[seghier]

when i tested the boolean with nested dielectrics i got this result



The hdri is visible only from invisible objects

https://www.dropbox.com/s/rgtkoqb7sx7e9rn/3.mxs?dl=0

[eric nixon]

Render is correct,... objects are not invisible, they are refracting the light from the hdri into the camera.

[seghier]

invisible when lights ON

[Mihai]

invisible when lights ON

Confusing what you ment by "lights" in this case. You mean when you disable the background image in the IBL lighting - it reveals that in fact the refraction map is still taken into account for this object even though it has an nd 1 material applied to it. I'm not sure this is entirely a bug because that refraction map should really be called transparency map. It's what shows after a ray goes through a transparent material, whether it's refracting or not. It problably happened before the material priority number. But I've reported it to the developers.

[seghier]

maybe it is useful ; no nested priority here
but the problem is when we use it with boolean
your other questions ; you have the scene try it