Cheatsheet: How to get a Cleaner image with SP3

[padre.ayuso]

If the SampleRate shows blue in the noisy areas, lower noise threshold
If the SampleRate shows red in the noisy areas, raise max AA subdivs

In the blue, very blue, but most of the scene is now fine, except for those few things. I have already brought down my color threshold to 0.003, if I keep on lowering it I'll be shooting up my render times quite high and making the reason I got VRay (speed and quality) in the first place quite useless. Anyhow, I'll keep on trying new scenes and see if I can get my head around this one, perhaps there is something I'm not doing, lowering the Color Threshold to .001 did result in a much nicer image, but the time, as I said, was ridiculous.

[Alan Iglesias]

Alan, I find these settings to leave quite a bit of noise. I had to bring down the Color Threshold to 0.003 and because VRay directs the sampling around, some areas ended up nice and some with quite some noise. Any other settings you change around?

Hmmm...no. All three files that I have brought in from 3.2 to 3.3 rendered very clean at 1/24/.01 - and they rendered faster to boot. One was lit by a Dome plus other vray lights, another two by a Dome/HDRI. Maybe I've just been lucky. I'll keep trying new things and see what happens...

-Alan

[eyepiz]

I am having an extreme issue trying to render out things with 3.30.03. I had a large project that was taking 19+ hours, per view, and now a small project is behaving the same way. If someone can look at this, that would be great. Right now, there is no way I can make deadlines with such high render times. I had to run my current scene, though Corona, just to get it to deadline. The Corona render took less then 2 hours. It's probably something I am doing, but I can't figure it out. Also, if it matters, both scenes were started V-Ray prior to upgrading to the new 3X.

Corona took 2 hours for the same render? was there a quality difference? I'm Just curios.. I've been hearing a lot about the speed of Corona. I usually use IM/LC for stills with as of good results as BF/LC and much faster, however, I do use BF/LC for Animations and my render times are significantly longer.

[glorybound]

I can't tell the difference between Corona and V-Ray, however, I have heard that people like Corona better.

Corona took 2 hours for the same render? was there a quality difference? I'm Just curios.. I've been hearing a lot about the speed of Corona. I usually use IM/LC for stills with as of good results as BF/LC and much faster, however, I do use BF/LC for Animations and my render times are significantly longer.

[glorybound]

What it you are seeing red in the shadows, however, the noise isn't an issue, will your render move faster if you decrease your noise threshold? I have an exterior that when zoomed in I see the noise, but nobody will notice. I am seeing red in those shadows, which if I follow the rule of thumb, I should lower the noise threshold. The only reason I would lower it would be if V-Ray would have to work less in those areas.

[padre.ayuso]

What it you are seeing red in the shadows, however, the noise isn't an issue, will your render move faster if you decrease your noise threshold? I have an exterior that when zoomed in I see the noise, but nobody will notice. I am seeing red in those shadows, which if I follow the rule of thumb, I should lower the noise threshold. The only reason I would lower it would be if V-Ray would have to work less in those areas.

Bobby, I think if you see red, you increase the Max Subdivs, not lower the threshold. If you see blue, you lower the threshold if there is noise in the render. I noticed that 3.3 will automatically use however many samples it "thinks" it needs, so increasing the Max Subdivs will only increase the samples in the red areas, not the rest of the areas in the render.

[glorybound]

Gotcha, thanks.

Bobby, I think if you see red, you increase the Max Subdivs, not lower the threshold. If you see blue, you lower the threshold if there is noise in the render. I noticed that 3.3 will automatically use however many samples it "thinks" it needs, so increasing the Max Subdivs will only increase the samples in the red areas, not the rest of the areas in the render.

[padre.ayuso]

Gotcha, thanks.

No problem Bobby! By the way, Happy New year to you and to all Chaos staff and members!

[padre.ayuso]

Hey Lele, lets try this as a theory. I was writing another thread on this when I remembered your Cheatsheet:

So I have been trying out 3.3 and its automatic settings. I have this one interior scene and have been lowering the color threshold more and more to the point of getting it down to .001, for Progressive and for Adaptive rendering methods. Unfortunately, this increases a lot of rendering time to the scene and did not clean my noise much, specially in a flat wall you will notice that you have lots of noise, no matter if you use IR or BF, you will have some noise. Increasing Max Subdivs. to even 100 will not solve your problem since a look at your Sample Rate shows it to be really blue, like dark blue, which means you can shoot millions of samples into the scene but VRay is not using them, as a matter of fact, is not using more than the original it "thinks" it needs to match your Color Threshold when you had it set at 100 or even lower, if you will.

Previously, with your "manual" method, you just had to find out what was causing the noise, was it the GI, was it the reflections, the lights, etc., and increase the samples accordingly. However, Vlado wants to make VRay automatic and not have you think and try and error forever, thus his new workflow. The problem comes when you don't need to increase the Color Threshold any longer or where increasing this will make no difference in your scene except add render time. So for the purpose of my interior scene, I did not need any more samples on my GI, I just needed them on my walls, this is what I did:

This I finalized with Progressive Method:
1. Lower Divide Shading Rate to where needed. I was using IR and could lower it to 2, and it sped up my rendering.
2. Reach the Color Threshold I was happy with. This was 0.005.
3. Increase Min. Subdivisions. This means VRay will shoot a higher minimum of Samples on the scene, whereas 1 is lowest it will go I brought it up to 10 (yes, it may sound like a lot).

