I’ve had this issue before where the problem turned out to be that I was using a plane with no thickness as the glass. This time, however, the plane with no thickness looked fine and now I’ve added a thin thickness to it (smaller than a centimeter like real glass panes), it’s doing this. Anyone know how to help?
Hi,
If your IOR is correct, maybe you should check the orientation of your glass normals !
Good 
Just did. They were wrong, so I changed them so the inside face is blue and the outside face is red. Should they both be blue to whoever’s looking at them? Therefore, the outside one should be blue?
The blue faces should point one inside the room and the other outside and the red faces should face each other (like the original cube).
Maybe can you share your file ?
You had a lot of glass faces, some of which were superimposed :
Craft Room_jav.blend (1.7 MB)
If I can give you some advice, don’t do the modeling in one piece, think about the construction (walls, windows, doors, etc.)
Good
What did you change?
Most of the time when using architectural glass, we’re only interested in seeing single reflections. So I recommend using a single rectangle instead with no thickness, and setup a fake manual glass instead:
Layer Weight/Facing → Power 5.0 → Add 0.05 to Mix Shader Transparency shader and Glossy shader. Since the Transparency will vary, you will also get “fresnel like” shadows at no additional cost. The math is very similar to what a glass real fresnel would do, but you don’t have to think about backfacing faces.
If you need rough refraction in this setup, you can replace the Transparency shader with a Refraction shader but using Geometry/Incoming as the normal for it. To handle shadows, although not accounting for roughness, you can mix this Refraction with Transparency shader using Light Path/IsShadowRay, prior to mixing this with glossy at the end.
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In my file, you don’t see the difference ?
Here are all your glass faces (your object - “Plane”) :
I removed all the unnecessary ones and rebuilt the eight panes (my objects - “Plane.corr” and “Plane.corr-Glasses”) :
Hello,
Sorry, I’m confused,
In some discussions, you fight to obtain “PBR” materials …
Then in others, like here, you propose fake materials and fake object !
I would like to be able to understand your approach(es) ?
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Fight? Okay…
For PBR it’s about achieving a higher level of realism and a more correct response to the lighting in the scene.
For “faking stuff” it’s more about achieving a higher efficiency and avoiding problems. Refraction shader (also used in glass) does not allow for light transport without refractive caustics turned on, which increase noise and adds render time; for architectural glass this makes no sense. A realistic glass window may have three layers of glass, that’s up to 6 levels of reflections nobody cares about, and far too expensive unless you’re actually making a catalog for these windows and want this level of realism. For a glass railing, doing it proper would make more sense as you see the thickness and the effect of absorption (green edge) and total internal reflections, but you don’t do it to see double reflections.
Similarlly, fresnel node may be better to cheat for fake thin geometry based window glass unless you know how to deal with backfacing normals. The backface, and the light shadow calculations interacting with it, will not see the same fresnel effect as the front face, but that of looking from a dense material into a less dense material; think looking up into the sky from inside the water pool, aka Snells Window.
Two other examples where I may choose to “cheat”; using translucency instead of subsurface scattering if light transport is a requirement (think red curtains tintint the room red), something SSS can’t do. Like, at all, at this point. Last one is analyzing how a translucent surface reacts to light, like for a lamp shade, and then mimic that response in an emission shader; that turns the lamp shade into a direct light source rather than an indirect light source, producing far less noise.
You can choose to go hyper-realistic, but at the price of far longer render times. Knowing how to optimize and the options available to “cheat” I think is pretty important. Not exactly “cheating” per se, but I often resort to simply using box mapping or custom triplanar mapping as I can’t be bothered UV unwrapping.
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Hi,
So, does fight suit you !?
Maybe a little less aggressive, as you wish !
I could have let you choose: fight, defend, argue … 
Thanks for your response …
See you