Corona Shadow Catcher Material - Reflection question

[redlad]

Hello,

I have a question about the Corona Shadow Catcher Material. I want to render just the reflection, but in the alpha I am getting the shadow.

Is there a way of just getting the alpha of just the reflection? Like the Matte/Shadow/Reflection shader in Mental ray.

Thank you!

[maru]

Hi, sorry for the late reply. It is hard to understand your question without any kind of examples of what you would like to achieve. Could you explain it further and/or post some example images?

[Paul Jones]

I guess you are after a matte shader that will show reflection and not shadows.
Mr has the option to receive Shadows, AO, Reflections all combined or individual.

Attached render shows reflection checked and shadows unchecked.

Not sure of a work around, but I used this a lot for a series of product renders, very handy.

[Paul Jones]

Basically it should just be a shadow catcher material, but a shadow/reflection/gi/ao catcher material

[GestaltDesign]

I had similar issues, except I wanted a pure shadow catcher without the GI input of the backplate for a product shot.
I found the solution was to use the Rayswitch material and  the run shadow catcher through it to deactivate individual passes :)

[maru]

Possible way of rendering only the alpha of the reflection: set "enviro/backplate" color of the shadowcatcher to pure black.

[egoroshe]

This method does not work with glossiness less 1. What to do in this situation?

[maru]

Why are you saying it does not work? What is the expected behavior here?