I've been tinkering with Gen6 lately, and while I'm grateful that Daz brought back the built-in eye surface MAT group, I'm having an issue with my Fresnel shaders, which have always worked before.

I transmap the Cornea to fade out on its edge for smoother-looking eyes.

Whenever I apply anything involving refraction, I get an outer ring on the iris that is the color it should be, while all the rest of the iris/pupil is severely darkened.  I've tried tinkering with the Ray Bias and dialing back the Cornea Bulge morph, but nothing appears to be working.  No matter what, even if I strip the shader down to just a Refract node plugged into the Refraction channel, I get the Ring of Mystery.  Both eyes have shadow casting disabled, so that can't be the problem.

Any ideas will be greatly appreciated.  Thanks in advance!

Units: feet
Ray Bias: 0.004
IOR: 1.38
Shadow Min Bias (on all lights): 0.08

Is there something in the scene to reflect? Is light shining on anything that should be reflected? What number is your raytrace bounces set to?

花 | 美 | 花美 | 花火 
...It's a pun. 

Refract on the cornea doesn't work well in Poser because it turns dark. I'd use reflection only with transparency on the cornea.

The ring is likely the reflection (and then refradtion) of the white of the eye just adjacent. Adjust the refract bias if you think you need to use refraction :).

Because the cornea is part of the figure, and because you can't turn off/on shadows by that particular part on the figure, the refract on the cornea is going to make a shadow on the iris.

Laurie

IIRC, because of the relatively small distance between the cornea and eyeball, there is really very little refraction to be seen.  LaurieA is correct, refraction is unnecessary.  There was another thread some time ago in which the refraction node was actually broken but I don't recall if this was for PP2012 or 2014 and whether it was fixed with a service release.

Thanks for the input so far, guys!  I've already tried turning the Cornea invisible and just using the EyeReflection zone.  Still got the ring.  It's weird, because the makeshift cornea/eye-surface combos that I made out of sphere primitives for Genesis 1 worked just fine, and they presumably hugged the eyeballs just as closely.

For the moment, I'll see if I can tinker with the bias again.  Higher or lower?

It seems I should have trusted my initial instincts.  The Shadow Min Bias on my lights was the culprit!

How low did you have to end up setting it?

花 | 美 | 花美 | 花火 
...It's a pun. 

Not how low, but how high.  I raised it from 0.08 to 0.18!