Certain real-world objects remain difficult to realistically model and render. The human iris falls into this category.

In the creation of artificial eyes, ocularists use a clearly defined, artistic technique for creating, in material form, an artificial eye. First, a base color is selected for the eye (blue, green, or brown). Next, 30 to 70 individual semitransparent layers are painted, each separated by a clear coat. The ocularist uses a palette of less than ten colors. The result is a realistic-looking prosthetic eye.

The technique described in this paper mimics this approach in three steps: creation of the three-dimensional (3D) geometry, iris color selection, and rendering. Constructive solid geometry (CSG) could have been used to describe the geometry of the eye. However, since many renderers do not support this technique, an alternative technique called frustums of right circular cones was selected instead. These cones are layered on top of one another. Each layer has a semitransparent texture associated with it. A base color is selected, and the overlays are applied. For final rendering, ray tracing is used.

This procedure offers many advantages. For one, it allows a user, other than the ocularist, the ability to quickly model and render a realistic looking eye. For the ocularist, it supports the layering of a prosthetic eye before material creation. This results in a customer being able to see what the eye will look like before it is created. The examples shown in the paper are quite impressive.

The authors have clearly thought out a process, where specialized hardware and software is not needed, to create and render irises. This technique could be a tool for ocularists, on one end of the spectrum, and for the entertainment industry, on the other.