Understanding DMC Sampler

[Morne]

@vance3d

Try this as an approach when optimizing:

1. Put on a grey override and hide all scene lights, turn off GI. Turn on default lights in the global switches so you get nothing but a boring grey render in your viewport. Use your sample rate element and max adaptive dmc control until you get clean enough edges on your geometry and get a nice looking sample rate with red only where it’s needed.
2. Turn off default lights, turn on your scene lights and gi. Leave your grey override on and add in the raw lighting and raw global illumination passes. You know that your AA is probably in a good place now so lets not touch that. The sample rate element might go red again due to your lights or GI adding in noise but don’t touch your AA. Try instead adding in more subdivs to your light sources so in the controls of the lights themselves and in the subdivs of brute force GI if you’re using that. Change those settings until your raw light and raw GI are nice and clean (if you use irmap and LC instead of touching brute force then the raw gi is less important) and now when you go back to your sample rate then you should be back to having red only along the edges and blue everywhere else.
3. Turn off your material override and turn on the reflection, raw reflection, refraction and raw refraction elements. Again since these will likely be noisy, your sample rate element will go more red due to the aa sampler trying to clean up noisy materials. Again leave your AA as is, and gradually increase your material reflection / refraction settings until the render elements look clean and your sample rate has returned down to the usual red edge, blue everywhere else type of look.

I’m on an interior project at the moment where I went for this approach. I can’t show any visuals unfortunately.

So in my tests I rendered at 720p. I started of with IRmap, but then thought I would push it and started over with BF.
My AA is 1, 6
To clean rawlight I had to set the Lights subs between 64 and 128 for various lights. Lights are NOT set to store with ir and also NOT set as skylight portal. Most of them are set to invisible and to NOT affect reflections.
To clean the GI I went with 196 BF subs

With the grey override, everything looked super clean and at 720 it rendered about 1 and half hours. Perfect sample rates and RAW passes etc.

OK Perfect.
I previously set the material samples for glossy things between 64 and 128 to clean it up with IRmap, but when switching to BF I just left it like that.
OK so instead of testing how the sample rate would look now that I switched OFF override, I thought I would just render. While I’m at it I thought ok settings seem pretty good, let me while I’m at it push the resolution up to 4K.

OK so previously with the override at 720 a perfect render took 1,5 hours.

NOW:
Without the override and at 4K everything looks super clean and looks AWESOME!. Just my RAWReflection has some noise in it, but I have to nicely look to see it.
Yes! everything is perfect?
Almost, the part that rendered looks great.

MAJOR PROBLEM!?! After 15 hours rendering it did only about 5% and the estimate said still another 300 Hours to Go!
:(:(

Aaarrggg!

Any thoughts? I Would love to get this to work with BF.

Suggestions, comments, and general sympathy welcome