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The Principled Shader (PS) correctly applies Fresnel all the time. Brilliant! But is it based on geometry or on normals? If I have a high-poly figure with many facets smoothly curving away from the camera, I get the correct Fresnel at the point facing the camera and the point orthogonal to the camera, and all points in between, right? What if I use that high-poly to bake a normal map for a low-poly version? The geometry won't have much of a continuum of angles, but the normals will.

I think the answer is normals -- the Shade Smooth operation is just interpolating normals and I'm certain the Fresnel is calculated correctly. Can anyone confirm how this works? Or if there is a cutoff, perhaps, where you need to have a minimum amount of geometry for the Fresnel to work with the PS?

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  • $\begingroup$ In case this question is left unanswered by a blender developer: I can't see any indication of that it only uses the geometry only. I can see indications that it uses the normal map. But I can't answer with 100% certainty. $\endgroup$ – Jackdaw Feb 12 at 17:55
  • $\begingroup$ Yup, that's where I'm coming from. Sorta kinda think I know what the answer is, but it would be nice to have a definitive answer (that might reveal some useful insights along the way). $\endgroup$ – Steve Janke Feb 13 at 14:55

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