Visibility of lines in a 3D plot-CodePudding

In my wishful thinking, the black line from (0, 0, 1) to (1, 0, 1) should be completely visible.

What should I do to get a sensible graph?

My mwe

In [37]: import numpy as np
    ...: import matplotlib.pyplot as plt
    ...: 
    ...: fig, ax = plt.subplots(subplot_kw=dict(projection="3d"), constrained_layout=1)
    ...: 
    ...: x = y = np.linspace(0, 1, 11)
    ...: X, Y = np.meshgrid(x, y)
    ...: Z = X Y
    ...: 
    ...: ax.plot_surface(X, Y, Z)
    ...: ax.plot3D([0,1,1,0,0],[0,0,1,1,0],[1,1,1,1,1], color='k', lw=3)
    ...: plt.show()

CodePudding user response：

Do you mean like this? I've added "zorder" to your plot3D code.

import numpy as np
import matplotlib.pyplot as plt
fig, ax = plt.subplots(subplot_kw=dict(projection="3d"), constrained_layout=1)
x = y = np.linspace(0, 1, 11)
X, Y = np.meshgrid(x, y)
Z = X Y
 
ax.plot_surface(X, Y, Z)
ax.plot3D([0,1,1,0,0],[0,0,1,1,0],[1,1,1,1,1], color='k', lw=3, zorder=3)
plt.show()

Output:

CodePudding user response：

What I have noticed is that, the way matplotlib currently works, any polygon is either fully in front of any other polygon, or fully behind it.

If you know the intersection lines, you could display not your original polygons, but several polygons equivalent to the original ones broken by the intersection lines. Like this, the display will be correct.

It will probably be the same with plots etc., I have not checked, but polygons should be enough in the case you are asking about.

import matplotlib.pyplot as plt
import mpl_toolkits.mplot3d as a3

fig, ax = plt.subplots(subplot_kw=dict(projection="3d")) 
blue_coords_1 = [[0, 0, 0], [1, 0, 1/2], [0, 1, 1/2] ]
blue_coords_2 = [[1, 0, 1/2], [1, 1, 1], [0, 1, 1/2] ]

none_coords_1 = [[0, 0, 1/2], [1, 0, 1/2], [0, 1, 1/2]]
none_coords_2 = [[1, 0, 1/2], [1, 1, 1/2], [0, 1, 1/2]]

all_polys = a3.art3d.Poly3DCollection([none_coords_1, none_coords_2, blue_coords_1, blue_coords_2], facecolors=['blue', 'blue', 'red', 'red'], edgecolors=['none', 'none', 'black', 'black'])
ax.add_collection3d(all_polys)

plt.show()