Physically-based Simulation For Highly Detailed Fluids

With the development of numerical techniques, it is common to use simulation meth-ods to produce visually attractive fluid effects in movie industries. The small-scale visual details, such as swirling vortices in rising smoke and small granular particles in flowing sand, is essential in such simulations. In this thesis, two new methods are presented for capturing and preserving the visual details in fluid and sand animation efficiently and precisely.First, this paper presents a new efficient method for animating sand and other gran-ular materials in 3D scenes. Our method couples 2D and 3D simulation techniques in a physically based way. A surface flow model of granular material-the BCRE model-is used to separate sand piles into two layers:a surface flowing layer and a static layer. The surface layer is simulated using discrete element method (DEM) to capture the detailed flowing behavior, while the invisible and static layer is represented by a height field for efficiency. The matter transfer between the two layers is modeled based on the surface flow equations through a particle interface. We demonstrate that our method leads to sig-nificant improvements of computational efficiency compared to standard discrete element method, without sacrificing the rich 3D animation effects.Second, We present a new method to create and preserve the turbulent details gener-ated around moving objects in SPH fluid. In our approach, a high-resolution overlapping grid is bounded to each object and translates with the object. The turbulence formation is modeled by resolving the local flow around objects using a hybrid SPH-FLIP method. Then these vortical details are carried on SPH particles flowing through the local region and preserved in the global field in a synthetic way. Our method provides a physically plausible way to model the turbulent details around both rigid and deformable objects in SPH fluid, and can efficiently produce animations of complex gaseous phenomena with rich visual details.