reflection IOR vs refraction IOR

[flipside]

In build 8.

When using a refractive material, you can't control the reflection IOR seperately from the refraction IOR. In other words, the reflection IOR is ignored from the moment you enable refraction, and the IOR of refraction is used for reflection too.

So for example I cannot create a material with refraction IOR=1.0, and reflection IOR=1.5. This means I cannot make a ior=1.0 refractive material become fresnell reflective, since the reflection ior is automatically set to 1.0, which means no reflection at all.

[Micha_cg]

reflection IOR vs refraction IOR

... is this not physical correct? I have thought the IOR is a surface border property. Or do want to get more freedom for artistic effects?

[flipside]

reflection IOR vs refraction IOR

Yes more freedom, that is why there are two IOR's in the material. In real life there is only one of course. In vray for max, the reflection IOR was added by popular demand, and there is an option to link it to the refraction IOR or not.

[joe_b]

reflection IOR vs refraction IOR

hmm, I'll have to ask Vlado about this. I made a test material with refraction IOR 1.0 and reflection IOR 1.55 and both the values were correct in their respective places. So perhaps this IOR problem occurs in the actual materials.

[joe_b]

reflection IOR vs refraction IOR

Ok I spoke with Vlado and it seems that the problem comes from the Fog Color and the way I set the materials up. Currently I create a volume shader for each refraction layer. The volume shader (fog color) overrides the ior of the refraction and reflection layers. Currently the volume shader IOR is controlled by the refraction IOR. So, I am going to change the materials so I no longer make this volume shader unless the fog color is non-white. Thus, you will be able to have the seperate IORS so long as you have a white fog color. In build 8, however, there is no way to get around this yet, sorry.