Odd refraction behaviour

[fixeighted]

Not really sure if this is an issue or just something that will just happen due to some limitation or oversight on my behalf. Seems really weird though.

I have a dome light/hdri.
A vertical and a horizontal plane, with a non reflective glass material.
Some spheres to see what it going on in front and behind.

What happens is that the non reflective glass is reflective, so it reflects the environment and objects.
Weirdly there is also a reflection of the full dome on top of that.
Then it does weirder stuff based on angle, where the dome reflection seems to be treated as subtraction, making
the material transparent, with ior controlling how much that happens, although the rest is still reflective.

Here's the scene. Just substitute the hdri for whatever. I'm very curious as to why this should occur.
https://www.dropbox.com/s/p6haky3ajc...CTION.max?dl=0

[^Lele^]

Shell your thin planes.

[fixeighted]

Oh yeah I know that Lele; it's not a case of not knowing that or not having 'fixed' it

I'm just curious as to why it happens is all. How refraction is suddenly seen as reflection and why the
reflection, although unexpected, is at once correct, yet still has an extra reflection of the full hdr dome in it.
And why, when viewed from a slightly different direction, that full dome reflection is suddenly a subtractive refraction.

[^Lele^]

It's all refraction.
Of the bad kind, as the ray never exits, nor gets absorbed.
It simply isn't meant to work this way.

[fixeighted]

Hmm...I guessed it was something about rays

Anyway, the reason I asked is that it is in relation to the post about the 1 sided mirror glass.
I only noticed this behaviour when I was making it work.
I used a two sided material and this odd behaviour exists - but I can fix it by ticking the 'multiply by front diffuse' box

Bear in mind that this behaviour in and of itself doesn't distress me in the least - it's just curiosity and a need to understand

[^Lele^]

Eh, it finds nothing after the first interface, ending in the environment.

[fixeighted]

Cool...kinda cryptic....you should be a crossword compiler