Understanding DMC Sampler

[super gnu]

lovely material on those black chairs by the way.

[re:FORM]

*Drive final shading quality with the MSR at a global level, use the per-object subdivs multiplier to drive it up or down in a relative way to the rest of the shot.

Am I right in thinking this per-object subdivs multiplier isn't implemented in Maya yet?

[Moriah]

*Drive final shading quality with the MSR at a global level, use the per-object subdivs multiplier to drive it up or down in a relative way to the rest of the shot.

I've been trying this workflow on my latest shots and it works wonders, apart from the per-object subdivs multiplier. Most of the noise i have left to clean up comes from 2 objects GI pass, one has refraction, the other doesn't have neither reflection or refraction, pretty basic material. I tried increasing the subdivs mult even to 20-30, and it gets really slow, but it only changes the noise pattern, doesn't clean it up. On other objects below 1 seems to work fine, but i have to go to really low values like < 0.1 to notice a difference. Doing some wrong here?
AA: 1/12 clr: 0.014 / DMC: 0.85 noise: 0.005 / MSR: 64 / Min Samples: 2 / Global subdivs mult: 0 / also lowered all lights/mats subdivs to 1 even though it doesn't make a difference.

Also in this case i tried lowering the MSR to 16 and do AA: 2/12 instead and i noticed a speed ~15% speed increase and better noise.

[vlado]

Am I right in thinking this per-object subdivs multiplier isn't implemented in Maya yet?

It' been in the Maya nightlies for a while.

Best regards,
Vlado

[lightpixel]

Try a recent 3.25 nightly build and see what you get...

Best regards,
Vlado

where can I get these nightly builds...

[Zdravko.Keremidchiev]

Please send us an e-mail to: support@chaosgroup.com

[^Lele^]

Well, yes, I did.
But you could too, just remove the crop and render the whole scene.
Help yourself with a sample rate RE, to debug either the crop or the full region.
The drop in cpu usage may be because of the need to refine only very few pixels at the end (something that does happen.), so even with a small ray bundle, in the crop you may just have too few pixels (ray bundle fo 4, 16 cores, that's a total of 64 samples on all cores. If you have an area just 4 or 5 pixels, you would get many idle cores, unless MSR was forcing insane per-pixel sampling.).
On a whole image, statistically, that's a lot less likely to happen, with "one-pixel" areas to refine being many more at once across the image plane domain than in your crop.

[Morbid Angel]

Also in this case i tried lowering the MSR to 16 and do AA: 2/12 instead and i noticed a speed ~15% speed increase and better noise.

Yeah I wouldn't go that high with msr. I've noticed performance drop actually when using high msr, vs the aa.

[^Lele^]

Yeah I wouldn't go that high with msr. I've noticed performance drop actually when using high msr, vs the aa.

Don't make a RULE of a case.
There's logic behind it, and if your raising MSR meant your renders were slower, it's likely because you had very thin detail, and most of the oversampling done per pixel would have gone to waste at the next camera ray.
Areas without high-frequency geo or texture detail WILL always benefit from tracing more secondary rays than AA rays (actual mileage may vary today, but i demonstrated in another post that AA rays are TEN times slower than shading rays.), for a given sampling amount.
Take the Digital Emily renders i'm doing: MSR helps greatly on the skin, so my SSS doesn't get as many fireflies, but then the specular part, and the eyelashes need absolutely more camera rays to be first well defined (think alpha outline) ideally with lower per cam ray sampling (lower MSR) to make sure i don't waste time on a pixel that may be "not so valid" after a few more iterations.
For skin, i elected to use an MSR of 8, for both sss and spec, and i set the subdivs multiplier to 0.25 for the eyelashes object.
Further, if one has thin geo it's a good idea to shoot a few AA rays no matter what, so a min shading rate higher than 1 (say, 4) helps the later stages threshold against valid data (rather than more estimation and guesswork).

From a logical point of view, when a scene is a completely unknown entity, an MSR of 2 is the best situation to start from.
If some shading time is spent on a pixel which will get later "trumped" by better shading, only one shading ray per pixel more than normal will have been traced, while if the shaded pixel is actually a "valid" one, the added shading ray will help stabilise it.
Chances for gains and wastage are identical.

To sum it up: if there's plenty of thin geo/high-frequency textures raise AA, lower MSR, for everything else, the opposite.

[Morbid Angel]

I hear what you'r saying. Problem for me is that ALL my scenes have high frequency detail all the time

[fco3d]

Sorry guys for waking up this thread one more time.
But I been struggling to adjust my workflow to this "new system" for V Ray, MSR.
I do Arch Viz mostly, interiors and exteriors and I been trying to use more Brute force and hopping I could use it in animation but rendering times and just a killer.
From what I read here, I been playing adjusting MSR up and down in combination with AA. I get better results on interiors when I use high MSR about 18 and lower AA: 1-8 usually, but when I adjust values individually I get better rendering time still.
I noticed that mostly Brute force needs more sample compared with glossy areas. So my only way to increase Brute sample is increasing MSR, if I go AA route renderings time just spike ridiculously. trying to deal with this problem I am ending up with an almost even number for MSR and AA MSR: 13 and AA 1-12, numbers varies but they get closer usually.
I can go per object route, but if it is a scene with many elements, that option seems a little far fetch. is that what you guys do? adjusting MSR per object? doing that does not defeat the purpose of saving time adjusting shader per material?? is not the same?
it would help if you can adjust MSR and AA and be able to increase samples for Brute force separately? Well I guess doing everything manual does that.

your word of wisdom is apresiated.
Fco.

[vlado]

Do you think you can get me a scene to look at to vlado@chaosgroup.com ? The default settings should be good in most cases, but I'm not sure if there's something else in the scene - and talking numbers without a specific example is a bit pointless.

For animations, the irradiance map might still be faster though.

Best regards,
Vlado

[Morne]

ah nevermind...
spoke too soon

[fco3d]

Vlado Thank you, just send you an email.