"Thin Shell"

[dj_buckley]

If I've got some window glass setup as 'thin shell' should the glass block light at all?  I was always under the impression it stops the objects being refractive (the equivalent of ior 1) and from casting shadows/blocking light as the light is now passing straight through and not being refracted.  Now I think my understanding is wrong.  I'm just testing an interior scene and when hiding the glass the brightness of the whole interior increases quite a lot.

It's a super basic shader.  0 diffuse, thin shell, 1 refract. 1.52 ior.

A bit more testing and leaving Thin Shell ticked but changing the IOR to 1, I get the same result as if I'd hidden the glass.  So what exactly does 'thin shell' do.  Does it simply stop light rays bending?

[romullus]

Just a random guess - does your refraction colour is fully white and its strength is at 1.0?

[dj_buckley]

Yup - as I say, it's a super basic shader.  There isn't even a refraction colour in the Physical Material.  As I say it could be working as expected.  I'm just trying to clarify.  I guess the issue with physically reducing the IOR to 1 would be the reflection strength, so assuming I don't want the 'darkening' I can get around it using RaySwitch and just set IOR to 1 in the GI slot version of the material.

[Aram Avetisyan]

This way the base layer may still have effect, this is how physical material (and probably the physical phenomenon too) works.
If you put the base layer to full white, it should be as if it was hidden. Give it a try.

[dj_buckley]

This way the base layer may still have effect, this is how physical material (and probably the physical phenomenon too) works.
If you put the base layer to full white, it should be as if it was hidden. Give it a try.

Do you mean in my Rayswitch example?

[Aram Avetisyan]

I mean in the very material (CoronaPhysicalMtl or CoronaLegacyMtl) itself:
Base level 1.0, base color white, refraction 1.0, roughness 0.0, thin shell enabled.

[dj_buckley]

I mean in the very material (CoronaPhysicalMtl or CoronaLegacyMtl) itself:
Base level 1.0, base color white, refraction 1.0, roughness 0.0, thin shell enabled.

Just tested this and it makes zero difference.  The only thing that makes a difference is the IOR.

Base Level 1, Base Colour White, Refraction 1, Roughness 0, Thin Shell, IOR 1.52 = darker scene

Base Level 0, Base Colour White, Refraction 1, Roughness 0, Thin Shell, IOR 1.52 = same as previous

Base Level 1, Base Colour White, Refraction 1, Roughness 0, Thin Shell, IOR 1.00 = brighter scene

Base Level 0, Base Colour White, Refraction 1, Roughness 0, Thin Shell, IOR 1.00 = same as previous