How to use & understand IOR textures?

[dgg_joao]

I'm not sure I fully understand how IOR texmaps are supposed to work in practice in a VRayMtl. I've read this old thread, but it's still confusing to me.

What's the proper way to use it and what does it actually represent in practice? Does it replace the IOR value of the material or does it multiply it?

I also have trouble understanding what the color of the texture itself will represent. Assume I have a VRayMtl with a texture in the reflection IOR slot. This texture could be for example a checker map or something, with black and white colors. White in the texture means what IOR for the material? And black? And what about something else in between the two colors?

[^Lele^]

Assuming full texture influence, the IoR value is taken directly from the texture color.
You can easily see how it works in the material editor, assigning a vrayColor to the refraction, setting the color to white, and playing with the RGB multiplier.

[dgg_joao]

Hi! Thanks for the quick reply.

Just to make sure I'm getting it right, I did that, and it feels like the RGB multiplier 1.0 gives a similar appearance to using an IOR 1.0, while RGB multiplier 0.0 gives a similar appearance to an IOR 100, is that correct?

Here's how my material looks like:



with multiplier 1.0:



and RGB multiplier 0.0:

[dgg_joao]

Ah, my bad. I just saw you mentioned refraction, but my question was more related to Fresnel IOR textures, I didn't make it very clear. Is it supposed to work in the same way?

[^Lele^]

Identically, yes.
IoRs below 1.0 will all look somewhat similar to values above 1.0.