Updating line in 3D plot Animation

Question

I am trying to plot a line in a 3D animation. I cant erase the plots i created in update_line. The problem is im always adding new lines. The best solution i see is to create the lines outside of the function and updating the data of those lines, but i cant seems to find a way for plot in 3D

first time posting, just a few hours of python. Learned nothing about canvas yet. Keep it simple please

import matplotlib; matplotlib.use("TkAgg")
import numpy as np
import matplotlib.pyplot as plt
import mpl_toolkits.mplot3d.axes3d as p3
import matplotlib.animation as animation
dotinline = 101
nframe = 7
fig = plt.figure(figsize=(16, 8))
ax = p3.Axes3D(fig)
ax.view_init(0, 90)


def init():
    ax.plot([-10, 10], [0, 0], [0, 0], "k")
    ax.plot([0, 0], [-10, 10], [0, 0], "k")
    ax.plot([0, 0], [0, 0], [-10, 10], "k")
    ax.plot([], [], [], "b")


def update_lines(index):
    seg = []
    x = np.linspace(-10, 10, dotinline)
    power = x**(-(nframe-1)/2+index)
    for i in range(len(x)-1):
        a = [x[i+1], x[i]]
        b = [0, 0]
        c = [power[i+1], power[i]]
        seg.append([a, b, c])
    for data in seg:
        ax.plot3D(data[0], data[1], data[2], "-b")


ax.set_xlim3d([-10, 10])
ax.set_xlabel('X')
ax.set_ylim3d([-10, 10])
ax.set_ylabel('Y')
ax.set_zlim3d([-10, 10])
ax.set_zlabel('Z')
ax.set_title('3D Test')


line_ani = animation.FuncAnimation(fig, update_lines, init_func=init, frames=nframe, interval=2000, blit=False)

plt.show()

Answer 1

Check this code:

import matplotlib; matplotlib.use("TkAgg")
import numpy as np
import matplotlib.pyplot as plt
import mpl_toolkits.mplot3d.axes3d as p3
import matplotlib.animation as animation
dotinline = 101
nframe = 7
fig = plt.figure(figsize=(16, 8))
ax = p3.Axes3D(fig)
ax.view_init(0, 90)


def init():
    ax.plot([-10, 10], [0, 0], [0, 0], "k")
    ax.plot([0, 0], [-10, 10], [0, 0], "k")
    ax.plot([0, 0], [0, 0], [-10, 10], "k")
    ax.plot([], [], [], "b")


def update_lines(index):
    ax.cla()
    init()
    seg = []
    x = np.linspace(-10, 10, dotinline)
    power = x**(-(nframe-1)/2+index)
    for i in range(len(x)-1):
        a = [x[i+1], x[i]]
        b = [0, 0]
        c = [power[i+1], power[i]]
        seg.append([a, b, c])
    for data in seg:
        ax.plot3D(data[0], data[1], data[2], "-b")


    ax.set_xlim3d([-10, 10])
    ax.set_xlabel('X')
    ax.set_ylim3d([-10, 10])
    ax.set_ylabel('Y')
    ax.set_zlim3d([-10, 10])
    ax.set_zlabel('Z')
    ax.set_title('3D Test')


line_ani = animation.FuncAnimation(fig, update_lines, init_func=init, frames=nframe, interval=2000, blit=False)

plt.show()

To erase the previous lines, just add ax.cla() .
However, this erase also the black line axis; so, after ax.cla() I run again init() , in order to re-draw the axes lines.
Finally, it is better to move the block:

ax.set_xlim3d([-10, 10])
ax.set_xlabel('X')
ax.set_ylim3d([-10, 10])
ax.set_ylabel('Y')
ax.set_zlim3d([-10, 10])
ax.set_zlabel('Z')
ax.set_title('3D Test')

inside the update_lines() function, in order to keep these options even when the lines are erased.
With this code, I get the following animation: