ctrl_pts = [
    [[0, 0, 20],  [100, 0, -35],   [200, 0, 60],    [300, 0, 5]],
    [[0, 100, 30], [100, 100, -25], [200, 100, 120], [300, 100, 5]],
    [[0, 200, 0], [100, 200, 35],  [200, 200, 60],  [300, 200, 45]],
    [[0, 300, 0], [100, 300, -35], [200, 300, 60],  [300, 300, 45]]
];
ctrl_pts[0][0][2] = 2;