I am officially at my wit's end.  I'm trying to improve my eye textures/shaders for V4 by making the iris/sclera border softer and more feathered.  I've gotten to the point where the main eye looks great, but as soon as I apply the EyeSurface (raytraced reflection/refraction with fresnel), BAM!  An atrocious dark ring around the iris that I simply cannot get rid of!  I've stripped my EyeSurface shader down to just a Refract node, and it's still there.  I've tried everything I can think of, including toying around with the Ray Bias (raising and lowering both accomplish nothing)!  I am desperate, so any advice you can offer will be most appreciated!

Poser doesn't have caustics, unfortunately.  Poser's refraction doesn't affect how an object, or more importantly a material, casts shadows.  it doesn't affect how an object, or materials, occlude ambient lighting (AO).  it doesn't affect how indirect lighting is calculated.  refraction only affects the surface shading of the material.  it doesn't really make light pass through the material.

when you have a material on an object you want to make clear and don't want to make the object invisible to raytracing or not cast shadows, you want to use transparency rather than refraction.

I would have guessed that it is a ray bias problem, except you said it isn't. Before I totally believe you, can you say what values (and specify units, please) you used?

If, for example, you tried lowering ray bias from 2 inches to .02 inches, you didn't actually go low enough. The separation between cornea and iris on the V4 eye, near the edge, is something like .001 inches.

To be sure, place something inside the eye that is glowing pink, something that we'll "see" if the refracting ray is passing through the iris/eye. Then if you see pink eye, you'll know for sure it is ray bias.

And, of course I do not mean to burst your bubble, but there are reasons I gave up on the V4 eye and made my own.

Of course, BB!  I believe I've gone as high as 0.016 and as low as 0.0006.  My usual value is around 0.003 to 0.005.  That's in inches.

Did you do the pink object inside experiment? If you see pink then it means that it is ray bias and no value works.

I seriously gave up on V4 eyes for this reason. V3 eyes took refraction just fine, but not V4.

Note: Perhaps use of the cornea bulge morph will help. 

maybe OP is using IDL.  maybe it would brighten up a tad with no IDL.

I've got three questions: is the eyesurface mat all that important?  Can we do without it?  Can we just use it instead of all the other mats?

 

Oh, and I just looked at it in hex... the sclaera and cornea are two parts of a sphere.  The eye surface seems to be a sphere that goes over the other two and it has what I'd guess was a lens structure under the other two.  Seems kinda messed up.

Well, it turns out it was a bias issue, but not with refraction or even AO.  It was the Shadow Min Bias that was causing the problem!  It's not perfect yet, since the raised minimum costs me a bit of shading around the lacrimal, but once I find the value that strikes a good balance, I think I'll finally have this thing solved!

Thanks for your ideas, folks!