Noise help

[subpixelsk]

I´ve got hard time with rendering this interior - as you can see there is slight noise behind the sofa and everywhere.. the reason I´m posting this is that it is fairly low resolution - 1200x720 or smtg like that and I´ve let it render for 2 hours (approximately 600 passes) and while having this set up - GI/AA 32 LSM 1 (as noise doesn´t come from direct light I guess) MSI 20 - i´ve tried different scenarios while trying to maintain rays/sample under 50 .. no ies lights just hdri + sun (and of course I changed hdri to test it few times and even blurred it to reduce the noise) and few lights on the ceiling.. nothing fancy ..I really wish to have clean results and this is not the case I consider render heavy and I had cases in the past when rendering in 3k  resolution and similar lighting condition resulted in cleaner render in comparable time...
My rig - i7 4200k 24gb ram

Thanks a lot for any advice

[Ludvik Koutny]

I don't understand why would you ever care about rays/sample. It's as irrelevant attribute as it gets. Rays/sample depends on how complex your materials are shading-wise, but if they look the way you wan't them, you just can't do any compromises in quality. You can't just decrease rays/sample count without dumbing down your materials other than worsening their quality, and worsening quality is never a solution.

So i would first try to just assign gray diffuse material to everything, to see if the problem is material related, or if it's lighting related. Also, portals, when placed wrong may cause extreme slow downs.

[subpixelsk]

I have no portals in the scene..regarding rays/sample I didn´t know that it is irrelevant ..thought that have read something regarding optimal rays per sample in corona troubleshooting section..In that case I won´t bother with it..I guess I tried that gray material but will try it again

Thank you

[subpixelsk]

I´ve attached two region renders - one with sun/sky (1) and one with sun/hdri (2) ..each of them 500 passes but I am not convinced with the amount of noise especially after such a long render..Is this normal?

[Ludvik Koutny]

How white are you walls? and is there any glass in windows? Anyway, my first try would be to put portal in the small window.

[subpixelsk]

walls are with mtl override 128 grey and yes there is glass made from simple plane and with glass material with no refraction assigned

[subpixelsk]

This is render with portals in small windows.. I tried to lower the intensity of sky and sun to make it more uniform - it is default 1 for both ..this time I let it render for 3 hours and about 1500 passes (about 2mil rays so the speed is quite ok?).. I´m getting mad I don´t think this kind of resolution and not so complex scene should render so long on my rig while noise never converges.. but tell me it´s normal and I will try to accept it :D

[maru]

Could you try rendering without those window blinds (just for test)? I think they may be causing some truble. I would also add portals in all the possible window holes. Here is a guide on portals:
https://coronarenderer.freshdesk.com/support/solutions/articles/5000501660

You can also try to identify whether noise comes from direct or indirect light:
https://coronarenderer.freshdesk.com/support/solutions/articles/5000516731

If after enough passes (AA looks good) you get noise in gi or direct light, this could mean you should increase GI vs AA or LSM.

[subpixelsk]

Maru many thanks - I´ve filled every hole with portal and increased GI/AA to 64 (maybe a bit too much but it pays off) and after 40 mins of rendering the walls look much less noisy as in the example above

[racoonart]

You can also try to identify whether noise comes from direct or indirect light:
https://coronarenderer.freshdesk.com/support/solutions/articles/5000516731

Also make sure you have a look at marus suggestion. If you're coming from another renderer you may think that direct light only includes the sunlight, but actually, the brighter portion of the wall behind the sofa is most likely direct light.