### 2.1 Level-set-function parameterizations

The most general way to parameterize a 2-surface in a slice is to define a scalar “level-set function”
on some neighborhood of the surface, with the surface itself then being defined as the level set
Assuming the surface to be orientable, it is conventional to choose so that () outside
(inside) the surface. The choice of level-set function for a given surface is non-unique, but in general this is
not a problem.
This parameterization is valid for any surface topology including time-dependent topologies. The
2-surface itself can then be found by a standard isosurface-finding algorithm such as the marching-cubes
algorithm [105]. (This algorithm is widely used in computer graphics and is implemented in a number of
widely-available software libraries.)