Low lighting areas noise

[sicrum]

Hi guys

I am new to this forum and Corona render.

I think my question is very popular, but I am pretty sure that every scene has it's own reason for noisy areas on final renders.
Below is my render.

Summary details and questions:
1) 1600x1200, 180 passes, 2 h 30 mins. My PC is i7 2600, 16 GB RAM - is that normal time or should I look for heavy materials/lights in the scene? What passes number is good with scene like mine?
2) Lighting.  There is VRayHDRI with HDRI map in Corona environment slot. CoronaPortalMtl in the windows. No holes behind the camera. 3 corona spherical lights inside the ceiling light. 2 corona IES lights to the left on the camera (not on the render)
3) Curtains. CoronaMtl with bitmap opacity mask, transcluency and AlphaMode = "Always Transparent"
4) Ceiling is white with 0.7 level, no reflection. Walls are Glossines 0.4 and Reflection 55 and with bump

As you may see there is noise in the corners at the top of the table and on ceilings.
Walls are also looks more noisy rather than bumpy with glossy reflection.
Also, colors are unnatural. But most likely photoshop will help.

Will appreciate any advices.

Let me know if you need any info regarding the scene.

This is full size link: http://s020.radikal.ru/i713/1605/8a/287251a1dfa2.jpg

[FrostKiwi]

Your setup is fine and correct.
I presume you are still on Corona 1.3 and not on the daily releases.
This is 100% GI noise and you can either increase AAvsGI to send sample more GI rays, or... the recommended version... Upgrade to 1.4 daily or wait a week till 1.4 release.
In 1.4 there is adaptivity implemented, which should pickup on that noise and sample the noise away, long before 180 passes. Or even the denoise function which can just outright denoise.

If you need an immediate solution without rerender, you may region render and paste in photoshop. the noisy area.
Also, you can decrease MSI, incase that noise stems from strong rays not being averaged out over time, due to their strength vs the low shadow area samples.

As for the colors, if you do correct PBR workflow with all textures being 50-180 RGB, you will indeed get an ugly washed out look, which requires tonemapping to look nice. But look on the bright side, it's difficult making a a punchy unrealistic image punchy and realistic, then a realistic and washed out image look punchy and realistic.

edit: dat rug looks damn nice :D

[cecofuli]

Try this:

Remove the curtains,
Delete the glass windows,
Add a portal on the window
Use use Corona Sky
Override the material with a simple RGB 180-180-180
turn off the lamps and the monitor
Remove the carpet
MSI= 10
Maybe GI VS AA 24

And see what happens. I think you will have less noise
Now, turn on the material, lights etc... And you will find where is the problem.

Good luck

[sicrum]

Guys, thanks for your replies.

I will try your suggestions

[sicrum]

Try this:

Remove the curtains,
Delete the glass windows,
Add a portal on the window
Use use Corona Sky
Override the material with a simple RGB 180-180-180
turn off the lamps and the monitor
Remove the carpet
MSI= 10
Maybe GI VS AA 24

And see what happens. I think you will have less noise
Now, turn on the material, lights etc... And you will find where is the problem.

Good luck

Applied these steps and got  strange result. White dots inside a window.
I thought that something wrong with window frame and replaced it with simple extruded spline which intersects wall so that light cannot came from there.

Any ideas?

[sicrum]

How can I remove previous post?

Here is 100 passes, no lights but Corona Sky, with portal in the window. Still looks ugly :(

[romullus]

Make sure you using portals in a right way: https://coronarenderer.freshdesk.com/support/solutions/articles/5000501660-how-to-use-light-portals-in-corona-

What's that thing that blocks most light in window opening? You should definitely get rid of it.

[mitviz]

i would advice just using a regular rectangular light and set it to invisitble instead of a portal, it looks way better and gets rid of the issues you are having

[romullus]

i would advice just using a regular rectangular light and set it to invisitble instead of a portal, it looks way better and gets rid of the issues you are having

It's better not to give advise at all, than give bad advise. Putting big light in window opening maybe was good in old days, but certainly not novadays. Putting light source in enviroment, is all that needed for Corona to give great results. Additional sky portals may be beneficial in some circumstances, but not crucial.

[sicrum]

sorry, last picture was my fault. I forgot to add portal to exclusions when use global material overriding

[mitviz]

i would advice just using a regular rectangular light and set it to invisitble instead of a portal, it looks way better and gets rid of the issues you are having

It's better not to give advise at all, than give bad advise. Putting big light in window opening maybe was good in old days, but certainly not novadays. Putting light source in enviroment, is all that needed for Corona to give great results. Additional sky portals may be beneficial in some circumstances, but not crucial.

actually there are many scenes where putting a light there is needed, in cases where there is little lighting to be used inside a room or when you don't want the exterior really blown out, using a light portal doesn't give me what i need most times and since you think its bad advice then i would advise the person who is having the issues to give it a try for himself, it might be bad advice and an old way to work but i am old school and it works for me

[PROH]

I agree with romullus. There is a window + some artificial interior lights. That should be more than enough to make this scene work. The problem here could very well be in the scene setup, or the HDRI, so an additional artificial "window light" would probably only clutter things more.

[maru]

actually there are many scenes where putting a light there is needed, in cases where there is little lighting to be used inside a room or when you don't want the exterior really blown out, using a light portal doesn't give me what i need most times and since you think its bad advice then i would advise the person who is having the issues to give it a try for himself, it might be bad advice and an old way to work but i am old school and it works for me

It is not a solution. It is a bad workaround. You will get completely different, and most importantly inaccurate results.

[mitviz]

actually there are many scenes where putting a light there is needed, in cases where there is little lighting to be used inside a room or when you don't want the exterior really blown out, using a light portal doesn't give me what i need most times and since you think its bad advice then i would advise the person who is having the issues to give it a try for himself, it might be bad advice and an old way to work but i am old school and it works for me

It is not a solution. It is a bad workaround. You will get completely different, and most importantly inaccurate results.
[/quot
Thats true but for ne it seems to work and i get great lighting in most cases

[romullus]

But did you tried to adopt new workflow, maybe it would work even better?