Matplotlib code for 3D line animation on top of a 3D surface

Question

I am trying to create a 3D line animation, on top of a 3D surface plot in matplotlib.

I am able to plot the 3D surface, but there is no animation. And there is no error in the code. I am setting the X,Y and Z values of the 3D line upto the current frame.

import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits import mplot3d
from matplotlib import animation

def f(x,y):
    return x+y

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
X = np.arange(0, 10, 1)
Y = np.arange(0, 10, 1)
Z = X+Y

X1, Y1 = np.meshgrid(X, Y)
Z1 = f(X1, Y1)
ax.plot_surface(X1, Y1, Z1, color='b', alpha=0.5)
plt.show()

line, = ax.plot([], [], [], lw=2)
def init():
    line.set_data([], [])
    line.set_3d_properties([])
    return line
def animate(i, line, X, Y, Z):
    line.set_data(X[:i], Y[:i])
    line.set_3d_properties(Z[:i])
    return line
anim = animation.FuncAnimation(fig, animate, init_func=init, fargs=(line, X, Y, Z),
                           frames=10, interval=200,
                           repeat_delay=5, blit=True)
plt.show()

Answer 1

1. You don't get any error, because you call plt.show() before any animation is even defined. Remove the first plt.show() .

2. You will then get errors as expected. The problem is that you need to return a list of artists from the animating functions when using blit=True . This is easily achieved by adding a comma,

    return line,

Complete code:

import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits import mplot3d
from matplotlib import animation

def f(x,y):
    return x+y

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
X = np.arange(0, 10, 1)
Y = np.arange(0, 10, 1)
Z = X+Y

X1, Y1 = np.meshgrid(X, Y)
Z1 = f(X1, Y1)
ax.plot_surface(X1, Y1, Z1, color='red', alpha=0.5)

line, = ax.plot([], [], [], lw=2)

def init():
    line.set_data([], [])
    line.set_3d_properties([])
    return line,

def animate(i, line, X, Y, Z):
    line.set_data(X[:i], Y[:i])
    line.set_3d_properties(Z[:i])
    return line,

anim = animation.FuncAnimation(fig, animate, init_func=init, fargs=(line, X, Y, Z),
                           frames=10, interval=200,
                           repeat_delay=5, blit=True)
plt.show()