VRay NEXT - very noisy shadows, Adaptive HDRI bugs, slow render time.

[Karol.Osinski]

Hi everybody,
I am working on the quite particular interior scene. It is traditional chinese guest house with not too many artificial lights to lit the interior. We want to keep. My main source of light was suppose to be a HDRI from outside (no direct sun though), although in order to bring enough light inside I had too boost intensity quite a bit which brought too much color from the HDRI map inside (strong green + blue).

In order fix it I left the HDRI intensity low and created a big rect outside to bring more diffused light.

Anyway…my main problem is that the shadow areas are VERY slow to render and very noisy, and it is not the first time I see VRay really struggling with shadowed areas and we want to keep the lighting in this room very subtle.
My settings are as follow:
BF + LC (1500 subdivs)
MSR :6
Max subdivs: 64
Treshold: 0.012

It took 4 hours to render on i9 7900x + 2990x, there aren’t many complicated materials (maybe apart of wood which is Blend MTL with the lacqured coating).
As you can see, the shadowed areas are full of colored noise. Another problem is those strange lines visible in RawLight pass and RGB… - is it (AGAIN) something about Adaptive HDRI?

Any tips of how to deal with it?

[Muhammed_Hamed]

Use LC subdivs of 3000

It is fine if you use high intensity on your domelight, maybe try a physical sky inside your domelight this time and see how it goes (some HDRIs can be slowers to render than others)
And disable that rectangle light you are using(which might block part of your HDRI), your render settings are fine honestly
Max subdivs of 50 should be enough, and noise threshold of 0.01 with bucket mode
Everything else should be left at defaults

Make sure to add a GI render element and direct lighting, relfection, specular and sample rate
they will be handy to know where the noise is coming from
Your interior is quite tricky because of the tiny windows, let me know how this goes..