Trying to understand Index parameter in Gloss Material.

[gordonrobb]

So are you saying for any kind of 'non-coloured' metal I should use 1? So steel, chrome etc?

Here is a shot of what I'm talking about. This is a test matrix of roughness and spec (or gloss and spec as it is exported). It goes in 25% increments up for Spec, and to the right for gloss. Just using it to get the adjustments for the images right in Octane.

This image is just using the textures outputted from Quixel. I think it looks good so far.

If I add an IOR of 2.5 (which I think is what steel is) it looks like this - naff.

So are you saying that unless the metal has colour, the index isn't work worrying about? And if it does, it's better to use the falloff method? If so, why do we have the IOR value

[fatrobotsneedlove]

IOR values in Octane don't have anything to do with real world IOR values. You have to eyeball it.

[grimm]

Yep, exactly, you should up it to about 6.

[Refracty]

Just crank the ior up to 7 or 8 and add some roughness. Use a high specular (white for chrome) and a colored specular if you want to create a copper material.
Crank down your diffuse or albedo a bit (you can also use the gamma settings of the texture). Add a bit of colored diffuse for copper.
Thats it.

[gordonrobb]

Thanks Refracty. When you say 'crank index up to 7 or 8' I don't understand. Isn't it meant to be an accurate number (ie 2.5 for steel) rather than cranking it up till it looks right. That's what I'm stuck with. I can tweak it till I like it, but I was thinking there was a more accurate way

[Refracty]

I guess the numbers are not physical correct in this case.

[kokozaurs]

Most metals usually have no diffuse at all so to get better results you should set the diffuse to black instead of white.

[gordonrobb]

I'm not setting the diffuse to white. It is pretty much black.

[gordonrobb]

So can I go back to one of my original points and get an answer from one of the quixel guys. What is the Index actually effecting. Is it the specular, roughness, or diffuse (or all of them) and if so how (what is it actually changing?)