects. For those, you need to increase min. shading rate. So for example for complex interior scene with lots of area lights, GI and glossy reflections going on, you may need MSR as high as 16.

Primary ray effects are antialiasing, DoF and Motion blur. Scenes with heavy DoF and/or motion blur do not require as high MSR, as most of the sampling should be spent on DoF/MB. Therefore you may not want to go high with MSR there. Also, if your scenes are really complex geometry-wise, such as lot's of grass and foliage, hair, etc... just very fine geometry, you may want to keep MSR lower (around 6-10) as well, to have more sampling spent on primary ray effects.

So that's a bit of theory behind - and now you may be asking how is it related to the problem above... right?

Well, in order to have even noise distribution, you first need to make sure your MSR is balanced right. Once done, you can proceed to the next step: balancing noise threshold with Max AA subdivs.

Basically, if your part of image is noisy, you need to be able to identify if noise comes from lack of primary rays, or secondary rays. In this case it's most likely secondary rays, so you should proceed as follows:

First you raise MSR, but not get too wild about it.

If that does not help, then most likely, V-Ray stops rendering entire image because it ran out of pass (aa subdivs) limit. So you need to increase Max AA subdivs.

But sometimes, just throwing more passes at the picture may not be efficient, so once you find that increasing Max AA subdivs did help to resolve your noise, you should slowly start to increase noise threshold, so that subtle noise amount is even on the entire image, sometimes values as high as 0.01 or 0.02 are acceptable. The idea here is that once we have noise on the difficult parts of the image under control, at the same time we want to make sure we do not have our less difficult parts of image too oversampled - too clean, way above noise level eye can distinguish.

You should never try to go with noise threshold under 0.005. This value already generally means extremely clean image, unless you render super low-light scene. In general, for best speed/quality ratio, I would suggest value around 0.01 for final production quality.

So, this thing could be wrapped in a few steps:

1, Is the noise coming from primary or secondary rays? If primary rays (AA, DOF or MB) then lower MSR, if secondary rays (glossy stuff, GI, area lights, SSS) then increase MSR

2, If increasing MSR increases noise in AA, DOF or MB too much, put it back. If decreasing MSR increases noise in glossy refl/refr, area lights, GI or SSS too much, then put it back

3, Once optimal MSR is found, image is still noisy even though noise threshold value is at production quality setting (0.005) then simply start to raise Max AA subdivs until it's clean enough. If some areas are still noisy, you may want to refer back to step 1, and make sure MSR is set up properly.

4, If you finally have enough Max AA subdivs to render clean image, but it is taking too long, then simply start to increase noise threshold slowly up to the point noise on the image is even, and right on the threshold of acceptable level.


Of course, there are also a great ways to make scene as difficult for V-Ray to render as possible, such as placing very strong light source very close to bright (and/or reflective) surfaces, creating hotspots for GI to sample. Those require some more experience and skill to handle correctly, but there is no silver bullet renderer on the market yet, so any will require some amount of technical skill. This particular case can be resolved by lowering max. ray intensity at the expense of light transport accuracy.

[vlado]

I would actually really really (really!) leave the MSR alone In fact, I'll probably hide it in some of the next builds.

Attached is an .ods spreadsheet where I rendered a bunch of scenes with varying complexity (interiors/exteriors and so on) with different MSR settings. You can see that 6-8 is a good value for many scenes. While for some scenes lowering it or increasing a little it may reduce render times by some percent, for other scenes incorrect MSR can lead to huge render time increases.

The spreadsheet does not reflect the most recent changes in V-Ray for some of the scenes, but it can still show you that there is not much benefit to be gained by straying too much from the default.

Best regards,
Vlado

[LudvikKoutny]

Hmm,

that is quite interesting. I always suggested to people to stay within 4-16 range. I would never recommend going over or under that, but spreadsheet shows 8 seems to be quite the sweet spot. That being said, I've encountered quite a few scenes lately where increasing MSR shown steady improvement in noise levels after same rendertime. Especially interior scene with sunset sunlight and not very large window openings. In such scenes, difference between default and increased MSR to reach same noise level could be I guess up to 50% of total rendertime in favor of increased MSR (16 in that case).

But then again, I agree that for many people it would make sense to leave MSR alone as estimating shading vs eye ray complexity of the scenes is not something everyone can do, and even for experienced people, it can be misleading sometimes.

EDIT: I also wanted to say I would really keep MSR there (maybe under expert mode) until adaptive MSR is production ready. I am afraid just setting it to a rigid default and hiding it could make handling noise in some scenes a bit more difficult.

[vlado]

In such scenes, difference between default and increased MSR to reach same noise level could be I guess up to 50% of total rendertime in favor of increased MSR (16 in that case).

I would very much like to see such a scene

Best regards,
Vlado

[LudvikKoutny]

Just mailed you the scene

[Jiri.Matys]

I really got confused who is having what problems Guys, can you start different threads for your own issues?

Jiri, did you finally solve or your problem or not?

Best regards,
Vlado

As I wrote, change Color Threshold from 0,01 to something lower solve it - noise was much less. If I have any trouble when I compute final scene, I will let you know.

[Jiri.Matys]

Vlado, why Color Threshold and Noise Threshold are not linked anymore?

[vlado]

Vlado, why Color Threshold and Noise Threshold are not linked anymore?

Because it didn't really make any sense. The noise threshold for the DMC sampler is used only for secondary effects (reflections, GI) and not always at that. The default value of 0.005 is good for practically all cases and there is little to be gained by adjusting it.

The color threshold for the image sampler on the other hand makes a lot of sense to be adjustable.

Best regards,
Vlado