如何在matplotlib中进行3D革命？

Question

假设您有一条2D曲线,例如:

from matplotlib import pylab
t = numpy.linspace(-1, 1, 21)
z = -t**2
pylab.plot(t, z)

哪个产生

我想进行一场革命以获得一个3d图(见http://reference.wolfram.com/mathematica/ref/RevolutionPlot3D.html).绘制3d表面不是问题,但它不会产生我期望的结果:

如何在3d图中执行此蓝色曲线的旋转？

Answer 1

你的图上的图似乎使用笛卡尔网格。matplotlib 网站上有一些 3D 圆柱函数的示例，例如 Z = f(R)（此处：http ://matplotlib.org/examples/mplot3d/surface3d_radial_demo.html ）。这就是您要找的吗？以下是我通过函数 Z = -R**2 得到的结果：

要向您的函数添加截止，请使用以下示例：（需要 matplotlib 1.2.0）

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

fig = plt.figure()
ax = fig.gca(projection='3d')
X = np.arange(-5, 5, 0.25)
Y = np.arange(-5, 5, 0.25)
X, Y = np.meshgrid(X, Y)

Z = -(abs(X) + abs(Y))

## 1) Initial surface
# Flatten mesh arrays, necessary for plot_trisurf function
X = X.flatten()
Y = Y.flatten()
Z = Z.flatten()

# Plot initial 3D surface with triangles (more flexible than quad)
#surfi = ax.plot_trisurf(X, Y, Z, cmap=cm.jet, linewidth=0.2)

## 2) Cut off
# Get desired values indexes
cut_idx = np.where(Z > -5)

# Apply the "cut off"
Xc = X[cut_idx]
Yc = Y[cut_idx]
Zc = Z[cut_idx]

# Plot the new surface (it would be impossible with quad grid)
surfc = ax.plot_trisurf(Xc, Yc, Zc, cmap=cm.jet, linewidth=0.2)

# You can force limit if you want to compare both graphs...
ax.set_xlim(-5,5)
ax.set_ylim(-5,5)
ax.set_zlim(-10,0)

plt.show()

冲浪结果：

和冲浪：