def METHOD_NAME(i):
    num1     = np.array( [[fields[i].fields[0]( e1,e2 ) for e2 in etas[1]] for e1 in etas[0]] )
    num2     = np.array( [[fields[i].fields[1]( e1,e2 ) for e2 in etas[1]] for e1 in etas[0]] )
    C        = np.hypot(num1, num2)
    quadmesh.set_array(C)
    pbar.update()
    if i == len(fields) - 1:
        pbar.close()