In this tutorial, I’m going to show you a pretty cool technique to create a detailed eye, more specifically the iris. This is a rather long tutorial as I cover the entire workflow including the creation of texture maps for rendering.
When it comes to setting up an eye for a render there are plenty of ways of doing so. It depends on the restrictions you have on the rendered you use, whether is a real-time engine or not, etc. In the case of this tutorial, I set up a simple eye with 4 pieces in Marmoset to keep things simple.
Here is the full setup in case you want to use it as a reference to set up your own eyes:
I created a semi-sphere for the sclera and then duplicated it to create the cornea (the shiny part of the eye with the distortion lens around the iris). For the Iris I re-created a simplified version of the cylinder I used in the tutorial and for the pupil a simple flat circle plane:
Aside from the textures I created in ZBrush for the iris, I also created a texture for the sclera with a mask for the iris. Basically a square image in photoshop with a gradient from white to pink and a circular area as a mask to be able to see the iris object inside the eye. The setup is super simple, I just created a new Alpha channel in Photoshop and added the mask in there and saved the image:
In Marmoset, I applied a shader to the sclera object and drag the saved sclera texture into the Albedo texture slot and at the bottom of the shader enabled Transparency to complete the effect:
The rest of the process is just to asign other materials like a transparent shiny one to the cornea and a dark and rough one for the pupil so it has no reflection. The material for the iris is also super simple since we already have the textures we need (from ZBrush) to produce the convincing effect:
So when you put all the pieces together with the materials you should have something like this:
There are obviously a couple of extra settings that you can teak but they will be different between renderers. For instance in Marmoset, you can click on the 'render settings' icon and then enable the Ray Tracing option so that you get the nice refraction around the lens which distorts the iris depending on the angle you look at it
That's it. Once you have this setup you can easily update the sources for each texture and refine your eye... maybe export some albedo variations from ZBrush ;)