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Old 06-09-2007, 02:30 PM   #1
gubar
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Default Making an eyeball - fresnell shader?

Hi,

been working on an eyeball tutorial. Going well until I hit this section:


"The eye lens shader

This shader network is also a Phong E shader. The most important element to add to the basic shader is fresnel falloff for transparency and reflection attenuation. Fresnel effects describe the way that an object at a more glancing angle is more reflective than at a facing angle. In mathematics this is derived as the dot product of the normalized incident vector (the direction the camera is looking in) and the surface normal. In Maya this value can simply be obtained from the samplerInfo utility which has a parameter called "facing ratio". I pipe this facing ratio value into the U parameter of a U direction ramp. This enables me to remap the facing ratio values in a more user controllable way to define visually how the reflection and transparency fall off."

Anyone know how you actually do this? I have checked the help files and though it explains what fresnel is in principal, it doesn't explain how to actually apply it.

thanks,

gubar.
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Old 06-09-2007, 04:04 PM   #2
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Yeah, creata smapler into node and a ramp, delete the place 2d node for the ramp, then mmb the facing ration to the ramp, then in the window conect the facing ration to the u value of the ramp. Then connect the ramp's out colour to the reflectivity of the material that your using (you can mmb the ramp in the hypoershade and drag it to the reflectivity value in the attribute editor (not the value but the actual text that says reflectivity)

Then use a white for high refelctivity and a black for none, adjut the ramp postionings and the values of the colours to suit the model.

To test it out you might want to really overcrank the values so you get a feel of what its doing

I use the sampler info node fore pretty much everything to do with specularity (which is faking the hotspots for reflections tbh) and reflectivness, theres a lot of it on my pirate model that I did, heres a link toi a larger picture, theres fresnell on the reflectivness/spec for the eyes, skin, hat.

http://features-temp.cgsociety.org/g...2785_large.jpg

linkey to it.
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Old 06-09-2007, 08:11 PM   #3
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Thanks again,

that's the info I was looking for.

cheers,

gubar.
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Old 09-09-2007, 02:11 PM   #4
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Hi,

still working on my eye. Here is my shading network for the outer eye sphere so far, with the fresnel effect in place on the eye. Any comment on the ramp in particular appreciated.

I am wondering though, if there is a way to fake an environment in maya to test render? Rather than modelling or downloading an environment, just so I can test my reflections.

cheers,

gubar.
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Old 09-09-2007, 05:53 PM   #5
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Cant really comment on the ramp, its just a ramp to me.

your best off playing with the settings yourself.

I would make a plane add a pic to it for some reflections
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Old 12-09-2007, 07:38 PM   #6
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Ok, here's what I've got, though it's not having the desired effect. It seems to control the overall reflectivity, and to a small degree reflectivity away from the centre - but not in terms of pitching the reflectivity more towards the glancing, rather than facing, angle.

Have I set it up correctly?

thanks,

gubar.
Edit: Looking at my network I notice that, when I drag and drop the ramp to the reflectivity in the atribute editor, it attatches the alpha out to the reflectivity; if I open up the connections, I have the option of connecting the out colour to the reflected colour, but not the reflectivity itself.
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Last edited by gubar : 13-09-2007 at 07:10 AM.
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