Shadow Catcher

[mguisado]

Hello and thanks for reading.

I'm sure this is a known subject (it´s even on reddit but unsolved) but I've read and watched tuts and I can't seem get a solution. This image illustrates my problem


So I only want to keep the shadow from the sphere, but don´t know how to do that (and don´t understand why the plane is getting some short of shadowing).

I have also tried enabling the Render layer and black shadows (in the climax of my confusion I even tried applying the Object tag needed to either the sphere or the plane, even both).

This is the scene for the image above
https://www.dropbox.com/s/yfi7d824zxzya ... h.c4d?dl=0

Thanks in advance for any help.

[bepeg4d]

Hi,
about the shadow catcher version, your plane is simply too small, if you double the dimensions, everything is working as expected:

You could use also a Floor object to avoid the issues with dimensions.
Anyway, the Shadow Catcher/Matte option was the only way in the past, and can give issues with emitters.
Better to use the Render Layer workflow, in this way you can use a Glossy material for the floor, to obtain also the reflections. Since by default the whole geometry is at Layer 1, you only need to add an Octane Object tag to the sphere, set a different Layer ID number (eg.2), and enable the same layer ID in the Render Passes tab, with the Shadows, and Reflections options active:

Happy GPU Rendering,
ciao Beppe

[mguisado]

Grazie mille Beppe for replying.

So I was able to see the shadow just like you showed using the Render layer approach, but the problem was when rendering to EXR (still doesn't work, but that's another battle for me to look into).

It works fine if I render a PSD

[bepeg4d]

Hi,
sorry but your screenshot is not visible, please use the Upload attachment button, thanks.
ciao Beppe

[DartFrog]

Hello and thanks for reading.

I'm sure this is a known subject (it´s even on reddit but unsolved) but I've read and watched tuts and I can't seem get a solution. This image illustrates my problem


So I only want to keep the shadow from the sphere, but don´t know how to do that (and don´t understand why the plane is getting some short of shadowing).

I have also tried enabling the Render layer and black shadows (in the climax of my confusion I even tried applying the Object tag needed to either the sphere or the plane, even both).

This is the scene for the image above
https://www.dropbox.com/s/yfi7d824zxzya ... h.c4d?dl=0

Thanks in advance for any help.

I have the same problem in 3Dsmax. The shadow is there how I want it, But it tints the ground a small percentage and you can't get rid of it.

[Hatsize7]

Is it possible to create an invisible object which creates shadow? Like an inverse shadow catcher: a shadow maker.
I want this object NOT to be included in the alpha.
I found this thread (viewtopic.php?f=56&t=68214&p=342112&hil ... ER#p342112), but it didn't help.
Tried all variations of activating alpha channel, shadow catcher, visibility, opacity, didn't work, the object is either visible in alpha or not casting a shadow. If I deactivate alpha shadow from the kernel, that's the closest I can get, but then the invisible material's self-shadow is showing up in the alpha channel (the object itself doesn't)
I couldn't find more info on this in the manual. Anybody has an idea? Ahmet? bepeg4D?
Thank you!

[aoktar]

What's up with "camera visibility=off" on object tag?

[bepeg4d]

Hi,
please consider that the Matte/Shadow catcher option is not perfect, and has some limitations, for example if there is an emitter material in the scene.
Much better to avoid to use it, replace the Diffuse material with a Glossy material, and use the Render Layer technique instead:
http://www.aoktar.com/octane/RenderLayer.html
In this way you can obtain shadows and also reflections on the ground.
ciao Beppe

[Hatsize7]

What is up with "camera visiblity off" is that the object doesn't get subtracted from the alpha channel.
So: on material: Shadow catcher ON, affect alpha OFF
Kernel: Alpha shadows OFF
Beauty image is good, but alpha channel shows building's self shadows
Turning the camera visibility off the object's contour is not removed from the image or alpha.
So it works on the beauty, but not the alpha channel.
I will check out Beppe's solution, maybe it gives more liberty.
In this specific scene I would like to remove the shadow catcher (maker) object to be subtracted from the alpha channel.
I know I could re-render twice, but I would try to avoid that in a 2000 frame animation.

[Hatsize7]

Hi,
please consider that the Matte/Shadow catcher option is not perfect, and has some limitations, for example if there is an emitter material in the scene.
Much better to avoid to use it, replace the Diffuse material with a Glossy material, and use the Render Layer technique instead:
http://www.aoktar.com/octane/RenderLayer.html
In this way you can obtain shadows and also reflections on the ground.
ciao Beppe

This solution worked, thank you bepeg4d!