Ok! I’m not getting the result I’m wanting to demonstrate the desired points. Will check with @juangea tomorrow to finish these ones.
3k test images are below:
2.93
3.0
Back
FullRender
@brecht you can credit Statix / redhoot. Its just different monikers I use online.
@JoniMercado note that for color to show up, you need to use the Shadow Catcher render pass. Since just the alpha channel is always going to be grayscale.
@statix, thanks, the video is now in the release notes.
@brecht this is the result I got from the shadow catcher pass. Although this is SUPER awesome, it doesn’t have an alpha channel for me to composite quickly over my other layers.
How can I get just the color information over a transparent background?
The shadow catcher pass must be multiplied with the background. There is an example file here.
https://developer.blender.org/D11172
I should update the release notes and docs with more information about this.
Actually that .blend file is outdated and does not work anymore. But I added a screenshot now to demonstrate how it works:
https://wiki.blender.org/wiki/Reference/Release_Notes/3.0/Cycles#Shadow_Catcher
@brecht I don’t know if multiplying a colored pass it’s a healthy compositor practice.
But this is the result so far:
Assets
Background
ShadowCatcherPass
Compo Image
Original
I don’t know if is there any reason to compare with older versions, colored shadows were impossible at previous versions.
I could update this week the look of the floor. But let me know if this shows what’s needed.
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Multiplying the pass is correct in this case, that’s what it is designed for.
We could indeed not do the comparison with an older version, but rather show the render passes along with the final result.
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I realized that after analyzing the shadow catcher pass, it looks like it’s ready for multiplying.
This is so awesome.
A few considerations I took for the test above.
When I tried to use the textured wall and floor as shadow catchers, the shadow was affected by the base color of those textures. But I don’t know if this should be the desired result. Either way, I didn’t like it and worked on a workaround.
I couldn’t use a default material because the white base color by default affected the indirect lighting over the chair, so I used an 18% reflective material with the roughness and bump maps from the original shader so I could have the bump on the shader as well.
Will organize better the nodes and share them this week.
Thanks for your help and keep the great work.
@brecht I know it’s technically “cheating” to use a fully CG scene to demonstrate the new features of the shadow catcher, but I have created a few for testing. (Note: What I mean by “fully CG scene” is a scene that is made in Blender for both the “real life” image part and the “computer generated shadow catcher” part)
This post can also be used as a resource for things other users can look at for creating a shadow catcher example. @JoniMercado maybe you could find something useful from this?
Here are some ideas I had for showing off the new features in the shadow catcher, but it should probably be remade in a more photo realistic scene:
- CG objects can now cast light into the “real life” image. In Blender 2.93 when a CG object casts light into the scene, it as treated as if it is a “real life” light and as such the lighting will be incorrect. This is fixed with Cycles in Blender 3.X:
“Real life” scene:
Adding an object with the Shadow Catcher 2.93:
Adding an object with the Shadow Catcher 3.X:
- With the old shadow catcher caustics wasn’t caught properly, now it is. Maybe a scene could be made with a glass sculpture with caustics added into the scene via the shadow catcher? Or a disco ball added via the shadow catcher?
Adding Suzzane to the scene using Blender 2.93 shadow catcher:
Adding Suzzane to the scene using Blender 3.X shadow catcher:
- With the old shadow catcher indirect light wasn’t captured. This is fixed with the new shadow catcher. Maybe a scene like the one below could be created? An object being placed indoors in the path of sun light to show off the indirect lighting captured by the shadow catcher? Also, the new shadow catcher seems to handle indoor scenes WAY better than the shadow catcher in Blender 2.93 as can be seen in the images below.
“Real life” scene:
Adding Suzzane to the scene using Blender 2.93 shadow catcher:
Adding Suzzane to the scene using Blender 3.X shadow catcher:
I’m sorry I don’t have any real use cases for the shadow catcher. I don’t usually work on Blender projects and as such haven’t worked on a project that actually makes use of the shadow catcher yet.
I can try and create a scene based on a real life image, but it may not be that great and may not be ready in time for the release notes.
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There’s many things that could be done to create a better shadow catcher example, but I wanted to have the release notes complete a week ago, we’re not going to go through more iterations now. I want to really have the notes complete by Wednesday, if necessary I’ll create the missing renders myself.
@JoniMercado could you attach those renders as PNG files? I’d like to show the “Assets” pass has transparency, with the white background it’s not so clear.
Do you still plan to make an image for the shadow terminator? Or does anyone else here want to contribute it?
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Sorry for creating such bad examples for the new shadow catcher, never imagined I would have that much work this month.
If anyone wants to contribute to the shadow terminator, that would be great too.
Tomorrow I will upload everything I have. Have an excellent monday.
I think the renders you created are great for showing the new shadow catcher, there’s only so much we need to communicate with those images really.
I’ll try to provide a valid example for the shadow terminator, I may have a small character that at could be useful to show this, I’ll upload the pictures later.
Great, we have a shadow terminator image now:
https://wiki.blender.org/wiki/Reference/Release_Notes/3.0/Cycles#Shadow_Terminator
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Hey, you made a cartoon version of yourself! 
But seriously: nice to see our images on top of each other. Always great to be able to contribute to Blender.
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hahaha yes! it just need the beard!
And yes, it’s cool 
and yours is cooler hahaha
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Thanks, but I’m sure my scene took way more time to create than yours, so it’s not a fair comparison. 
And your images serve the purpose very clearly.
TBH the character is obviously modeled for Mesh SubD modeling, I have another version done with sculpt that is much better hehehe but it was no useful for this, but in any case your character is more interesting than mine hahaha
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