3d coat how to input measured IOR values?

Super_nova

so I am using 3d coat for a material study and i need to use measured IOR levels but I don't know how to input those values, for example I have a gold coin and the measured value for gold is 0.470 . Do I input 47% into the metelness value? that dos not seem right what do i do?

Alex_J

Metalness is not the same thing as Index of Refraction.

Metalness is usually off or on. White or black. 0 or 1. That is because most surfaces either reflect light like a metal, or not.

This is one of the best, artist friendly introductions I've read:

https://marmoset.co/posts/physically-based-rendering-and-you-can-too/

I can't answer your question directly. I didn't think you'd need to use IOR with gold as it is opaque. I thought IOR is dealing with refracted light. Like what happens when light passes through water. The rays get bent, and the index then is something to do with how much so. That's just my very simple layperson understanding, so don't take it as scientific statement.  I think you'll find your answer in that tutorial though. Or at least a better idea.

Eric Chadwick

IOR is used for both reflection and refraction.

For metals, you use either Metalness 100%, or you use a high IOR value (whichever your material supports. metalness is generally better). High values for reflection IOR increase the amount of reflection on surfaces that face the camera.

Super_nova

my question is more about how I input "measured IOR values" into the software then the proper methodology gold  was just an example of a value

ZacD

Wouldn't measured IOR values be an average of the reflectivity of all wave lengths of visible light? Shouldn't the specular color (included in the base color texture for metalness) be all you need? Or would you need to turn down the metalness from 1 to .9 or something to simulate that?  

Super_nova

I just got the bit About base color and finally understood it's mening

Eric Chadwick

Does 3D Coat have an adjustable IOR in the PBR material? I couldn't find any good help docs.

poopipe

Sebastian legarde published the maths for converting measured ior to colour values a few years ago  (can't remember if it's linear or sRGB) 

Google that and do the conversions. 

Oh,  and it's either metal or it isn't. Gray values are a fudge for when you don't have enough resolution and need to average over an area - not a way to correctly represent car paint etc. 

There are exotics that don't fit the basic system but with those you need to use a different Shader than the standard lambert/ggx

Eric Chadwick

What about dusty metal mister poopypants? Huh? Huh?? 

poopipe

That's neatly covered by the "average over an area" fudge. 

Same principle as roughness 

Eric Chadwick

Fudge.

Shrike

3D coat is really not the place to make material studies, try use some render engine or a different 3D package

Edit: I am also a bit confused with metalness, only recently started playing more with it, but generally not a big fan - Am I understanding this right in that there is no way of controlling reflection intensity in metalness? Does it have to be linked to diffuse brightness? There seems to be no equivalent to IOR / Spec intensity or how do I set up my shader? Its all one brightness and then just roughness variance?

The offline renderers I usually use, use specular maps in combination with IOR even (as ofc IOR is per material and not fit for UVd meshes)

Eric Chadwick

Yeah, albedo color is used to store reflection intensity/hue when metalness is 100%. It's one of the optimizations of metalness-roughness to reduce memory cost.

poopipe

 Yes.. basecolor is masked into the specular channel by  the metallic map and the albedo is made black - the colour values in the base colour map for metals are analogous to IOR 

The maths work out fine ( in spec/gloss you should have a black albedo for metals) but you tend to have more issues with texture resolution and compression than the spec/gloss approach - usually  leading to haloing where metal/dielectric bits meet up. 

Some (crappy)  implementations of metal/rough don't allow for variance in dielectric reflectance which makes it difficult to get decent representations of surfaces like stone and wood and makes it impossible to occlude specular highlights.