Squish is an algorithm that works on meshes. Squish flattens the mesh by "minimizing the changes in facet area and changes in facet edge lengths" between the 3‑D mesh and the 2‑D mesh, subject to some constraints.

For example, if A,B,C are the corners of a 3‑D triangle and a,b,c are the corresponding corners of the 2‑D triangle, the changes in edge length are

The "minimizing the changes in area and or edge lengths" above means create the 2‑D mesh so that "D" is as small as possible.

In practice, there are thousands of facets and many ways to minimize D, most of which don't make practical sense. So Squish constrains the answer to prevent the 2‑D mesh from folding back onto itself and forcing certain 3‑D points end up in specified 2‑D locations.

A trimmed NURBS surface is squished by squishing a dense mesh of the surface.

The squish options determine how DA, DA2, D1 and D2 are combined and allow for more complicated ways to calculate of DA, DA2, D1, and D2 and to allow for a bias towards stretching or compression.

However, the Squish algorithm is much too simple to even begin to model the true physical properties of most materials that come in sheets, particularly those that where material thickness plays a role and those that can compress or stretch any appreciable amount,

In short, if a sheet of material is expensive, cutting it is expensive, or bending it is expensive, or related issues in the manufacturing process are time critical or money critical, then consider using Squish to give you an initial hint about the shape of a pattern, but real material and manufacturing expertise will have to be used to create a pattern that will work on the shop floor.