### Summary 
This paper describes the particle level set method for tracking an evolving liquid interface using the fluid flow velocity solver described in Stable Fluids
### Problem
Liquids require a well-defined interface to visualize well, but level sets and density data by themselves result in volume loss.  Particles, on the other hand, don't provide a continuous interface.
### Methods Used 
This paper extends the ideas in Stable Fluids, using the determined velocity field to advect both a set of particles and level set, using each to correct inaccuracies in the other.  The level set is used in areas of low curvature, and the particles are used to correct areas of high curvature.
### Key Ideas 
* Particles and level sets can complement each other to resolve problem areas
* A local signed distance function can be generated for particles, which can be added (union-ed) to a level set to correct it
* This local distance function can be smoothed to remove visual artifacts (this step is not used in later implementations we've seen)
* The fast marching method can recreate a signed distance function after correction