Ph.D Thesis, Department of Computer Science, KU Leuven, Celestijnenlaan 200A, 3001 Heverlee, Belgium, December 2009.
Today's computer animations and movies with special effects have reached a high level of realism and complexity. Modeling and animation software has become more and more versatile and offers state of the art algorithms mimicking our real world. Amongst those algorithms are the physics-based methods for solving the dynamics of real-life phenomena. This dissertation covers such algorithms for the simulation of fluid behavior and the dynamics of objects. We specifically concentrate on the mutual interactions between fluids and objects. Generally previous systems only simulate the geometry of objects in combination with fluids, therefore treating the object as an impenetrable solid. Yet most objects are made out of porous materials such as sponges or cloth, meaning they absorb and diffuse fluid through their body upon interaction, which affects their physical behavior. In this work we present a novel simulation algorithm for porous flow through a wide variety of fluid-absorbent deformable objects and granular volumes. We introduce the physical principles governing porous flow, expressed by the law of Darcy, into a Smoothed Particle Hydrodynamics (SPH) framework, making fluid absorption and fluid flow inside the porous material possible. We show how secondary effects of the absorbed fluid on the porous material can be incorporated in existing particle-based SPH frameworks for simulating rigid bodies, elastic bodies, cloth and granular materials. This leads to the animation of new unseen effects including mass and buoyancy changes, weakening of elastic materials, sticky wet cloth, moist sand sculptures and mud formation. To accommodate the new porous flow algorithm we build a large particle-based framework. We not only implement various existing algorithms for simulating fluid flow, elastic bodies, rigid bodies and granular materials in one unifying framework, but we also create new simulation algorithms for cloth and sand in the same unifying manner. We also present a software architecture for such a unified SPH system to provide a solid foundation for particle simulations and interactions. In the design of these simulation models attention was spend on both the physics aspects as the creativity of the animator. The result is a physics-based animation package combining flexibility and solid simulation tools. Each of the presented simulation algorithms is therefore illustrated with several short computer animations showing the particular new effects.
