pythonmatplotlibmatplotlib-3d

Plot surfaces on a cube

I would like to plot surfaces to a cube with matplotlib. I am trying to use ax.plot_surface(X, Y, Z), however I am a bit confused. What should the X, Y and Z represent as 2D arrays?

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

points = np.array([[-1, -1, -1],
                      [1, -1, -1 ],
                      [1, 1, -1],
                      [-1, 1, -1],
                      [-1, -1, 1],
                      [1, -1, 1 ],
                      [1, 1, 1],
                      [-1, 1, 1]])

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
# ax.plot_surface(X, Y, Z)  # how?
ax.scatter3D(points[:, 0], points[:, 1], points[:, 2])
ax.set_xlabel('X')
ax.set_ylabel('Y')
ax.set_zlabel('Z')
plt.show()
Solution

  • Each face of the cube is a surface for which you can either define each corner yourself, or use meshgrid:

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

points = np.array([[-1, -1, -1],
                      [1, -1, -1 ],
                      [1, 1, -1],
                      [-1, 1, -1],
                      [-1, -1, 1],
                      [1, -1, 1 ],
                      [1, 1, 1],
                      [-1, 1, 1]])

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
r = [-1,1]
X, Y = np.meshgrid(r, r)
z = np.array([[1, 1]])
ax.plot_surface(X,Y, 1*z, alpha=0.5)
ax.plot_surface(X,Y,-1*z, alpha=0.5)
ax.plot_surface(X,-1*z,Y, alpha=0.5)
ax.plot_surface(X,1*z,Y, alpha=0.5)
ax.plot_surface(1*z,X,Y, alpha=0.5)
ax.plot_surface(-1*z,X,Y, alpha=0.5)
ax.scatter3D(points[:, 0], points[:, 1], points[:, 2])
ax.set_xlabel('X')
ax.set_ylabel('Y')
ax.set_zlabel('Z')
plt.show()

    enter image description here

    X,Y, and Z are (the same) list of 2D points:

    >>> numpy.meshgrid([-1,1], [-1,1])
[array([[-1,  1],
       [-1,  1]]), array([[-1, -1],
       [ 1,  1]])]