First of all you need to notice that no geometry changes at all. Basically we use two different meshes: a very regular grid and a very irregular mesh that was created by randomly slicing a cube.
Then there is a pixelshader that calculates a potential field of 4 points. The potential is shredded with sin() and modulo and then all pixels inside a certain range are rejected with "clip()". As a final touch, pixels near the border are tinted.
To make it more interesting, we first introduce a vertex shader that wobbles the mesh a bit.
The cell like effect is made by adding a texture to the potential field.