def alignment_matrix_3D(u, v):
<EOL>u = normalize(u)<EOL>v = normalize(v)<EOL>w = np.cross(u, v)<EOL>th = vector_angle(u, v)<EOL>return rotation_matrix_3D(w, th)<EOL>
alignment_matrix_3D(u, v) yields a 3x3 numpy array that rotates the vector u to the vector v
around the origin.