White dots with reflection

[micmac]

Hello,
I have white dots in my reflection (on the ground and on the walls). I don't know how i can resolve this problem.
Do you have any ideas?
Thanks for  your answers.
Best regards

[maru]

Hi,

preview.jpg - after how many passes is this?

I think some of the noise visible in the image is in reflections and some of it is in direct/gi light. How is the glowing material made? (the one which is visible in the reflection) What kind of lights are you using in this scene? Are there glasses in the windows? How is the glass material made?

You could also do this to determine which render settings could be tweaked: https://coronarenderer.freshdesk.com/support/solutions/articles/5000516731

[Ludvik Koutny]

How many lights are there in the scene?

After certain light count is reached, Corona basically switches from fast light solver to slower light solver. Slower one should be able to handle more lights without big rays/s hit, but is not always efficient.

Other problems can be:

Low blur values on the bump maps

Glass with caustics enabled

Light emitters intersecting objects

Emitters close to objects with high albedo

[micmac]

hello maru,
_the render has 100 passes.
_this is a archicad model so i have two plane of glass. one plane is a portal, the other is classic glass mat thin (see the attachement)
_i use rectangular light for the shop (80w)
_"How is the glowing material made" which one? main ground? road? wood?
 

[micmac]

hello rawalanche,
i have almost 400 lights, is it too much?
when you said "low blur values on the bump map" means that i have to put the blur value lower? or higher?
thanks

[maru]

_i use rectangular light for the shop (80w)
_"How is the glowing material made" which one? main ground? road? wood?

ad 1. But what kind of light? Corona light? What are its settings?
ad 2. By glowing material I mean the big advertisement inside the building which is visible in the reflection. But now I think it's just lit by lights, right?

Just for test, could you check if the noise in the ground reflection is still so visible after removing the portals? And after removing the thin glasses?

[Ludvik Koutny]

hello rawalanche,
i have almost 400 lights, is it too much?
when you said "low blur values on the bump map" means that i have to put the blur value lower? or higher?
thanks

Yes, that's the problem. AFAIK light limit is 250. After that, Corona switches to the other solver.

So you can resolve it by using CoronaLights only for important key lights in your scene, and for non important light sources, use CoronaMTL with emission enabled instead.

[micmac]

maru,
you can see the light option in the first post, the "light shop" attachement.
_yes, the big advertisement is lit by light (rectangular).
_ i try to remove portal and i let you know.
_ i try the CESSENTIAL_Direct and CESSENTIAL_Indirect. Results are attached

[maru]

Ok so the noise on wood is clearly visible in direct light. Increasing "light samples multiplier" in render settings should help. I would suggest changing GI vs AA balance to 8 and LSM to 4 as a starting point, this should equalize the quality of GI and direct light, while keeping more or less the same render time. If the noise is still visible, you can for example turn GIvsAA back to 16 and see if it helps.

[Ludvik Koutny]

Ok so the noise on wood is clearly visible in direct light. Increasing "light samples multiplier" in render settings should help. I would suggest changing GI vs AA balance to 8 and LSM to 4 as a starting point, this should equalize the quality of GI and direct light, while keeping more or less the same render time. If the noise is still visible, you can for example turn GIvsAA back to 16 and see if it helps.

That won't help much. As long as you exceed 250 light limit, things will render slow and noisy no matter which knob you twist :)

[micmac]

okay,
_i reduced the number of lights (less than 200).
_the render is done without glass and portals.
_render setup attached.
With this setup, wood looks better but still noisy in the ground reflection!

rawalanche, you told me "Low blur values on the bump maps"
what it means?
thanks

[Ludvik Koutny]

You do not need to completely remove lights, just replace lights that are not important (lights that are not important and not strong) with geometry that has CoronaMTL with emission enabled. If you want lights there, then you should have them there :) Don't let renderer limit you. But use CoronaLights only for important key lights, that are strong.

By low blur value on bump maps i meant blur value which is in map nodes. It's default at 1.0. You should not use too low values like 0.01 in such scenes, because then texture detail can become smaller than pixel and cause fine noise that takes long to resolve, but this is especially important for animation, not as much for still images.

Your direct lighting now looks ok. The reflections are noisy because they are super strong. What is missing is some secondary photographic effect to make it look natural. That usually shows itself as glow or glares on photos.

But before you do that, you should first check if blurring on the textures the wet road is not too low on some of the bitmap nodes, and if bump mapping is not too strong. These could cause it to appear lot more noisy than it needs to be.

You can also now decrease GI/AA balance to 8 so that you have more AA going on which will resolve texture detail better :)

You can also put the glass back. Just make sure it does not have caustics enabled :)

[Ludvik Koutny]

Oh, and you can also increase image filter width in system tab to something like 2.0-2.5. That could help too.

[Ludvik Koutny]

But in general, you should always get those noisy speckles on wet surfaces with strong texture at night when light by strong light source. like on the photo here:

[micmac]

thanks a lot rawalanche,
i 'll take a look at your advice! many thanks!
best regards,