IOR values... Is there a "simple" approach for realism?

[zach_ryder]

Is there a straight forward approach for understanding IOR values? I watched a video on this and the guys was explaining that metals should be around 7-15 and mirorrs much higher. But with vray default values of metals, it's closer to like 1.35 for gold and other values for other metals. and one website I saw said gold is 0.45. Why is there so much information contradicting each other? or do i just not understand how it works?

[dimitar_panayotov]

Hi, in this Blog post, you can read more about Metals. There are some examples as well.

[seandunderdale]

While probably still relevant in many ways, the info about metalness and IOR is out of date, since IOR is disabled when metalness is enabled...at least it is in Maya, I cant say if its the same in MAX.

[dimitar_panayotov]

Yes, you are correct. The information in the blog post is relevant for older versions. Similar to what it is in Maya, IOR will be greyed out, when Metalness is set to 1. This change is registered under VMAX-13466 in our system.
Even though, IOR is active now, it does not affect the result when metalness is set to 1.

[zach_ryder]

so for things like paints (walls, cabinets, etc). Is it suggested to stick with 1.6 as the vray default? I don't really understand the refractiveindexinfo website that well.

[seandunderdale]

Heres a link to IOR info

https://pixelandpoly.com/ior.html

Also here's an image..

If you have budget, you can sign up to vray scans, and make shaders that match the values. Ive done that with plastics and carpaint. Once I have rebuilt shaders that match 95% in different lighting, and all angles, then I can build out a library from there using those as a base for calibration.

[zach_ryder]

thanks that helps alot. Yes I think I should look into Vray scans that sounds like a good solution for saving some time from doing all of this from scratch. Thanks for the help

[zach_ryder]

So to my understanding, IOR is pointless when metalness is set to 1. So does cosmos materials just show the default values for the purpose of showing you what is should be if the metalness is not set to 1? Because If you take away all metalness, it seems like you would have to bump up the IOR much higher to get a "metal" material.

[seandunderdale]

IOR greying out when metalness is on, is a new-ish feature. Before, you did have to input IOR values for metalness of around 1.01-1.2 sort of thing. Pre metalness, you did have to use much higher IOR values to get "normal" vray reflection to look like metal. Personally I would use IOR - 5.0-8.0 for a chrome, or something like that. I did see efforts from some to dial in accurate IOR's manually, but eyeballing it tended to work ok.

Dont forget, you might also have access to the vray material presets. We have them in Maya, so I assume theyre in MAX too? These seem to have the latest IOR colour / value inputs, so itll get you started.

[zach_ryder]

Interesting. So really IOR isn't used for metals instead the engine take into account the diffuse and reflection color?

[seandunderdale]

Yes, but internally those RGB colours are driving a fresnel effect. If you look at the swatch as you move to extremes, there is a lot of falloff happening when you move sliders around.