Render mask "selected" behind a refractive object after update to 5.2.3

[o-v]

Hi guys

Does anyone have an issue with rendering selected object only behind e.g. a glass (window, 1 sheet)?

Here nothing is rendered... VFB remains pitch black even log states its rendering... alpha is empty (pitch black as well)

Refl. of glas material is set to "color" and refraction to "all channels"
Depth is set to 7 each. Setting depth to 20 has no effect.

The glas object is a simple box, normals are correct facing outwards, doublechecked...

Removing (deleting) the glass, all works fine...

Thank you for any hint.
Cheers

EDIT: without a render mask "selected" all works like a charm... I just need to rerender one object.. If I select the glass and the object behind it, all works as intended... I've got my render by rendering a specific object mask and composed it in PS, but I still wonder, where's my mistake in logic.

[^Lele^]

The mask is made on primary visibility.
Meaning a ray traced from the camera unto *geometry*.
It can't follow refraction, as to do so it has to trace through it first, to then find out where the mask was (i.e. secondary visibility, not primary. While simple on a glass pane, imagine if the glass had bump.).
I have no idea if it can be accomplished with LPEs instead, unfortunately.

[o-v]

Thank you very much for clarifying. Yep, the solution was select both "glass" and "the object" and render a object ID mask... and render a region to make it faster, which was the foremost goal of the exercise.

[^Lele^]

Ah, i never thought of combining the region with the masking.
Clever!