“管"Python 中的箭头 [英] "Tube" Arrows in Python

问题描述

我正在寻找一种用 python 绘制几个 (O(1)) 3D 箭头的方法，它们是适当的 3D"，我的意思是指与 Mathematica 产生的类似的东西，即箭头的杆看起来就像一根管子.

I am looking for a way to draw a few (O(1)) 3D arrows with python, which are "proper 3D", by which I mean something along the lines of what Mathematica yields, i.e. rod of the arrow looks like a tube.

我在 matplotlib 文档中没有找到任何内容，但肯定有办法吗?

I did not find anything in the matplotlib documentation, but surely there must be a way?

推荐答案

您可以从 2D 中定义的某些路径创建旋转实体以创建 3D 箭头.下面的代码将它包装成一个函数，它允许指定一些箭头参数.这允许创建要使用的路径.然后绕 z 轴旋转，创建一个 3D 箭头.为了允许箭头在空间中的任意方向，然后可以围绕 x 轴旋转完整的箭头，然后围绕 z 轴(theta_x，theta_z).最后使用 plot_surface 绘制箭头.请注意，放置箭头的轴应该具有相同的方面，以便箭头不会倾斜.

You may create a solid of revolution from some path defined in 2D to create a 3D arrow. The following code wraps this into a function, which allows to specify some of the arrow parameters. This allows to create the path to be used. This is then revolved about the z axis, creating a 3D arrow. To allow for arbitrary orientations of the arrow in space, one may then rotate the complete arrow about the x axis and then about the z axis (theta_x, theta_z). Finally the arrow is plotted using a plot_surface. Note that the axes into which the arrow is placed should have an equal aspect, such that the arrow is not skewed.

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


def arrow3d(ax, length=1, width=0.05, head=0.2, headwidth=2,
                theta_x=0, theta_z=0, offset=(0,0,0), **kw):
    w = width
    h = head
    hw = headwidth
    theta_x = np.deg2rad(theta_x)
    theta_z = np.deg2rad(theta_z)

    a = [[0,0],[w,0],[w,(1-h)*length],[hw*w,(1-h)*length],[0,length]]
    a = np.array(a)

    r, theta = np.meshgrid(a[:,0], np.linspace(0,2*np.pi,30))
    z = np.tile(a[:,1],r.shape[0]).reshape(r.shape)
    x = r*np.sin(theta)
    y = r*np.cos(theta)

    rot_x = np.array([[1,0,0],[0,np.cos(theta_x),-np.sin(theta_x) ],
                      [0,np.sin(theta_x) ,np.cos(theta_x) ]])
    rot_z = np.array([[np.cos(theta_z),-np.sin(theta_z),0 ],
                      [np.sin(theta_z) ,np.cos(theta_z),0 ],[0,0,1]])

    b1 = np.dot(rot_x, np.c_[x.flatten(),y.flatten(),z.flatten()].T)
    b2 = np.dot(rot_z, b1)
    b2 = b2.T+np.array(offset)
    x = b2[:,0].reshape(r.shape); 
    y = b2[:,1].reshape(r.shape); 
    z = b2[:,2].reshape(r.shape); 
    ax.plot_surface(x,y,z, **kw)

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')

arrow3d(ax)

arrow3d(ax, length=2, width=0.02, head=0.1, headwidth=1.5, offset=[1,1,0], 
        theta_x=40,  color="crimson")

arrow3d(ax, length=1.4, width=0.03, head=0.15, headwidth=1.8, offset=[1,0.1,0], 
        theta_x=-60, theta_z = 60,  color="limegreen")

ax.set_xlim(0,1)
ax.set_ylim(0,1)
ax.set_zlim(0,1)
plt.show()

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