Reflection from mirror causes noise

[ous_gt]

I can't figure this one out. The only place i have noise is the part reflects the mirror. Is there any known reason for this?

[ous_gt]

Well actually some other parts are kinda noisy, too. I guess the scene is entirely noisy but we can only see it on the dark reflective surfaces. Anyway this image is after 250 passes so it should've been clear by now, right? What could be the reason?

[CeBeP]

Its not about mirror, its about dark corner. U have to set Path Tracing Samples 16-32 - it will give u less passes, but less noise on every pass either.

[Ludvik Koutny]

I think the noise in this case is caused by environment light being partially occluded by those blinds in windows. It is a lot easier for shadow rays to sample one large square window, than dozens of narrow stripes. My suggestion would be to raise light samples multiplier, and see how that goes...

[maru]

Ous_gt, Are you using portals behind those blinds and are you using PT+HD? (sorry, I'm not able to download the scene right now)

Rawalanche, I think raising LSM could actually make darker areas more noisy, because more samples would be devoted to direct light and this would cause less samples in darker areas during the same time of rendering. I would suggest setting LSM to 1.0. :)

[ous_gt]

I'm using portals and yes, PT + HD

[ous_gt]

I've tried changing almost anything in corona renderer settings, didn't help. I'm making a small crop render of the noisy part, i've been reading all the forum to find an answer, and changed almost anything, but couldn't find the solution.

[rafpug]

Hello

You can indicate the points
where the image appears this artifact?

you do not notice from your smartphone

Greats
Raf

[ous_gt]

In the second picture i attached, almost everywhere is noisy. Try to zoom in on your smartphone. I mean it's not that bad, but after 250-300 passes, i expect it to be clearer, and the thing is, it never gets clear. No matter how long i wait. So i need to change something obviously, but i don't know what. I've tried to change almost everything in the settings but didn't help.

[ous_gt]

Here's a thought, i was using corona sky multi 4 to make it brighter. That might be the reason. Testing with normal settings..

-nope it's not that.

[maru]

I downloaded the scene and I can see you have some really strange geometry in it and overlapping faces (for example portals are overlapping with walls). Your portals are facing wrong direction so they DON'T WORK AT ALL.

Portals should also cover the whole window hole. It's pointless to leave a hole, this kills the whole idea of portals.

You have to be careful with stuff like this in Corona, try to keep everything technically perfect and realistic.

Case closed. ;)

[Ludvik Koutny]

I downloaded the scene and I can see you have some really strange geometry in it and overlapping faces (for example portals are overlapping with walls). Your portals are facing wrong direction so they DON'T WORK AT ALL.

Portals should also cover the whole window hole. It's pointless to leave a hole, this kills the whole idea of portals.

You have to be careful with stuff like this in Corona, try to keep everything technically perfect and realistic.

Case closed. ;)

I never knew portals in Corona depend on surface normal direction...  do you have any tests to back it up? :)

[maru]

Uh? Just place a portal in any scene. It emits light only in one direction. I usually add portals like this: extrude face(s) to form a window hole, remove the top face(s), cap it so there is only one face, detach this capping face. And then you have to apply "normal" modifier or else it won't work.


shit, am I wrong again? :(

yes

[Ondra]

you also don't have to cover whole window, they are effective even if covering openings only partially.

[Polymax]

you also don't have to cover whole window, they are effective even if covering openings only partially.

This new for me! How work portal algorithm?
Ah, maybe,  portal farction is work here (0.75 default)
How work portal fraction? Why default = 0.75?

[ous_gt]

Thanks for all your interest. So if the problem is not the placing of the portals, what is?

Portals weren't placed nicely at first, but while you're looking, i fixed it already. So that shouldn't be the problem.

Actually i'm gonna ask a real simple question. If your albedos are fine, how money passes should it take to clear the image?

If it's taking too long to clear up, what can be the reason besides albedo?

I thought it was about 150 passes. With this scene it almost clears up at 300 passes. Is this normal?

I've tried to render a high res. one, about 3800*2100. It was OK after 250 passes but it took 9 hours.

Now i'm testing it with the same settings with the res 1920*1080. Let's see when it clears up. Maybe i fixed it already somehow.

[Ondra]

This new for me! How work portal algorithm?
Ah, maybe,  portal farction is work here (0.75 default)
How work portal fraction? Why default = 0.75?

Corona uses multiple importance sampling (MIS) to optimally combine direct light samples from BRDF and from lights. This means, that even when one of your strategies is completely or partially useless (because of incorrectly placed portals), the other strategy compensates for that. So the rendering stays unbiased and still gives good results.

Portal fraction is the fraction of samples fow which to use portals. Higher = portals have bigger effect (either positive or negative). Values between 0.25 - 0.75 are conservative, meaning your render will probably not go wrong (slow) because of portals.

[Polymax]

Ok, thanx for the clarification, now I understood.

[rafpug]

In the second picture i attached, almost everywhere is noisy. Try to zoom in on your smartphone. I mean it's not that bad, but after 250-300 passes, i expect it to be clearer, and the thing is, it never gets clear. No matter how long i wait. So i need to change something obviously, but i don't know what. I've tried to change almost everything in the settings but didn't help.

Hello ous_gt
Yesterday I did some tests!

Gradient Maps to glossiness (... play with dark colors, and review the settings right...)
 
These days I have little time for a job that expires


We read them in the next

Greats
Raf