Author Topic: Trying to understand Fresnel IOR  (Read 1421 times)

2018-10-19, 07:33:06

monitorhero

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Hello guys,

since I am new to Corona I would like to ask about a few things:

https://coronarenderer.freshdesk.com/support/solutions/articles/5000515622-how-to-set-up-realistic-glass-metal-materials

Here for a chrome material an IOR value of 32 is suggested. I never saw IOR values like this. Isn't that physically inaccurate? Where do I get the correct values from?

Also if I have a plastic I use an IOR of 1.52. Do I still need to set the reflection level to 1? Or how does the Reflection Level correspond to the Fresnel IOR?

On this site https://pixelandpoly.com/ior.html an IOR value for Chromium is 2.970


Thanks in advance

monitorhero
« Last Edit: 2018-10-19, 07:41:52 by monitorhero »

2018-10-19, 11:07:38
Reply #1

dj_buckley

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As far as I understand it, for the vast majority of non-metals you can leave reflection at 1 and IOR at 1.52.

For metals it's a bit different - the way I work with metals is Diffuse Level set to 0, Siger Shaders Complex Fresnel in the Reflection Colour Slot as a starting point, Corona Color in the IOR slot set to 99999, 99999, 99999 for RGB - which effectively disables the IOR, at this point I'll fire up Interactive Render and tweak the colour of the metal using the settings available in Complex Fresnel and then the blurriness of reflections using the Reflection Gloss value until it looks right to me and/or my reference.

Of course this is only for 'pure' untouched materials.  If I want to add a bit of realism then I also add some Gloss Maps into the mix and or Layered Materials.

Whether I'm doing things right or wrong, I don't particularly care, as long as it looks good/correct to me and the people paying for it.

2018-10-19, 13:57:02
Reply #2

monitorhero

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As far as I understand it, for the vast majority of non-metals you can leave reflection at 1 and IOR at 1.52.

For metals it's a bit different - the way I work with metals is Diffuse Level set to 0, Siger Shaders Complex Fresnel in the Reflection Colour Slot as a starting point, Corona Color in the IOR slot set to 99999, 99999, 99999 for RGB - which effectively disables the IOR, at this point I'll fire up Interactive Render and tweak the colour of the metal using the settings available in Complex Fresnel and then the blurriness of reflections using the Reflection Gloss value until it looks right to me and/or my reference.

Of course this is only for 'pure' untouched materials.  If I want to add a bit of realism then I also add some Gloss Maps into the mix and or Layered Materials.

Whether I'm doing things right or wrong, I don't particularly care, as long as it looks good/correct to me and the people paying for it.

Thanks buckley, that's how I have been doing it too. I was just wondering about the workflow if I don't use ComplexFresnel. Why do they use high values like 25-32 and where do they come from? Trying to understand the math behind it.