After reading several articles on creating eyes using procedural textures, I thought I would try to push the state of the art a bit. The eyeball model uses cylindrically mapped UVs to create the radial effect. All textures are either linear blends mapped along the Y (V) axis or Voronoi F1 noise scaled along the X and Y axes. I added a cloud texture warp on several of the other texture channels to mix things up a bit. The eyeball and iris use nodes to composite the final materials, the transparent outer surface uses either Z transparency with Minneart/Wardiso shaders or ray based reflection and transparency.
I must have closed the attachments window too soon. Here are the renders. The first and second images use the ray-based outer surface, the third uses Z transparency.
I made some major changes to the node layout in an attempt to make the iris material easier to customize. Aside from removing some redundant stenciling and alpha manipulation, I changed the iris color to use two color ramps, one for the main color blend and a secondary color added in alpha-over mode. I hid most of the messy details in groups to keep them out of the way. You can download the .blend files at the links below:
