Procedural iris texture

Create an algorithm that generates a good enough iris texture for usage in the Eye model.
The Iris texture should :
- Be of acceptable size to render correctly in the Eye model (half sphere)
- Provide enough detail to be acceptable / visually interesting
- Have an easily parametrized iris color
- Ideally have several components of a real iris (two layers and some "holes")
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The ImageProcessor tool is probably the best to be used to develop this algorithm.

Start by inspecting the Eye model and the ImageProcessor tool to understand how textures are represented and applied. Develop and evaluate a parametrized iris texture that renders at an acceptable size, has visible detail, and includes the requested color, layers, and holes.

Written by the indexing model from the issue text.