What's the best way to render dark scenes with minimal light?

[^Lele^]

Thanks LeLe, but you might have to tone it down for me a bit as I'm still relatively a noob. So to sumarise, you over-exposed by ramping up the exposure on the camera, then reduced the exposure after render using the sliders, but what is this cutoff you're talking about? Where do I find it??
And what should I be doing with my Min shading rate parameter? Leave it on 6?

Everything stays at its default, but i lower the cutoff parameter for lights and shaders.
If the scene is *very* dark, like the part on the back of that teapot, then i will likely also need to lower the noise threshold in the sampling settings, but only in the case V-Ray still misses some parts entirely (so, not by default!).
I posted you two maxscript lines that will lower the cutoffs (without setting them to 0.0, or the render may take very long) for all vrayMaterials and all VrayLights.
Set the value to 0.001 and execute again to get your default cutoff values back.

[dylan86.exe]

Yep, it's cutoffs and/or noise threshold.
Try executing these two lines, and rerender.
If it still shows issues, lower noise threshold further until it's gone.
I do not think you'll need to raise the max subdivs, as where V-Ray was able to find stuff it cleaned it very nicely.

for m in (getclassinstances vraymtl) do m.option_cutOff=0.0001
for l in (getclassinstances vrayLight) do m.cutoffThreshold=0.0001

Do i just copy and paste here?:

[^Lele^]

you could.
or right-mouse click on that little pink/white window, and choose "open editor"
Paste the lines there (and in case save out the.ms file) and then choose "Tools -> Evaluate All", or press ctrl+e to the same effect.

[dylan86.exe]

you could.
or right-mouse click on that little pink/white window, and choose "open editor"
Paste the lines there (and in case save out the.ms file) and then choose "Tools -> Evaluate All", or press ctrl+e to the same effect.

Wow! It's turned out so much better!! Thanks LeLe! Now I can get on with making it look half decent and stop worrying about the technical stuff.

[dylan86.exe]

Sample rate isn't as clean but it's still rendering. Why hasn't Chaos group got an adjustment for Cutoff? Why do I need to do it via script?

[^Lele^]

Sample rate isn't as clean but it's still rendering. Why hasn't Chaos group got an adjustment for Cutoff? Why do I need to do it via script?

We may end up finding a solution to this issue, but if we did, we'd be the first to.
It's very situational, and not quite obvious to get around of. Well, at least without paying a very high price renderTime-wise.

[^Lele^]

Wow! It's turned out so much better!! Thanks LeLe! Now I can get on with making it look half decent and stop worrying about the technical stuff.

It looks like it may need even lower a cutoff, but make sure you try the shader's one first. (wall, right side of the right speaker, likewise some carpeting in the nooks and crannies.).
Alternatively, brighten the exposure (say, by 2X) and revert back after rendering (multiplying by 0.5, or dividing back by 2. Sorry for being pedantic, here.)

[dylan86.exe]

It looks like it may need even lower a cutoff, but make sure you try the shader's one first. (wall, right side of the right speaker, likewise some carpeting in the nooks and crannies.).
Alternatively, brighten the exposure (say, by 2X) and revert back after rendering (multiplying by 0.5, or dividing back by 2. Sorry for being pedantic, here.)

Lowering the noise won't be of any help?? It's currently at .003

[^Lele^]

It looks to me as if noise threshold is quite fine.
As an experiment, try and set the cutoff values to 0.0 in those two script lines, and render a crop of the problematic bits with the render settings you currently have.
Then you'll know if you need lower cutoff, or lower NT.

[dylan86.exe]

It looks to me as if noise threshold is quite fine.
As an experiment, try and set the cutoff values to 0.0 in those two script lines, and render a crop of the problematic bits with the render settings you currently have.
Then you'll know if you need lower cutoff, or lower NT.

Ok getting closer! Noise value of .003, cutoff at 0 (as you said) and 100 subdivs for sampler with 6 min shading rate.. still a bit of noise going on but not quite as bad. I changed my lighting also for a better effect. This is the only lighting in the scene and with no post adjustments.
But you can see the noise in the corners...

[^Lele^]

Umh, then it may be good to lower Noise Threshold.
I chiefly look at the fact that the sampleRate is pure blue (ie. around min subdivs. In other words, it's too happy too soon.) where the noisy parts are.
Had i had a chance to colorpick an EXR i may have saved us all a bit of to and fro, admittedly, sorry for not asking for it sooner. :P
So, back up to defaults (0.001) for cutoffs, and lower noise threshold to, say, 0.001.
You WILL pay a price for it where the red in the SR RE already is, as everywhere else, but it will pick up what right now is missing entirely.

Once that's done, check if there are, at the edges of dark gradients, sharp boundaries: those will be a cue for you to lower cut-offs, and at that point, perhaps just for the light(s) in question, rather than everywhere else.

EDIT:Looking at how the light flux spreads, i have half a feeling there may be some odd gamma behaviour going on, which would make the NT/Cutoff job a bit of a which hunt. Are you rendering under LWF, with the 3ds Max gamma active?

[dylan86.exe]

Umh, then it may be good to lower Noise Threshold.
I chiefly look at the fact that the sampleRate is pure blue (ie. around min subdivs. In other words, it's too happy too soon.) where the noisy parts are.
Had i had a chance to colorpick an EXR i may have saved us all a bit of to and fro, admittedly, sorry for not asking for it sooner. :P
So, back up to defaults (0.001) for cutoffs, and lower noise threshold to, say, 0.001.
You WILL pay a price for it where the red in the SR RE already is, as everywhere else, but it will pick up what right now is missing entirely.

Once that's done, check if there are, at the edges of dark gradients, sharp boundaries: those will be a cue for you to lower cut-offs, and at that point, perhaps just for the light(s) in question, rather than everywhere else.

EDIT:Looking at how the light flux spreads, i have half a feeling there may be some odd gamma behaviour going on, which would make the NT/Cutoff job a bit of a which hunt. Are you rendering under LWF, with the 3ds Max gamma active?

Ok this is with a NT of .001. 200 subdivs. Cutoff at .001. I cant get rid of this noise
It's fine around the lights for some reason but worse the further away from the light source.
My gamma settings are default for max with max gamma settings active...

Is there not enough light or something? I don't want to add more lights because it won't look good but maybe I need to change my camera exposure settings?
Or increase subdivs for the lights themselves?

[^Lele^]

I'd have to take a look at the scene to be sure.
Feel free to send it to me on my chaosgroup email.

[dylan86.exe]

Can't find your email. You can download the scene here: https://drive.google.com/open?id=1-J...gjpYOB2ijCviEA

[^Lele^]

On it, thanks!