Does anyone know how to draw 3D points so that they follow a clumped distribution? I know how to randomly or uniformly space them, but how to clump them?

One of many possible solutions is to define several centers of gravity (CGs), and then distribute the points so that each point lies close to some CG, with a certain offset. The direction is distributed uniformly, but the distance from target CG (lets call it D) may have probability proportional to D-2.