compute_field.py 文件源码

def base_vectors(n):
    """ Returns 3 orthognal base vectors, the first one colinear to n.
    """
    # normalize n
    n = n / np.sqrt(np.square(n).sum(axis=-1))

    # choose two vectors perpendicular to n
    # choice is arbitrary since the coil is symetric about n
    if abs(n[0]) == 1 :
        l = np.r_[n[2], 0, -n[0]]
    else:
        l = np.r_[0, n[2], -n[1]]

    l = l / np.sqrt(np.square(l).sum(axis=-1))
    m = np.cross(n, l)
    return n, l, m