Attached are screenshots for the Luxus material settings for the glossy eyes in my fairy picture.
First is the standard glass material for the cornea and tear. I set the refractive index to 1.48, which is the average IOR for the human cornea. I tried it with 1.33 (water) as well. Either will work nicely, but the 1.48 matches better with the settings I will use for the sclera.
The next section pertains to the Iris, the Pupil, and the Lacrimal. I included the lacrimal in these settings because they should not have the same settings as the face. They are wetter, just as the eye surface itself, so they need more gloss. I use a standard glossy material here, with a dark gray in the Absorption Color channel. This gives a translucency to the iris and pupil. I use a dark color because the absorption channel has an inverse effect. If I used a lighter color, it would actually darken the eye. This channel is also a good place to tint your iris if you want to slightly change the color provided by the texture. You could tint the Diffuse Color, but that often leads to loss in detail of the original texture. In some cases, where the texture artist has over-colored the iris, you may want to add a tint to both channels. Just remember to choose something that counteracts the offending color. I will explain this more specifically in the next section where I talk about the sclera.
The sclera, in this particular example, was a very bright white. To tone that down and allow the specular reflections to show properly, I used a darker gray in the diffuse channel than that of the iris and lacrimal. If I had used a brighter gray, the sclera would have looked blown out, and the specular reflections would be hard to see. By darkening the sclera a bit, it gives a more natural look. The absorption color is set to a dark gray as well because there is no color tint to the sclera that looks bad. I use absorption color because our eyeballs do absorb some of the light. This keeps the eyes from looking like shiny white marbles and simulates a scattering effect. An absorption strenght of .25 allows it to penetrate just enough of the eyeball without overwhelming it.
Other textures may not be as white as this one was, so to compensate I add a slight tint to the dark gray in the absorption channel. This work well for extremely white sclera as well. In one example, the eyes needed some blue added to them to kill some of the harsh white. When I am picking an absorption color, I first choose the exact color I want (very pale blue would be something like RGB 225,238,255). Then I create the inverse by subtracting each of these values from 255. So, my resulting color would be (RGB 30,17,0), which I would then put in the absorption channel. The effect is very subtle, but looks nice and won’t kill the red veining in the eye.
I keep the bump higher than I would for skin because you can lose the effect through all the glossiness and the eyes will look too smooth and perfect.
I hope these settings will help you achieve the eyes that you want without having to resort to a geometry shell, which I tried but did not like the extra hassle of creating settings for both the Genesis figure and the shell.
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