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12-08-2014, 03:22 PM   #1
Skalman
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Arnold realistic eye specular
Ok so i've spent all day yesterday and so far all day today trying to get the realistic look of an eye. I've got 3 objects for my eye, the iris, pupil and the lens. The pupil and iris materials are done, the problem i have is getting the right specular for the lens, which seems to be really hard for me. Ive been looking through some references on google and i belive that my lens specular needs to be less reflective around the eye-white, also my specular has to decrease at darker areas. for you to get my point clearly i will provide some images


^ here we can clearly see how the sky and the bright buildings in the reflections are very reflective, while the darker areas (the photographer and the darker buildings). Also the eye-white isnt as reflective as the lens, should i create a map for the eye-white and the lens over the iris?

guys im really confused right now, and i havent found any tutorials on eye shader for arnold materials ...




None of the changeable attributes under specular doesn't do the trick. im clueless right now





this eye problem has taken me to the point of where im starting to doubt that there is a difference between specular and reflection
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Last edited by Skalman; 12-08-2014 at 03:24 PM.
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12-08-2014, 04:59 PM   #2
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Looking at a tutorial for mental ray's material, the specular in the mia_material_x seems to be doing what i want. dark reflections = more transparent and the other way around. What is wrong with arnold's specular
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12-08-2014, 10:11 PM   #3
Gen
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I don't use Arnold so I can't give you detailed shader specifics but try turning on Fresnel as a start. Right now your eye seems to have very uniformed reflectivity which isn't realistic, especially in the case of eyes. Then tighten up the specular highlights for a wet appearance.
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12-08-2014, 10:19 PM   #4
Skalman
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Thanks for the reply. been waiting all day for someone to try and solve this with me :p

Yeah ive been playing around with the fresnel, and according to solidangle (https://support.solidangle.com/display/AFMUG/Specular) fresnel should do the trick, but in my case it doesnt. i belive the refraction might have something to do with this...

Is there any way to get a good render with mixed renderers? I think i ran across someone saying that they like to render some parts of their scene with mental ray and some parts with arnold, but that seems crazy to me ... or is this a thing?

Also, i dont know why i didnt have max spec value + white map on at the moment of taking the screenshot :o
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Last edited by Skalman; 12-08-2014 at 10:21 PM.
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13-08-2014, 12:47 AM   #5
Gen
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There are IoR tables all over the net actually.

https://www.robinwood.com/Catalog/Te...IndexList.html

Cornea is near the bottom

Some more sources

http://www.pixelandpoly.com/ior.html
http://vray.info/topics/t0077.asp

About the mixing renderers, yes you could even create render layer overrides on what renderer to use.
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13-08-2014, 11:02 AM   #6
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Thanks, gen! Didnt think about changing the index of refraction actually! Ill try some more with this Arnold mat, then ill consider rendering the eye in mentalray. Do you know how id get the right reflections in mentalray? Since all Arnold materials Will be looking weird in mray render
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14-08-2014, 02:40 AM   #7
Gen
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Just to clear things up, I didn't mean try to get MR or Arnold to render out a scene that's a mix of shaders belonging to the respective renderers(as you found it, that doesn't work). I meant that you could set up render layers with shaders and settings specific to a particular render and batch them out, that's just one way. Or batch out separate scenes period. Either way you're compositing the elements into a final image in another program(After Effects, Nuke etc).

Given that the eye is modeled well , I'd say the material settings are only a part of it. In the case of the cornea, we already talked about Fresnel reflections and the correct IoR. We know it's almost completely transparent, highly reflective and smooth so that should be the starting point. Another aspect would be lighting and environment. That means not just having an environment for it to reflect but also proper exposure(it's near impossible to emulate photographs without taking this into consideration). If you break down the reference image a bit and check out "why", we'll figure out the "how". You'll see that the environment is high contrast with a large bright spot, that coupled with the child's dark eye color providing even more contrast makes the reflection really pop. The cityscape image is not similar to these conditions so you probably won't get comparable results even with Fresnel reflections. It looks kind of flat too(hopefully it's HDR).

Check this out, the reflection is prominent because the creator Chris Jones used a high contrast IBL with an isolated bright spot.

Eye Piece - YouTube

And just the eyeball. Alright I'm done ranting
Eyeball - YouTube
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Last edited by Gen; 14-08-2014 at 02:44 AM. Reason: Stuck in video embed hell again lol; Alright fixed!
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20-08-2014, 08:44 PM   #8
Skalman
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Thanks alot, Gen !!! Yeah I'm trying to learn this specular now, following https://support.solidangle.com/display/AFMUG/Specular , hopefully ill get the "aha" thought that reveals the problem for me. Besides, i saw that eye video you linked in the new 3d world magazine :p really an awesome work, so much inspiration... Ill get back to the eye soon again. once again thanks alot for all your help. i see some paths more clearly now because of you
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