Surface_plot: Add legend to facecolors

Question

Let's say I'm plotting something with two different surface colors, as follows in colors red and blue. I want to add two items to the legend, with a custom string and the color for each color in my set.

How would I do that?

# generate the plot
from mpl_toolkits.mplot3d import Axes3D
from matplotlib import cm
from matplotlib.ticker import LinearLocator, FormatStrFormatter
import matplotlib.pyplot as plt
import numpy as np
from numpy import random
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
X = np.arange(-5, 5, 0.25)
Y = np.arange(-5, 5, 0.25)
X, Y = np.meshgrid(X, Y)
R = np.sqrt(X**2 + Y**2)
Z = np.sin(R)
col1, col2 = cm.jet(np.array([0.1, 0.9]))
my_choice = random.choice([0, 1], size=X.shape)
my_color = my_choice[..., None] * col1[None, None, :] + (1 - my_choice)[..., None] * col2[None, None, :]
surf = ax.plot_surface(X, Y, Z, rstride=1, cstride=1, facecolors = my_color,
        linewidth=0, antialiased=False)
ax.set_zlim(-1.01, 1.01)
# customstrings for legend:
myLegendLabels = {0: 'very red', 1: 'very blue'}

Answer 1

You can do that with "proxy artists":

from mpl_toolkits.mplot3d import Axes3D
from matplotlib import cm
from matplotlib.ticker import LinearLocator, FormatStrFormatter
import matplotlib.pyplot as plt
import matplotlib.patches as mpatches
import numpy as np
from numpy import random

# generate the plot
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
X = np.arange(-5, 5, 0.25)
Y = np.arange(-5, 5, 0.25)
X, Y = np.meshgrid(X, Y)
R = np.sqrt(X**2 + Y**2)
Z = np.sin(R)
col1, col2 = cm.jet(np.array([0.1, 0.9]))
my_choice = random.choice([0, 1], size=X.shape)
my_color = my_choice[..., None] * col1[None, None, :] + (1 - my_choice)[..., None] * col2[None, None, :]
surf = ax.plot_surface(X, Y, Z, rstride=1, cstride=1, facecolors = my_color,
        linewidth=0, antialiased=False)
ax.set_zlim(-1.01, 1.01)
# Add legend with proxy artists
col1_patch = mpatches.Patch(color=col1, label='very blue')
col2_patch = mpatches.Patch(color=col2, label='very red')
plt.legend(handles=[col1_patch, col2_patch])

Result: