Update Matplotlib 3D Graph Based on Real Time User Input - matplotlib

Question

I am trying to get matplotlib to create a dynamic 3d graph based on user input - but I can't get the graph to update. If I use the exact same code but without the "projection='3d'" setting, the program works correctly - but as soon as the graph is changed to display in 3d - it doesn't work.
Any help would be greatly appreciated.
3D Graph Code (graph doesn't update)
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.widgets import Slider
from mpl_toolkits.mplot3d import Axes3D
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
plt.subplots_adjust(left=0.25, bottom=0.25)
x = np.arange(0.0, 1.0, 0.1)
a0 = 5
b0 = 1
y = a0 * x + b0
z = np.zeros(10)
l, = plt.plot(x, y, z)
# Set size of Axes
plt.axis([0, 1, -10, 10])
# Place Sliders on Graph
ax_a = plt.axes([0.25, 0.1, 0.65, 0.03])
ax_b = plt.axes([0.25, 0.15, 0.65, 0.03])
# Create Sliders & Determine Range
sa = Slider(ax_a, 'a', 0, 10.0, valinit=a0)
sb = Slider(ax_b, 'b', 0, 10.0, valinit=b0)
def update(val):
a = sa.val
b = sb.val
l.set_ydata(a*x+b)
fig.canvas.draw_idle()
sa.on_changed(update)
sb.on_changed(update)
plt.show()
2D Graph Code (graph updates properly)
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.widgets import Slider
from mpl_toolkits.mplot3d import Axes3D
fig = plt.figure()
ax = fig.add_subplot(111)
plt.subplots_adjust(left=0.25, bottom=0.25)
x = np.arange(0.0, 1.0, 0.1)
a0 = 5
b0 = 1
y = a0 * x + b0
l, = plt.plot(x, y)
# Set size of Axes
plt.axis([0, 1, -10, 10])
# Place Sliders on Graph
ax_a = plt.axes([0.25, 0.1, 0.65, 0.03])
ax_b = plt.axes([0.25, 0.15, 0.65, 0.03])
# Create Sliders & Determine Range
sa = Slider(ax_a, 'a', 0, 10.0, valinit=a0)
sb = Slider(ax_b, 'b', 0, 10.0, valinit=b0)
def update(val):
a = sa.val
b = sb.val
l.set_ydata(a*x+b)
fig.canvas.draw_idle()
sa.on_changed(update)
sb.on_changed(update)
plt.show()

Answer 1

The line in the 3D case needs to be updated in all 3 dimensions (even the data in some dimension stays the same). In order to do so, you have to set the 2D data using set_data and the third dimension using set_3d_properties. So updating y would look like this:
l.set_data(x, a*x+b)
l.set_3d_properties(z)