Anyhow, this is what I did, it seems logical right now. If anyone has any other suggestion on how to clean noise without reducing Color Threshold down to very low levels increase render times exponentially high, please do let me know.

[^Lele^]

As usual, i'd need a scene to be certain of anything.
My ChaosGroup email will do fine.
It looks like the trick for the wall might have been raising minimum subdivs (so yes, V-Ray will shoot a certain amount of AA rays without adapting), which could be the case if you have very fine detail, or for some reason you're using stuff like VRayDirt on it, which may be cured by a first part of the rendering as "fixed" (ie. with higher min subdivs).
Then again, i am shooting in the dark.
Scene? :P

[padre.ayuso]

I'll send you the scene when I get back to the office. I'm having a long night somewhere else, so I'll get that to you when I get back in. Otherwise, no VRay Dir being used and I think we are right on our conclusions here. Funny enough, I rendered it with IR at medium presets, fixed some settings so I'd not get blotchy ceiling (is mostly whitish color) and it rendered at 3000 pixels in about 1 1/2 hours with Progressive, so I was happy with the result. But I'll let you know better tomorrow.
Best
Alex

[Pixelab]

1. If the SampleRate shows blue in the noisy areas, lower noise threshold
   
2. If the SampleRate shows red in the noisy areas, raise max AA subdivs
   

Ok, but if you want the opposite (faster renders, with obviously more grain) what's the best practice to get the most speed increase for the same amount of grain ?

Increase the noise value or decrease the max AA subdiv ?

Is this the oppsite or am I messing everything ?

1. If the SampleRate shows blue in the noisy areas, lower the max AA subdiv
   
2. If the SampleRate shows red in the noisy areas, increase the noise threshold
   

[^Lele^]

Ok, but if you want the opposite (faster renders, with obviously more grain) what's the best practice to get the most speed increase for the same amount of grain ?

Err, i'd love to know that too.
I think it'd be a much loved feature, eheh. (pulling your leg here! :P)
Unfortunately, if you need to lower rendertime, you will get more grain (let's assume the rendertime setup is optimal, or that no tweaking would make it any better.).
Then again, all you need to do from a setup of say, 1-100, 0.005 for your finals, is to raise the noise threshold.
Set it to 1.0 (yeah, that high!) and see what it does.
Then halve it and rerender, a few times over: you will see how natural the progression in rendertime vs. quality will be.
Or not, in which case do tell!


Edit: boy what an off-topic reply.

YES, your logic is right.
However, there is no need to do so in the first place (hence me understanding apples for pears!) as V-Ray will terminate itself accordingly.
Should there be "hanging" areas, which would want to go all the way to red when a scene is mostly blue, you may be pretty confident there are other issues afoot (a visible sun speck, some odd shader setup, heritage procedural maps not to scale, and so on.) which are forcing V-Ray to keep sampling.
Whether it should automatically stop sampling in those cases, or not, is debatable at best (there are plenty of cases where such intense work is well needed to accomplish specific tasks), so if you feel it's wasting time on areas that can't otherwise be improved, sure, you can limit the max AA and have it stop when you feel it's right to.

[Pixelab]

Err, i'd love to know that too.
Set it to 1.0 (yeah, that high!) and see what it does.
Then halve it and rerender, a few times over: you will see how natural the progression in rendertime vs. quality will be.
Or not, in which case do tell!

Hmm, really funny because a I made a quick test, and doubling the noise thresold and haling the max rate (from 16 to 8 ), gave noisier result for ... a longer rendertime.

An indeed, max rate back to 16 and pushing the noise to 1 do the trick ! I have a nice fog of noise in less than 5 minutes for a 4k, but I can tweak my light setup.

I really like the new "unification" of subdiv across material, light, brute force GI, etc. but with HDRI in direct light on a dome + IM in interior scenes, I have to uncouple the Dome and raise its subdiv to get acceptable noise, unless you have ugly undersampling on the border of the HDRI sharp shadows. And if I lower the global thresold, I almosty lose the speed benefit of working with IM

[^Lele^]

I really like the new "unification" of subdiv across material, light, brute force GI, etc. but with HDRI in direct light on a dome + IM in interior scenes, I have to uncouple the Dome and raise its subdiv to get acceptable noise, unless you have ugly undersampling on the border of the HDRI sharp shadows. And if I lower the global thresold, I almosty lose the speed benefit of working with IM

I am really no big expert in IRMap anymore, i somehow right away favoured the quality benefits, and the pixel-sized noise, to the unrealistically (to my eyes) smooth and splotchy IRMap.

There is no denying it does the trick excellently, especially in complex (lighting-wise) scenes, if one's prepared to do away with some accuracy, but as scene complexity (geometric) grew over the years, i personally found that trying to coax it into working with all the fine detail by now present in any given scene (hair, high-poly geo, and so on) often led me to try and use it as i would a BF solution (hint: you're oversampling the pixel instead of undersampling it.), just i got there after lengthy trial and error sessions, while the BF render would have been well cooked by then.

Give the default BF+LC settings a chance, they may surprise you for speed and quality (you will see indirect shadows you would never have seen in SP2, for example), while not setting you back from IM+LC as much as they used to.
Vlado and the guys did a lot of work on the algorithms in a number of different places (GI Caustics for example), so you may notice a sizeable speed-up in the notoriously slower BF+LC setup as a result of those.