Procedural Eye

Download the eye and Mental Ray shaders for Maya 2013 ( Maya Binary ).
Download the Maya Ascii version. 

This is an eye that I use for personal art pieces. Everything is procedural from the size and shape of the cornea to the vein textures. Normally I set the detail lower than what you see above but the detail is there if I need it.

This was inspired by Alex Alvarez's free tutorials:  http://www.thegnomonworkshop.com/store/category/167

The backgrounds / light probes are from Paul Debevec.

Rendered turntable of eye.

The file consists of:  A control node, eye geometry with history, eye shaders, eye textures, reference spheres, ibl node and camera with a lens shader.

Control Node

This is where you access and set the attributes for the eye's shape.

• char_hi_side_eye_ctrl.iris = The size of the iris. The number corresponds to the isoparm of the main spheres.
• char_hi_side_eye_ctrl.pupil = The size of the pupil.
• char_hi_side_eye_ctrl.cornea_bulge = How far the cornea bulges out from the natural curve of the eye.  10 = typical human bulge, 0 = no bulge.  Negative numbers will make the cornea concave.
• char_hi_side_eye_ctrl.iris_concave = How much does the iris scoop inwards/outwards.  10 = concave, 5 = flat, 0 = convex.

Iris and Pupil Size

Iris Convex/Concave and Cornea Bulge

Eye Geometry

If anyone is interested in the detailed steps involved in building the eye pieces, let me know and I'll do a write-up.  The basic steps are:

• make a sphere.
• detach at an isoparm.
• connect control node value to detach node.
• create a node that rides at the detach point in Z.
• parent a deformer to that rider, in our case a lattice.
• connect control node value to the deformer.
• scale the deformer based on the detached piece's radius.

Shaders

Notes on shaders and textures

• All shaders are mia_material_x, exception is the pupil which is a surface shader.
• All textures are converted to linear color space with a gamma node.
• All "noise" is fractal noise.  Fractals repeat cleanly at the uv borders so we don't see a seam, the noise node does not.

Sclera Shader

To anyone not familiar with a shader/texture network this probably looks like a mess.  It is, but it's much better than our previous versions.

Nodes in the network:

• char_hi_side_sclera_vein_noise_threshold = Tells where the veins start and stop.  White = 0% veins, Black = 100% veins.
• char_hi_side_sclera_vein_noise = The fractal that makes the shape of veins.  Set the color gain to 0 and the color offset to 1 to turn off the veins.
• char_hi_side_sclera_vein_col_ramp = The color of the veins.
• char_hi_side_sclera_combo_col_ramp = The red color and the proportion to white of the sclera.
• char_hi_side_sclera_noise = The fractal for the white of the sclera.  Set the color gain to 0 and the color offset to 1 to turn off the noise.
• char_hi_side_sclera_bright_col_ramp = The color for the companion part of the bright section of the sclera.  I have it set to bright blue.
• char_hi_side_sclera_bump = The bumpiness of the sclera.
• char_hi_side_sclera_vein_noise_bump_md = Multiplier for the vein bump.  Set it to 0 to turn it off.
• char_hi_side_sclera_bump_ramp = Tells where the bump on the sclera starts and stops.
• char_hi_side_sclera_shd = The sclera shader.

Veins On and Off

Iris Shader

 Nodes in the network:

• char_hi_side_iris_base_col_ramp = The deep, background color of the iris.
• char_hi_side_iris_noise = The fractal for the brighter, radial lines in the iris. Reduce the frequency ratio to simplify. Set the color gain to 0 and the color offset to 1 to turn off the bright lines.
• char_hi_side_iris_col_ramp = The color of the bright lines.
•  char_hi_side_iris_shd = The iris shader.

Iris Colors 

 Detailed to Simplified Eyes

Cornea Shader

Nodes in the network:

• char_hi_side_cornea_noise = A continuation of the sclera fractal into the edge of the cornea.  If you edit the sclera fractal ( char_hi_side_sclera_noise ) do the same edits to this texture.
• char_hi_side_cornea_col_ramp = A continuation of the sclera bright color into the edge of the cornea.  If you edit the sclera bright color ( char_hi_side_sclera_bright_col_ramp ) do the same edits to this texture.
• char_hi_side_cornea_trans_ramp = The transition from opaque sclera to clear cornea.
•  char_hi_side_cornea_shd = Cornea shader.

How to add it to your character

Without knowing how you rig and deform your characters, it's a little tough to give a definitive answer.  This is how we integrate the eye for our characters.

• Import the eye template.
• Rename all of the nodes to match the current character.
• Cluster: char_hi_side_sclera, char_hi_side_cornea, char_hi_side_iris an char_hi_side_pupil.
• Move and scale the cluster to the character's eye location.  Note that the eye is 1cm in diameter, so if you need your eyes to be 2.4cm ( human size ) you scale the cluster to 2.4.
• Bind the eye to an eye joint.
• Lattice the same nodes as above if you need non-spherical eyes. We make non-spherical eyes all the time.
• Deform the lattice to the desired shape.