Plotting a 3D Cube, a Sphere and a Vector in Matplotlib

Plotting a 3d cube, a sphere and a vector in Matplotlib

It is a little complicated, but you can draw all the objects by the following code:

from mpl_toolkits.mplot3d import Axes3D
import matplotlib.pyplot as plt
import numpy as np
from itertools import product, combinations

fig = plt.figure()
ax = fig.gca(projection='3d')
ax.set_aspect("equal")

# draw cube
r = [-1, 1]
for s, e in combinations(np.array(list(product(r, r, r))), 2):
    if np.sum(np.abs(s-e)) == r[1]-r[0]:
        ax.plot3D(*zip(s, e), color="b")

# draw sphere
u, v = np.mgrid[0:2*np.pi:20j, 0:np.pi:10j]
x = np.cos(u)*np.sin(v)
y = np.sin(u)*np.sin(v)
z = np.cos(v)
ax.plot_wireframe(x, y, z, color="r")

# draw a point
ax.scatter([0], [0], [0], color="g", s=100)

# draw a vector
from matplotlib.patches import FancyArrowPatch
from mpl_toolkits.mplot3d import proj3d

class Arrow3D(FancyArrowPatch):

    def __init__(self, xs, ys, zs, *args, **kwargs):
        FancyArrowPatch.__init__(self, (0, 0), (0, 0), *args, **kwargs)
        self._verts3d = xs, ys, zs

    def draw(self, renderer):
        xs3d, ys3d, zs3d = self._verts3d
        xs, ys, zs = proj3d.proj_transform(xs3d, ys3d, zs3d, renderer.M)
        self.set_positions((xs[0], ys[0]), (xs[1], ys[1]))
        FancyArrowPatch.draw(self, renderer)

a = Arrow3D([0, 1], [0, 1], [0, 1], mutation_scale=20,
            lw=1, arrowstyle="-|>", color="k")
ax.add_artist(a)
plt.show()

Plot surfaces on a cube

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)
ax.plot_surface(X,Y,1, alpha=0.5)
ax.plot_surface(X,Y,-1, alpha=0.5)
ax.plot_surface(X,-1,Y, alpha=0.5)
ax.plot_surface(X,1,Y, alpha=0.5)
ax.plot_surface(1,X,Y, alpha=0.5)
ax.plot_surface(-1,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()

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]])]

I have a problem with plotting sphere and a curve on it

Using spherical coordinates, you can easily do that:

## plot a circle on the sphere using spherical coordinate.
import numpy as np
import matplotlib.pyplot as plt

# a complete sphere
R = 10
theta = np.linspace(0, 2 * np.pi, 1000)
phi = np.linspace(0, np.pi, 1000)
x_sphere = R * np.outer(np.cos(theta), np.sin(phi))
y_sphere = R * np.outer(np.sin(theta), np.sin(phi))
z_sphere = R * np.outer(np.ones(np.size(theta)), np.cos(phi))

# a complete circle on the sphere
x_circle = R * np.sin(theta)
y_circle = R * np.cos(theta)

# 3d plot
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.plot_surface(x_sphere, y_sphere, z_sphere, color='blue', alpha=0.2)
ax.plot(x_circle, y_circle, 0, color='green')
plt.show()

Plotting a surface (sphere) in matplotlib, centered on coordinates other then 0,0,0

Just add the coordinates of the center to x, y and z.

x = r * np.outer(np.cos(u), np.sin(v)) + center_x
y = r * np.outer(np.sin(u), np.sin(v)) + center_y
z = r * np.outer(np.ones(np.size(u)), np.cos(v)) + center_z

---

Related Topics