Developmental ModelingKurt Fleischer
Computer Graphics Laboratory
A challenging modeling application is biological simulation, from macroscopic simulations of the behavior of muscles, organs and joints, to microscopic simulations that model cellular and subcellular behavior. In this context we have created a new type of computer graphics modeling based on multicellular development. Using the structured modeling techniques we have developed in Barzel 1992, our developmental models combine elements of the chemical, cell lineage, and mechanical models of morphogenesis pioneered by Turing, Lindenmayer, and Odell, respectively. Developmental modeling is a cellbased modeling technique in which discrete cells are controlled by regulatory elements with conditional elements. The internal state of each cell in the model is represented by a timevarying state vector that is updated by piecewise differential equations. The differential equations are formulated as a sum of contributions from different sources, describing gene transcription, kinetics, and cell metabolism. Each term in the differential equation is multiplied by a (usually) smooth conditional expression that models regulatory processes specific to the process described by that term. The computational implementations exhibit a range of biologically relevant phenomena in two and three dimensions; through a diverse collection of simulation experiments we demonstrate phenomena such as lateral inhibition, differentiation, segment formation, size regulation, and regeneration of damaged structures. The same techniques are useful both for understanding biological mechanisms and for computer graphics modeling. The development of the underlying "modeling abstractions" advances our ability to build more powerful modeling systems. "Cellular Texture Generation," (Kurt Fleischer, David Laidlaw, Bena Currin, Alan Barr, Siggraph 1995)AbstractIn this paper we propose an approach for modeling surface details such as scales, feathers, or thorns. These types of cellular textures require a representation with more detail than computer graphics texturemapping but are inconvenient to model with handcrafted geometry.We generate patterns of geometric elements using a biologicallymotivated cellular development simulation together with a constraint to keep the cells on a surface. The surface may be defined by an implicit function, a volume dataset, or a polygonal mesh. Our simulation combines and extends previous work in developmental models and constrained particle systems.
Thesis work on Developmental SimulationThesis: "A MultipleMechanism Developmental Model for Defining SelfOrganizing Geometric Structures," Kurt Fleischer, Caltech.Pointers to related work and some images from the thesis. How to get copies of the thesis.
(© 1994 Kurt Fleischer.)

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