Why shadow catcher plane is not entirely transparent?

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1

Hi,

For some reason shadow catcher plane is not entirely transparent. What is it?
I have followed a few tutorials which seems tome pretty clear but I still get same effect each time.

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Thanks

2

Works for me in 2.93.0, you have to toggle transparent in the render settings… Also a heads up, in higher versions:

The Shadow Catcher outputs different results depending on if the Shadow Catcher pass is enabled in Render Layer settings. With the Shadow Catcher pass enabled, all indirect light interactions are captured. With it disabled, a simple approximation is used instead. The simple approximation is used in viewport rendering.

https://docs.blender.org/manual/en/latest/render/cycles/object_settings/object_data.html#visibility

shadow-catcher-transparent
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3

Hey!

Thanks. I have enabled transparent right from the start. Having said that, I work on the 3.2 version. My scene is super simple. Object + Plane (shadow catcher) + HDRI. I just double checked the file and it appears a problem occurs when introducing HDRI light. Object + Plane (shadow catcher) + point light is fine. Sample attached.

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4

Maybe the HDRI is causing a 360 degrees shadow and the darkening you are seeing is actually a correct shadow?

5

If your shadow catcher is showing, it is likely that you turned down the alpha value of whatever material it had. I don’t know why, but when you turn the alpha of a shadow catcher down, the alpha of the shadow gets lighter, but the plane itself does a fade in. It used to be that the way to decrease the shadow was to turn down the alpha. Not the case anymore.

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To be honest I don’t recall changing anything. That’s how it looks.

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7

Shouldn’t shadow catcher ignore HDRI lighting too?

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I’m not sure, haven’t used it since they did the latest changes, but the image you posted looks like it has multiple directional shadows, like the HDRI is being counted. Or the shadow catching is not working properly and some of the plane’s shading is showing.

9

This is procedural HDRI (physical atmosphere) being used. No issue what so ever.

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10

Hmm, not too knowledgeable but I checked with 3.2 and it seems to work fine, there is this:

https://wiki.blender.org/wiki/Reference/Release_Notes/3.0/Cycles#Shadow_Catcher

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11

I just tried the shadow catcher on a fresh scene and it creates shadows from the sky for me. It does it with a solid backround or with an HDRI. This is a realistic behavior and what I would expect. In your first image, maybe it just looks weird because the plane is too small and the shadow reaches the edge?

I think the soft shadowing is not visible in the other images because the strong direct light is drowning it, making it invisible. Especially since the more recent shadow catcher is supposed to use bounce light which could be removing the sky shadows too.

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Thanks for checking it mate :+1: :+1: :+1: To be honest It’s not a big issue for me unless I want to use HDRI with shadow catcher and then export it for the use on the white background. For now I will concentrate on what I can do and hopefully apners will follow later.

1 Like