Kyle Blaine (arcangel_zero7)

3 answers · asked · Lesson: Everything Has Fresnel · Course: Fundamentals of Blender Materials and Shading

Can a Fresnel node be plugged into Principled BSDF's "Specular" slot to use an accurate IOR?

I noticed you said a Principled BSDF's Specular slot pretty much handled the Fresnel effect, but I also see that it uses a decimal value, and "0.5 is ok for most things."

If you wanted to use an "accurate" IOR value, does plugging a Fresnel input into Specular do the trick? 

It seems to act the same way, but since the effect is so subtle, I wanted to be sure it wasn't just adding needless complexity or something. :)

  • crew

    Good question! Not quite, because that would double the Fresnel effect applied to the shader and would also not result in an accurate value. Chris Plush explains the conversion between Fresnel and specular very well here:

    • Wow thanks for sharing that exact snippet! The part that got me most was "The specular value is not just a Frenel strength slider like you might think." Busted haha.

      That's super good to know and I appreciate you clearing that up so well. I'm quickly becoming less afraid of shaders! :D

      EDIT: For anyone else who sees this, the linked video also shows a node setup for converting IOR to Specular value, and conversion values for a few common example materials. Like it was said in this course though, hovering around 0.5 seems to be the sweet spot give-or-take. :)

    • crew

       I'm quickly becoming less afraid of shaders! :D

      Woohoo! Mission accomplished 🥳