Discrete Stochastic Growth Models for Two-Dimensional Shapes

Discrete models for growth of a shape from a point on a two-dimensional Cartesian grid are described. By growth is meant an accretionary process occurring at the boundary of the shape. Three types of growth models are discussed: deterministic (periodic), probabilistic (stochastic), and probabilistic mixing of deterministic processes. Each type is defined and illustrated with examples. It is shown that probabilistically mixing deterministic processes can produce smooth isotropic or elongated regions, concavities, and protrusions. The paper emphasizes empirical results; analytical studies are in progress.