Shadowcatcher artefacts

[build]

Hi.

We are working on a set of furniture objects which need shadow and a transparent background. We now have the problem that the shadow is not very smooth. Instead of a flowing transition, the shadow stops rather pixelated. Has anybody an idea why it is like this? and how to solve this?



Thank you.

[romullus]

Try to render longer, or use denoiser to reduce noise in shadowed area.

[build]

Noise level is below 1 and full denoising enabled.

[burnin]

Do you mean the shadow on the backboard?
I believe that would depend on material & performance render settings, since that area is only lit by indirect lighting/GI.

[build]

We have a studio setup with 4 light sources. But only the one from the top is casting shadows. All others are shadowcatcher illuminator. We only have a shadowcatcher material for the surface the table stands on. The shadow around the table ends not smooth but rather pixelated. And this is the problem. It should fade.

[sprayer]

Doing product renders i was always struggle with Shadowcatcher noise, and denoiser only make it worse imho, you start to see patterns.
Rendering just stop clear the noise on some point in Shadowcatcher, maybe it because of fix of noise in shadows what was implemented.

[burnin]

We have a studio setup with 4 light sources. But only the one from the top is casting shadows. All others are shadowcatcher illuminator. We only have a shadowcatcher material for the surface the table stands on. The shadow around the table ends not smooth but rather pixelated. And this is the problem. It should fade.

Oh, it would really help, if you'd provide a simple mockup, a test scene to investigate the issue.

[build]

I reported this to the Corona support team now. Let's see what they can figure out.

[maru]

Suggested some tips, let's see if it helps. :)

[build]

I tested the settings. It looks much better now. Thank you!

Here are the recommendations we followed. Maybe somebody else will need them:
1) Go to your shadowcatcher material and make its backplate color darker - this will reduce global illumination in your scene and in turn will reduce overall noise.
2) Go to your shadowcatcher material and increase "shadow amount" value - I can see in your scene it is set to 0,1 and this additionally increases the brightness of GI. I suggest using value of 1 or more.
3) Do all lights in your scene need to have "shadowcatcher illuminator" option enabled? If this option is enabled in a light, not only shadows are included in the alpha channel generated by the shadowcatcher, but also the direct lighting coming from that light. This is useful, for example, if you are rendering a car in a garage, where the garage is a 2D backplate, and you want its headlights to cast light on the 2D backplate garage. But I am not 100% sure if this is needed in your case.
4) Go to Render Setup > Performance and increase GIvsAA balance value from the default 16 to 32 (but no any higher!) - this should make the noise resolve a bit faster at the cost of anti-aliasing quality.

We changed the background and added just a horizontal plane which covers the whole viewport as shadow catcher. This gives us now a new strange effect in the background which I don't understand...
Here a preview with the new introduces "black belt"

[burnin]

Either use a backdrop
or
apply same material in "Render Settings > Scene Environment > Direct Visibility Override (checkbox ON)" that is used with Shadowcatcher.

& Here's a mockup // which could have saved you lots of time, if you'd just share some love ;) study well

[build]

Here are the settings I used for the render. I already used a background override.

The background has a solid black color. In the scene layout, there is no background here. Just a large plane with a shadowcatcher material. It looks a bit like a horizon. But where is this coming from?

Regarding your example rendering, I want to give a little comment.
If you place your picture on a solid background that is slightly larger than the rendering, you can see that there is an edge around it. With the Shadowcatcher material there are a lot of scattered shadows that fill the whole image. This makes it quite difficult to create object visualizations with a transparent background where only the pure object-related shadows are visible.
The lights that cast shadows need to be calibrated exactly so that the shadow only appears up to a certain area. It would be helpful if you could specify something like a threshold value to hide these very weak (and perhaps not really existing) shadows.
It looks more like a problem with transparency in Shadowcatcher material to me.

[burnin]

Here are the settings I used for the render. I already used a background override.

The background has a solid black color. In the scene layout, there is no background here. Just a large plane with a shadowcatcher material. It looks a bit like a horizon. But where is this coming from?

Regarding your example rendering, I want to give a little comment.
If you place your picture on a solid background that is slightly larger than the rendering, you can see that there is an edge around it. With the Shadowcatcher material there are a lot of scattered shadows that fill the whole image. This makes it quite difficult to create object visualizations with a transparent background where only the pure object-related shadows are visible.
The lights that cast shadows need to be calibrated exactly so that the shadow only appears up to a certain area. It would be helpful if you could specify something like a threshold value to hide these very weak (and perhaps not really existing) shadows.
It looks more like a problem with transparency in Shadowcatcher material to me.

:D
Well, of course my dear!
When seeking problems, one will always find one!
It's universal Law. There's no doubt about it. PEBCAK being most common one. ;)

Anyways, check your Light Directionality - for therein lies thy shadow of doubt. ;)

Also, if you're seeking for a different or more complex solutions, to have full control in post, you can always use Compositing tag, Object Buffers, Multipass... to mask the stuff - separate image into main object, its shadows and the background - then do final compositing as you please.

e.g


PS
oh, totally missed it, you're on 3DS Max... my mistake & condolances ;)

[sprayer]

you forget to change backplate color in shadowcathcer, it's gray by default, it  should be the same as your background, and note what this color is effect to exposure value

[build]

This is how it looks from the distance.

We have the solid white object, the table, in the center, including the small shadows from the top light. And then we have another white solid ring around. But where is this coming from? There is no geometry here. And no light source which can cast such a shadow onto the shadowcatcher material!