generate perlin noise without noise library

def generate_perlin_noise_2d(shape, res):
    def f(t):
        return 6*t**5 - 15*t**4 + 10*t**3
    
    delta = (res[0] / shape[0], res[1] / shape[1])
    d = (shape[0] // res[0], shape[1] // res[1])
    grid = np.mgrid[0:res[0]:delta[0],0:res[1]:delta[1]].transpose(1, 2, 0) % 1
    # Gradients
    angles = 2*np.pi*np.random.rand(res[0]+1, res[1]+1)
    gradients = np.dstack((np.cos(angles), np.sin(angles)))
    g00 = gradients[0:-1,0:-1].repeat(d[0], 0).repeat(d[1], 1)
    g10 = gradients[1:  ,0:-1].repeat(d[0], 0).repeat(d[