Hi everyone.
I am writing to you for help regarding Keyshot rendering: I need to render in alpha an object (with its own shadows) which however is positioned on a 3D limbo.
The limbo must NOT APPEAR in the rendering and I don’t understand what the procedure is in this case.
Thank you all!
Use Ground material for 3D limbo,
You can get some cool things from bide video.
I Don, Yes in general you are right but this is not the plan. I intentionally shortened it just to show you graphically what limbo looked like. In reality the piano is much larger.
Thank you but the problem remains: what is the procedure to then render only the object in alpha with its shadows but without the limbo?
@max.bota Okay, since scaling the environment and using a ground material aren’t viable options, try using the Occlusion Texture to create a ground shadow pass. See video.
Use a circular gradiant in opacity input to blur out the edges of your ground plane
I don’t quite understand why you’re using the limbo at all if you don’t want it in the render.
Maybe it’s worth looking for a similar effect without using it?
Not sure why Max wants it but I can imagine the limbo is used to reflect light at the back of the object as well. That’s why I often have some kind of background so the lighht stays within the scene instead of getting lost in space 
It’s exactly for this reason, Oscar, without the limbo, the effect I get is very different. So it must be present in the scene but then in the render I would like to see only the shadows generated without the limbo. But I haven’t figured out how to do it yet.
Use a raymask node into opacity of your ground material and uncheck visible in camera.
It complicates things if you want shadow. This works if you are using environment shadows, but if you are using shadow catcher that make sure your shadow catcher is Slightly above what you want to reflect in the background. You never want completely coplanar surfaces.
You were very kind, Don. I’ll do a test now.
Thanks so much!
I’ll try this too…Thank you so much Andy!
