Cheatsheet: How to get a Cleaner image with SP3

[Pixelab]

We can add this to the V-Ray light properties dialog, if that's ok? I really don't want to add another spinner to the light itself.

Best regards,
Vlado

I would be the happiest !

[joconnell]

I could be wrong but if you've left everything at default anyway, the default minimum shading rate of 6 will be a higher amount of shading samples than what the default of 8 in your materials or lights would have, so if you leave everything default, turn on "use local subdivs" and only increase the sudvids on your dome light with the hdri it'll serve the same purpose of concentrating on the quality of the light and leave everything else under the control of your minimum shading rate.

Lele / Vlado - I take it that any of the MSR samples aren't subject to adaptive sampling / early termination? In other words, the benefit of keeping it set to a 6 is that it's not being tested after each single sample to see if your noise threshold is met which makes it able to work faster. The default value of 6 is also low enough that even though early termination isn't kicking in, 6 rays won't cost you that much at all.

[^Lele^]

I could be wrong but if you've left everything at default anyway, the default minimum shading rate of 6 will be a higher amount of shading samples than what the default of 8 in your materials or lights would have, so if you leave everything default, turn on "use local subdivs" and only increase the sudvids on your dome light with the hdri it'll serve the same purpose of concentrating on the quality of the light and leave everything else under the control of your minimum shading rate.

Correct.
Of notice is that because "divide shading subdivs" is on (EDIT: and one REALLY really really wants to leave it ON.), and the defaults for Max aa are quite high (24 and 100 respectively), your subdivs will have to go high indeed to make a difference (ie. with max at 100, you would need over samples on your dome to match an msr of 6.).
Doable, but hardly comfortable.

Lele / Vlado - I take it that any of the MSR samples aren't subject to adaptive sampling / early termination? In other words, the benefit of keeping it set to a 6 is that it's not being tested after each single sample to see if your noise threshold is met which makes it able to work faster. The default value of 6 is also low enough that even though early termination isn't kicking in, 6 rays won't cost you that much at all.

Correct, methinks. I'll defer to the boss for that, though.

[joconnell]

Cheers for the clarifications. I'd imagine that vlado's hesitance for anyone to use high MSR values is down to the difference one might make if they set up a render optimised for something without dof or motion blur (where you'd have lots of plain, simple surfaces that are going to get cleaned off and sampling terminated at aa 1) but then they turn on motion blur and those plain areas will now get far more minimum samples than the 1 they originally stopped at, take a way bigger hit of MSR rays which won't early terminate and the extra sampling data will just get averaged out in the blur of the final image anyway?

[Lupaz]

...no particular character to the lighting can come from tiny windows when sampling a huge spherical BG, so one's better off with a normal arealight behind the window simulating the environment

just to make sure I'm understanding: example... There's a big house with 100 windows. I can place a dome light and I wouldn't need to use light portals on every window. Correct?

[joconnell]

Yes. From what Lele says, light portals were introduced before the dome light was. The domelight has importance sampling to make it far more efficient to sample the hdr, the light portals kind of did the same thing when we were using hdri's in the environment dialog which didn't have importance sampling and was nosier as a result.

In the case of bobby's scene, the size of the windows was a big factor. He had tiny windows and if you consider a hdri which wraps 360 degrees around the entire scene, the windows were so small that they were only able to see a 1 degree section of the hdri. There isn't going to be a huge amount of colour variance in this 1 degree which controls your scene lighting and it's far slower so it was a cleaner solution to just use a simple light plane. If you compare this to a different type of building plan that had very large window sections, they'd be taking in light and colour values from a far bigger section of the hdri so you'd see some difference in the light.

[short cirkuit]

would be awesome if we had another video tutorial to explain all this in laymans terms - would it be possible to do so with a realistic scene that most of us would use (perhaps archviz interior?) instead of a shaderball and other shapes?
A lot of my friends using vray are just like me in terms of the settings and ongoing development.... lost There seems to be a few theories floating about and just when you think you've kind of understood - a curve ball coems and things change a little which affects the way you set up your final renders.

