Lowering opacity on glass material makes all refraction effects disappear

[Fredrik Averpil]

Hi,

If you create a refractive materal and just lower the opacity, you can see how the material preview (swatch) pops and all refraction effects will not show at all during render.
Has anyone experienced this behaviour and is this really supposed to happen?

Bottom line/question: is it not possible to combine a refractive material with opacity?

Edit: I'm on nightly build 23166.

[t.petrov]

Hi,

If you create a refractive materal and just lower the opacity, you can see how the material preview (swatch) pops and all refraction effects will not show at all during render.
Has anyone experienced this behaviour and is this really supposed to happen?

Yes, this is by design. The problem is that it is not pretty clear what needs to happen in this case (handling/calculating IORs is a bit problematic).

Bottom line/question: is it not possible to combine a refractive material with opacity?

Edit: I'm on nightly build 23166.

You can try to use blend materials to workaround the problem.

[Fredrik Averpil]

I see.

It seems to work fine when using a blend material, like you suggested, (glass material as base and then a standard material with opacity 0 - making it invisible - as coat and then blending towards the transparent/coat material). However, why not implement exactly this type of behavior when changing the opacity directly on a refractive material?

At least, I think that this behavior is what most people would expect would happen when changing the opacity on a refractive material. I mean, it's better to have that than having the refraction completely pop away.
But I don't know if it's an easy feat to implement, of course.

Either way, thank you for your blend material solution!