This paper addresses the control and interactive animation of swarms for tasks specified in relative configuration way. Several control goals are of interest: aggregation, formation, and rendezvous. This paper summarizes in a unified framework control systems for achieving these basic objectives. The performance of the corresponding control systems is illustrated by a JAVA-based application developed to visualize the swarm behavior. This is an interactive animation tool which improves the understanding of and intuition for a number of aspects dealing with the swarms tasks. This tool allows directly manipulating graphical representation of the systems such as a choice among formation structures, initial configuration of the swarm, and control parameters, and getting instant feedback on the effects.