The relationship between zero level set and thickness information

1. What is the purpose of computing the level set?
2. How does level set method work?

What is the purpose of computing the level set?

The advantage of the level-set model is that one can perform numerical computations involving curves and surfaces on a fixed Cartesian grid without having to parameterize these objects (this is called the Eulerian approach).

How does level set method work?

Level set method: Explanation

The level set method is just plain easy to understand: there is a surface, it intersects a plane, that gives us a contour and that's it. With image segmentation, the surface is updated with forces derived from the image.