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UBC Theses and Dissertations

Interactive flow field modeling for the design and control of fluid motion in computer animation Gates, William Franklin


Ubiquitous and captivating, fluid—gaseous and liquid—motion is often desired in computer animation. For example, rives, lakes, and clouds enhance flights simulations. Realizing realistic fluid behaviour, however, can be difficult and laborious using traditional computer animation methods. Ad hoc kinematic models of fluid motion have been presented to facilitate the animation of fluids, but it is not clear how to extend or integrate these models to describe more general fluid motion. Simple dynamic models have been presented, but it is difficult to control the dynamic simulation to achieve the desired effect. To address this problem, a simple, hydrodynamically-based framework for realistically integrating models of fluid flow for computer animation purposes is presented. This framework is based on the continuity equation for incompressible flow, and allows flow fields to be linearly combined, regardless of whether they are interactively modeled or computed by dynamic simulation. Novel interactive flow field modeling methods are introduced to allow the animator to manipulate spline curves that correspond to streamlines in the flow field. The spline-based flow fields can be computed at interactive speed on standard graphics workstations. Many dynamic simulations produce flow fields that satisfy the continuity equation, and these can be linearly combined with the modeled flow field to define a mean flow field which is sampled at the nodes of a lattice. Turbulence is modeled by advecting stochastic distributions of models of vortex flow with the mean flow, allowing infinite resolution for small-scale complexity. Geometric models are advected using the final resulting flow field. A simple animation system incorporating the interactive flow modeling methods was implemented and shows this approach to be a promising and easily extendable method of realistically animating fluids.

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