Fluid Dynamics Seminar

Monday, Oct. 1, 2012, 4:00 PM
Cullimore, Room 611
New Jersey Institute of Technology


Computer Animation of Thin Liquid Splashes and Sheets

Christopher Batty


Columbia University Department of Computer Science



A wide range of visually intriguing effects exhibited by liquids involve the dynamics of thin sheets: the "milk crown" of a splashing droplet falling into a shallow pool, the periodic folding of poured chocolate sauce or cake batter, or the stunning splash formations captured by high speed artistic photography. The large aspect ratios of such sheets raise challenges for animation: capturing these effects with traditional volumetric simulation approaches requires extreme grid resolutions, with attendant memory and computational costs. In this talk, I will discuss some results of my ongoing work on this problem, highlighting two contrasting approaches.

The first technique I will describe combines a triangle mesh-based front tracking technique with an underlying Voronoi simulation mesh. The Voronoi mesh is rebuilt at each step from samples that are carefully placed to fully capture the detailed geometry of the liquid surface, while the use of embedded boundary methods avoids the need to exactly conform to physical boundaries. This method eliminates the accumulation of sub-grid noise in the surface geometry and ensures that even very thin splashes possess sufficient degrees of freedom for plausible animation, using far fewer samples than would be required with naive uniform refinement. The second method I will describe takes inspiration from dimensionally-reduced Lagrangian models commonly applied to elastic shells and cloth animation: we directly discretize a viscous liquid sheet as a deforming triangle-mesh surface with evolving thickness. I will illustrate that by exploiting the inherent geometry of the problem in this manner, we can reproduce an array of viscous sheet behaviours, including wrinkling, sagging, buckling, and surface tension, while exactly preserving liquid volume.