A physically based model of ice

Animations of freezing and ice formation are becoming increasingly popular in visual effects, making prominent appearances in such recent movies as X-Men 2, The Hulk, and Die Another Day. However, the methods for modeling and animating these patterns remain fairly ad-hoc. In this sketch, we present a complete physical model for simulating ice formation. Inspired by the three stages of solidification commonly known in statistical physics [Saito 1996], we model each stage explicitly, and design a novel algorithm that is well suited for visual simulation. Due to the fractal nature of ice, our algorithm scales naturally from the small crystal arms of a snowflake to the large frost on a car windshield. The algorithm also allows for natural, intuitive controls so that the user can guide the results toward a desired aesthetic effect.