Transparent glass, but keeps highlights and shadows for overlaying

[gayle_piraino]

Thank you for taking the time to look,
I'm trying to create a plexiglass box that allows for the "clear" bits to actually remain clear instead of filling in with grey while keeping the shadows and highlights
I'd like to be able to overlay the .PNG onto other images in other layout software so that the background can show through.
Attached are not my renders, but illustrates my meaning, where the .png allows the background to show through.
I've read around that maybe I should be able to do this with the Affects channel, but I'm not quite seeing where that is - and don't quite understand the meaning so my hand may need to held a little bit here.
Any help would be greatly appreciated - Thank you.

[iva_mancheva]

Hello gayle_piraino,

You need to set the Refraction Affect Channels option of the material to "All Channels":

This option will enable the transparency of the material for all render channels, Alpha included, so that the background image you add in post or in VFB will show through the object.

Kind regards,
Iva