shadowmatte - set object to cast shadows, but not on itself

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Hi,

Does anyone know how to make an object cast shadows on other objects, receive shadows from other objects BUT not receive it’s own shadow?
I would like to output a shadow AOV with the shadow from a volume on the surrounding environment, AND ONLY this shadow information, no other.

I used this topic, but could not go any further:
https://forums.odforce.net/topic/12615-shadow-catcher-material/ [forums.odforce.net]

In the end what I would like to have is a pass with:
- C = the volume with shadow from the set onto the volume
- AOV my_shadowmatte = only the shadow of the volume on the set (without the set’s self shadowing)
And I am not even sure this is possible at all

So far I can only have:

pass 1 with:
1a- C = the volume with shadow from the set onto the volume
1b- AOV my_shadowmatte = shadow of the volume on the set AND the set’s self shadow (both are mixed and therefore cannot be separately tuned in comp)

or pass 2 with:
2a- C = the volume WITHOUT the shadow from the set onto the volume
2b- AOV my_shadowmatte = shadow of the volume on the set only

I could render both passes and give them to comp, but that makes me render the volume twice

So I would like to have pass3 = 1a + 2b in one render pass only, so that I can save one volume render
Makes sense?

Is there a way in the shader to know what object occludes the light, I could use that in the shader maybe?

thanks!

Attachments:
volume_shadowmatte.hiplc (1.0 MB)

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I'm not quite sure what you are after. What renderer? There is a light mask on any object, sort of light-linker…
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Hi
thanks for looking into this
I am using Mantra, on Houdini 17.5.391
Regarding light mask they both need the same light to have the same shadow
It's just that in the shadowmatte aov I want the shadow from the volume only, and not the shadow from the catcher (the environment geometry) BUT I still want the shadow from the environement on the volume in the beauty
Not sure this explanation makes it clearer, let me know
thanks!
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I´ve been looking for this too. Vray has this option where you can have an object create a pass where it receives shadows, but no its self shadows. Don´t know if Mantra has a material that can do that.
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For mantra should work a “shadow mask” on light, like


* ^yourobject

I think.
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I tried above, not luck, but take a look here. Maybe it can move You somewhere.
https://forums.odforce.net/topic/12615-shadow-catcher-material/ [forums.odforce.net]
Edited by Bretislav Kaspar - Oct. 22, 2019 09:14:02
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