If you Google “iris,” you will find plenty of images—some useful, others not—of eyes close up. If you examine the actual iris, you will see that it is built up of what look like hundreds of tiny veinlike strands called stroma. These move out from the pupil to the outer iris (or root), with their color being dictated by minute pigment cells called melanin.
We can use this information to help compile our texture. Since the stroma appears to be built up, layer upon layer, of the tiny strands, we can replicate them by also using layers.
What we need is some basic detail to start us off, so first load the iris texture you created earlier.
Following Figure 11.26, create a layer behind the pupil and fill it with noise, but make sure ...