Explicit Mesh Surfaces for Particle Based Fluids

Abstract

Figure 1: A drop falling into a shallow pool creates a water crown. AbstractWe introduce the idea of using an explicit triangle mesh to track the air/fluid interface in a smoothed particle hydrodynamics (SPH) simulator. Once an initial surface mesh is created, this mesh is carried forward in time using nearby particle velocities to advect the mesh vertices. The mesh connectivity remains mostly unchanged across time-steps; it is only modified locally for topology change events or for the improvement of triangle quality. In order to ensure that the surface mesh does not diverge from the underlying particle simulation, we periodically project the mesh surface onto an implicit surface defined by the physics simulation. The mesh surface gives us several advantages over previous SPH surface tracking techniques. We demonstrate a new method for surface tension calculations that clearly outperforms the state of the art in SPH surface tension for computer graphics. We also demonstrate a method for tracking detailed surface information (like colors) that is less susceptible to numerical diffusion than competing techniques. Finally, our temporally-coherent surface mesh allows us to simulate highresolution surface wave dynamics without being limited by the particle resolution of the SPH simulation.

Versatile surface tension and adhesion for SPH fluids

“…Recently, [Yu et al 2012] demonstrated that sub-particle scale capillary waves that are directly simulated on the fluid surface mesh can add a significant amount of detail to an existing simulation. We believe that our results would further improve by using their surface tracking and capillary wave simulation approach.…”

“…This is, however, not the case in previous surface area minimization techniques (e.g. [Morris 1999;Müller et al 2003;Yu et al 2012]), as they apply the forces to the particles as external forces. The effect of combining both terms can be seen in Figure 2c.…”

“…More recently, [Yu et al 2012] proposed another solution to the surface tension problem in SPH. In this work, the curvature is estimated on the fluid surface mesh, but the generated surface tension forces are applied to the adjacent fluid particles enclosed by the mesh.…”

“…[Müller et al 2003]), pairwise forces based on cohesion (e.g. [Becker and Teschner 2007]), a modified SPH formulation [Clavet et al 2005], and more recently forces based on surface mesh curvature [Yu et al 2012]. However, there is no single approach, which can handle very large surface tensions, avoids particle clustering at the free surface, minimizes surface curvature, and conserves momentum at the same time.…”

An Overview of Surface Tracking and Representation in Fluid Simulation

“…Small-scale viscous flows may support smoothing with over-damped surface tension and it may not be appropriate for inviscid liquid phenomena. To handle the lack of detailed surface motion when combining a lowresolution simulation and a detailed surface, Thurey et al [25] Bojsen-Hansen [23] and Yu et al [24] were proposed a highresolution dynamic surface waves. These methods masked the high resolution surface artifacts with rippling motions, but limited with unnecessary restrictions like height-field, shallow water, and constant wave speed assumptions.…”