  Animated textures can be used to visualize the spatial structure and temporal
evolution of vector fields at high spatial resolution. The animation requires
two time-dependent vector fields. The first of these vector fields determines
the spatial structure to be displayed. The second is a velocity field that
determines the time evolution of the field lines of the first vector field. We
illustrate this method with an example in magneto-quasi-statics, where the
second velocity field is taken to be the ExB drift velocity of electric
monopoles. This technique for displaying time-dependent electromagnetic fields
has three pedagogical advantages: (1) the continuous nature of the
representation underscores the action-by-contact nature of forces transmitted
by fields; (2) the animated texture motion shows the direction of
electromagnetic energy flow; and (3) the time-evolving field configuration
enables insights into Maxwell stresses.
