### Summary
This paper adapts Fedkiw's smoke and liquid papers to present the fluid-computation results in a non-photorealistic manner.


### Problem

How do you adapt fluid-flow simulations (which can produce very realistic results for smoke and water) to generate cartoonish output? How do you make sure that the results are quick to render and show the most important details?


### Methods used

They take only the output of Fedkiw's solver and add massless marker particles to the simulation in much the same way that Fedkiw added particles in his later liquid paper. These particles are advected through the simulation velocity grid using Euler integration.

To do the actual rendering, rather than rendering the isosurface directly, they draw these particles as simple stencils, and then perform a depth-differencing algorithm to outline their shapes.


### Key ideas

Stencil rendering: can produce a variety of styles easily from the same underlying simulation.
Outlining: depth-differencing, performed on the rendered stencils, does a good job of outlining areas where the shape would otherwise be unclear (if rendered with similarly shaped/colored stencils)


### Questions

They performed these simulations only on smoke... what would liquids look like if rendered in the same way? How could we do better in that case?