A quick and easy 5 minute tutorial would be soooooooooooo beneficial to us not so bright people Im more of a visual person, reading the forum (which i have about 324 times) just doesnt stick for me.... Vlado/Lele can you do one just like the other one? 35k views im sure theres a lot of people that would benefit from it.... pleaseeee!?
https://www.youtube.com/watch?v=tKaKvWqTFlw

[joconnell]

I'm thinking of doing one - largely based around the ideas behind the samplers and what causes them to need more or less samples. The idea would be that you could look at your scene and what it contains, then be educated as to why certain aspects of it would need either more or less samples. The nice thing is the fundamentals behind vray haven't changed since the early versions, there's just been different methods brought in to make controlling these fundamentals faster and simpler. My hope would be once you understand how vray sees your scene, you'll understand what causes problems and which settings you need to address to fix them. The theory will remain the exact same even as the chaos developers come up with different ways of controlling the various quality settings, you'll always be able to look at your render and figure out what the problem is and which button you'll have to adjust to change things.

[Streetwise]

One point of clarification for me: On Global DMC, the value is set at 1.0, but greyed out. Is that to say that since it's (apparently) turned off, that it's really 0 and on the automatic setting? Or must I activate Use local subdivs and physically set it to 0?

[joconnell]

If use local subdivs isn't turned on, vray ignores pretty much any dmc setting and just applies the shade rate. That 1.0 "subdivs mult" is an overall up and down control for every subdiv setting in your scene but again only if you've got "use local subdivs" turned on, otherwise it does nothing.

Edit - also anywhere you see a control greyed out, it means that setting is currently disabled and has no effect on your render.

[mitviz]

I'm thinking of doing one - largely based around the ideas behind the samplers and what causes them to need more or less samples. The idea would be that you could look at your scene and what it contains, then be educated as to why certain aspects of it would need either more or less samples. The nice thing is the fundamentals behind vray haven't changed since the early versions, there's just been different methods brought in to make controlling these fundamentals faster and simpler. My hope would be once you understand how vray sees your scene, you'll understand what causes problems and which settings you need to address to fix them. The theory will remain the exact same even as the chaos developers come up with different ways of controlling the various quality settings, you'll always be able to look at your render and figure out what the problem is and which button you'll have to adjust to change things.

would be nice, i have one of your tutorials saved for a while now and honestly its one of the best tutorials i have ever seen on clarifying some things in vray, go for it!

[joconnell]

I'd say it'll take a while and be a commercial release somewhere around the 200 dollar mark but if I get all I want in to it it should pay itself back fairly quickly in faster renders or clearer decisions! On the other tutorial, nearly 600,000 poor people have tried to listen to an hour of my monotone voice

[jasonhuang1115]

I'd say it'll take a while and be a commercial release somewhere around the 200 dollar mark but if I get all I want in to it it should pay itself back fairly quickly in faster renders or clearer decisions! On the other tutorial, nearly 600,000 poor people have tried to listen to an hour of my monotone voice

Look forward to the new release John and I was the 1 of 600,000 people...

[short cirkuit]

Looking forward to the tutorial

[king_max]

The dome light has importance sampling of the hdri in it, so it will help rays go in the places which are the most relevant to getting the lighting right.
In that case, as John well pointed out, there is no benefit whatsoever from a light portal, which served/serves the same function the domelight has for general background bitmaps (ie. it will tell vray to walk through the light portal and see what is behind it. That's important, please sample it.)

Using a dome to light an interior from a small aperture is a waste, again as pointed out by John, as the small aperture will anyways let in a beam of the color and intensity behind it, no particular character to the lighting can come from tiny windows when sampling a huge spherical BG, so one's better off with a normal arealight behind the window simulating the environment.

If an interior scene was lit by sun+sky only , now would there be any benefit in putting the vray sky in a dome light instead in the environment slot thus removing the need of any portal lights?