Normally we use Fresnel (either from the node or layerweight) to mix between Diffuse and Gloss shaders. This works best for normal shaders, but isn't always best for non-realistic shader setups, or multi layer materials. I am working on a shader setup that uses normal shaders mixed with fresnel, but also includes toon shaders with a flat mix fac.

I want to establish a relation between Fresnel IOR and a normal flat mix so that I can derive the flat mix from the IOR. In other words, I want to take the IOR input from my node group, do some math to it, and end up with a flat mix for my toon shaders that will be about equivalent in shininess to the IOR.

I understand that "shininess" isn't a particularly precise descriptor. Is there any particular math, or just general rules of thumb I can use, or do I just need to eyeball this?

  • $\begingroup$ I would just play with the settings till stuff works. No need to do fancy math for cartoons $\endgroup$
    – 10 Replies
    Dec 7 '16 at 22:38
  • $\begingroup$ @10Replies I am, but I'm also asking because I thought it was an interesting question, and someone else may have already experimented. $\endgroup$
    – Ascalon
    Dec 7 '16 at 23:21

If you're looking to calculate the Fresnel factor by yourself, a commonly used approximation is this: https://en.wikipedia.org/wiki/Schlick's_approximation

This should give you a percentage of how much "gloss" there should be.


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