Issue with shading and layering in 3D-plots

[khashabri]

Bug report

The following code should show a cylinder that is on a plane. However, as obvious in the 3rd and the 4th image, the shading and layering of matplotlib are not applied correctly and the result looks strange. Using zorder didn't also solve that.

Code for reproduction

import matplotlib.pyplot as plt
import numpy as np
from mpl_toolkits.mplot3d import Axes3D

# Help function to determine the cylinder plot data
def data_for_cylinder_along_z(center_x,center_y,center_z,radius,height_z):
    z = np.linspace(0, height_z, 50)
    theta = np.linspace(0, 2*np.pi, 50)
    theta_grid, z_grid=np.meshgrid(theta, z)
    x_grid = radius*np.cos(theta_grid) + center_x
    y_grid = radius*np.sin(theta_grid) + center_y
    z_grid = z_grid - height_z/2 + center_z
    return x_grid,y_grid,z_grid

# setting up a figure
fig = plt.figure(figsize=(10, 10))
ax = fig.gca(projection='3d')
ax.view_init(90, 0)
ax.set_xlabel('x')
ax.set_ylabel('y')
ax.set_zlabel('z')
ax.set_xlim3d(-1, 1)
ax.set_ylim3d(-1, 1)
ax.set_zlim3d(-1, 1)

# plotting a plane
yy, zz = np.meshgrid([-0.5, 0.5], [-0.5, 0.5])
ax.plot_surface(0, yy, zz, color='yellow')

# plotting a cylinder
r = 0.1
Xc,Yc,Zc = data_for_cylinder_along_z(r, 0, 0, r, 1)
ax.plot_surface(Xc, Yc, Zc)

plt.show()

Actual outcome

Expected outcome
The plane should be behind the cylinder in all images and the cylinder must be shown.

Matplotlib version

• Operating system: Ubuntu Linux 64-bit
• Matplotlib version: 3.1.1
• Matplotlib backend (print(matplotlib.get_backend())): Qt5Agg
• Python version: 3.7.3

[anntzer]

This is essentially the same issue as #12620: we know about it, but basically can't fix it.