Your FAQ section uses an Add shader where I think it should use a Mix shader. My understanding is that the shaders reflect light that is scattered diffusely, light that is reflected coherently (specular reflection like a mirror) from a smooth glossy surface, and light that is refracted and transmitted through a transparent material. The mix shader uses the factor to determine how much of each of the three occurs, dividing the incoming light the three ways. An Add shader would have the same light reflecting and refracting, creating more light out than is coming in. This could be used for effect but won't be consistent with the actual physics.
Here's the general case:
The value node is just there to show that the roughness factor that determines whether light reflects coherently or diffusely is a single physical property of the material and should have the same value in the two nodes. The key point here is that light will either refract through the transparent surface OR reflect off of it, so the more you reflect off with the glossy node the less makes it through to the eyeball below, so a high gloss will produce a dim grey eye underneath. So if you want both gloss and a white eye the solution is to crank up the light rather than crank up the gloss.
For they eye, we can simplify the exterior surface to only reflecting and refracting light, simplifying the nodes to:
- The eye on the right has a high gloss setting so little light makes it to the underlying surface
- TooGlossy.png (39.62 KiB) Viewed 5986 times
- With a factor of 0.1
- LowerGloss.png (38.96 KiB) Viewed 5986 times
- Using a Fresnel node for the gloss versus transmit factor. Light that hits at small angles is more likely to reflect than refract.
- Fresnel.png (40.68 KiB) Viewed 5986 times
For the inner surface if we ignore reflection and refraction just model diffuse reflection the nodes for the inner surface are simplified to:
Let's see if someone corrects me before altering the FAQ.