Invisible to camera but obscuring everything hidden by this object.

[Bornix]

Hi,

I have two objects.

I would like one object to be invisible to the camera, casting a shadow and reflections but at the same time obscuring everything hidden behind it so that the alpha is transparent ( there should be a background in place of the object).
All in all, something like a Boolean operation, I cut one object with another but it needs all the shadows and reflections.

Any ideas how to do this?

[RecentSpacesSam]

Have you tried Corona ShadowCatcherMtl and setting the Alpha mode to "For Compositing"?

[Bornix]

Technically, it works. Practically in a scene I have several shadowcatcher illuminators that illuminate my object with a schadowcatcher. Maybe I will change the scene.


I found an intermediate solution that works in my case. Double Sided material, where one is transparent.

[Tom]

Maybe you could also achieve this by using a Camera Map modifier in conjunction with a CoronaRaySwitchMtl.
The first one to put the background instead of the object itself, and the latter to replace its reflection.

[maru]

I think I have managed to get what you need. :)
Create a Corona Legacy Material (because it's easier to get non-physical properties with it, such as lack of reflections).
Set its refraction to 1 and IOR to 1. That should make it "invisible".
Under advanced options set alpha to "always black".
Then plug a Corona Rayswtich Map into this material's refraction color and make it GI - black, reflect - black, refract - white, direct - white.

It should also work with the Corona Physical Mtl somehow, but I haven't tried it.