Metaballs, also known as blobby objects, are a type of implicit modeling technique.
We can think of a metaball as a partical surrounded by a density field, where
the density attributed to the particle (its influence) decreases with distance
from the particle location. A surface is implied by taking an isosurface through
this density field - the higher the isosurface value, the nearer it will be
to the particle.
Overview of Metaballs/Blobby Objects