This is pretty cool, Photorealistic Models for Pupil Light Reflex and Iridal Pattern Deformation white paper, source, etc.
Photorealistic Models for Pupil Light Reflex and Iridal Pattern Deformation from Vitor Pamplona on Vimeo.
We introduce a physiologically-based model for pupil light reflex (PLR) and an image-based model for iridal pattern deformation. Our PLR model expresses the pupil diameter as a function of the environment lighting, and is described by a delay-differential equation, naturally adapting the pupil diameter even to abrupt changes in light conditions. Since the parameters of our PLR model were derived from measured data, it correctly simulates the actual behavior of the human pupil. Another contribution of our work is a model for realist deformation of the iris pattern as a function of pupil dilation and constriction. Our models produce high-fidelity appearance effects and can be used to produce real-time predictive animations of the pupil and iris under variable lighting conditions. We assess the predictability and quality of our simulations through comparisons of modeled results against measured data derived from experiments also described in this work. Combined, our models can bring facial animation to new photorealistic standards.
Reference: Vitor F. Pamplona, Manuel M. Oliveira and Gladimir V. G. Baranoski. Photorealistic models for pupil light reflex and iridal pattern deformation. ACM Transactions on Graphics. Volume 28, Issue 4, 2009.
Project Page: http://tinyurl.com/cr6e4j
