if you google LIC you’ll find a heap of papers about this relatively old technique of visualising vector fields. its handy as it shows you a true representation of forces (direction & magnitude) within a field.
ive stumbled onto this technique when researching streamlines. by definition, a line that is instantaneously tangent to the velocity vector of the vector flow.
this is what it looks like when you scatter a bunch of streamlines around a vector field.
the code came from this implementation and ive ported it over into OF.