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View Full Version : Gooey eye effect. Anyone know how?


psil
08-26-2002, 06:43 PM
If you look at these renders (not mine) http://www.cgtalk.com/showthread.php?s=&threadid=10441
you'll notice a nice specular/reflective rim along where the eyeball meets the bottom eyelid. It's a nice realistic detail that looks like a small well of tear fluid held in place by surface tension. I've seen it in other work too, e.g. the FF close-ups.

I'm guessing it's a texture trick, but could be a modelling or lighting thing ?

Does anyone know how to do it ?

Tumerboy
08-26-2002, 07:01 PM
one way is to just make a little rim of polys that you texture like water.

Those polys would be part of the lid, not the eye, but may extend into the eye a little ways. . .

Dunno if that's how that person did it, but that's how I've seen it done before.

psil
08-26-2002, 08:13 PM
Cheers, Tumerboy (what a knowledgeable fellow you are!). I'll try it like that

Originally posted by Tumerboy
Those polys would be part of the lid, not the eye, but may extend into the eye a little ways. . .

i.e. the polys would overlap/intersect ?

Tumerboy
08-27-2002, 08:42 AM
yup, basically, you could just put a row of polys in that go straight through the eye, and the eye lid. just texture it like water.

leigh
08-27-2002, 10:26 AM
In my opinion, the guy who did those renders went a little overboard with his shininess and reflection, but he has indeed got the right idea :)

As Tumerboy has suggested, a bit of extra modelling is in order - however, I would recommend actually modelling a layer that covers the entire eyeball, and tearduct, and texturing that as liquid - because the eyeball is always coated in a layer of liquid, as well as the tearduct ;)
Remember though, that if you use this method, then you need to texture the eyeball itelf to be not as reflective as the liquid layer - an eyeball that is not wet is not particularly shiny. It only appears that way because of the water coating it.

Alternatively, you could use a BRDF shader - but I don't think that the result would be as realistic, seeing as BRDF shaders usually work with specular reflections and not true reflections.

psil
08-27-2002, 01:11 PM
cheers guys.

Atm I have separate transparent geometry for the cornea covering the eyeball, but not covering the tearduct. Leigh, do you mean more geometry on top of that?

That's why I wondered about the intersecting polys that Tumerboy suggests - in case all this intersecting transparent geometry gives odd reflections &refractions (I s'pose I should just try it..).

Anyhoo looks like a modeling job with no quick surfacing dodge

thx again.

Tumerboy
08-27-2002, 04:13 PM
ya that's what she's talking about.

Take the eye you've got right now, add another layer on top of that eye, that is barely separate from it, i.e. only barely bigger than the eye ball itself. Give this the water type texture, and make this layer shiny. Take the specularity down on the eyeball so that it's barely shiny, and maybe quite matte.

Then as either a separate piece, or as part of that clear layer, make the little well of tears at the bottom of the eye.

Hope that all makes sense.
cuz I just woke up :P

psil
08-27-2002, 06:31 PM
Originally posted by Tumerboy
ya that's what she's talking about.

Take the eye you've got right now, add another layer on top of that eye, that is barely separate from it, i.e. only barely bigger than the eye ball itself. Give this the water type texture, and make this layer shiny. Take the specularity down on the eyeball so that it's barely shiny, and maybe quite matte.


Aaah that would be the cornea I mentioned - I already gots me one :) I thought she meant another transparent/reflective/refractive layer on top of that.

Had a quick try with extending a rim of 'water' polys from lower eyelid - doesn't look half bad. tweak.render.tweak.render...

Tumerboy
08-27-2002, 06:53 PM
No. . . that IS what we're talking about. You've got your eye, with cornea, that's the eyeball, then Make an entirely new layer of polies, barely above the eye surface (including the cornea) then make all of your eye surfaces, dull. And make the new layer shiney and watery

psil
08-27-2002, 08:18 PM
Oh, I see:eek:

just as a matter of interest, what for? Unless the cornea and watery layers are any further apart than the eqivalent of a single pixel in rendered output (i.e. fantastically close-up, in which case the intersecting tear well geometry would become very obvious), wouldn't that entail calculating half the net refraction and transparency twice to get the same picture?

I can see the need for 1 matte/opaque layer behind another refractive/transparent/reflective. But two of the latter, so close together..?

Tumerboy
08-27-2002, 08:39 PM
I'm only talking about one layer, there's the eyeball dull layer, and the water shiny layer.

I think what you're calling the cornea is what I'm calling the watery layer.

The cornea on an eyeball is the same material as the sclara (the white part) and in terms of 3d that those would both be the dull eyeball layer.

Then on top of that would be the watery shiny layer.

sorry for the confusion

Gentle Fury
08-30-2002, 04:29 AM
This is why when you texture you make a color map a bump map, and of course the all important spec map!! (you may want to build seperate maps for other attributes too, but these are the important ones). Using little gradient dots in the spec where you want a shiny, wet look works wonders :) Also make sure where you need it to be a moisture area you make it less bumpy, since ears and lips generally tend to be smooth from always being moist. I agree with leigh though, those images are gorgeous, but it kinda looks like they went a lil too far.......kinda looks like they are having a moisture problem ;) but the skin tex is gorgeous!

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