PNG Alpha output on single object?

[pkanis]

Our company uses Keyshot to render championship rings and I noticed that adding ground plane/backdrop underneath or behind the object gives us a more realistic image which is what we want.  See the two examples (not great comparison but it's what I have available atm) and notice the difference.  The one without a backdrop was rendered out in PNG alpha but the other one I can't because it wants to render everything.  I prefer the one with the backdrop.  Is there a way to just render the ring without the backdrop or ground plane in PNG alpha format?
Thank you!

[TGS808]

Turn off all ground planes and or backdrops. Uncheck "ground shadows" in the Environment tab. Render with alpha transparency turned on. That will give you only the ring on a transparent background.

[pkanis]

Thank you.  Will I still get the look on the ring?  Does the scene assume the background/ground plane is still there?

[TGS808]

Ahhhh.... I see. You liked the look of the ground plane reflecting on to the ring. Forget the ground plane. The ring is going to reflect whatever HDR environment you have wrapped around it. Get a good HDR image (there are some stock ones in KS), add it as your environment and you'll get nice, more realistic reflections on the ring. You'll be able to render it that way with the alpha transparency.

[RRIS]

You should experiment with render layers, especially the shadow and clown passes. The clown pass will give each individual object in your render a unique color, which will make it easy to crop out a background plane for example. If you have the shadows in a separate pass, you could remove the background plane, while retaining the shadow information on it (but don't hold me to this, I haven't used render layers in Keyshot a lot, because it can be a bit fickle on how it behaves with certain materials and GPU rendering). Will Gibbons just released a video on render layers on youtube, so make sure to look that up to get you started.

[INNEO_MWo]

Just put all the ring parts on a render layer and you'll get the image without the ground shadow.

[TGS808]

Just put all the ring parts on a render layer and you'll get the image without the ground shadow.

I really should have thought of that. Great, and simple solution, Marco!