Render transparent (glass) object without background, but with reflections?

Good day,

I want to render an object made from delicate glass. This will later be a PNG used in Unity as game asset - and it has to be transparent (Say a Christmas tree ball - with prebaked light on it)

First thing I did was to apply glass/transparent shader, but render does not look like glass because there is no background and it has nothing to reflect.
I’ve tried adding another, smaller sphere inside which should be a perfect mirror (Glossy set to Sharp with 0 roughness) - while unchecking Camera Ray Visibility in hope that it will cause some light bouncing inside the main sphere without showing on render, but that didn’t work for me.

Maybe somebody here has suggestions about how to achieve this?

Why not set the background to a environment texure and turning off camera ray visibility?? (you need also to check “transparent” in the render/film panel).



I think that worked. Haven’t tried with transparent yet, but glossy objects look much much better.
Thank you!