Animating Sand as a Surface Flow

This paper presents a new efficient method for animating sand and other granular 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 significant improvements of computational efficiency compared to standard discrete element method, without sacrificing the rich 3D animation effects.