来自 .npy 数据文件的 3d 箭袋图以提供 3d 矢量场

Question

I want to plot a 3d velocity vector field using a 3d quiver plot in python, from 3 data files (.npy) that give u, v and w components of velocity in the x, y and z directions. This what I have done so far, showing the error message as well. How do I create a 3d quiver plot from three 3d .npy data files? I have also looked at other examples here and here . The code below was adapted from the 2d quiver plot example from here .

import numpy as np
from matplotlib import pyplot as plt
from matplotlib.pyplot import figure
from mpl_toolkits.mplot3d import proj3d

c1 = 1
nx, ny, nz = 284, 160, 160

x1 = range(nx)
y1 = range(ny)
z1 = range(nz)

U = np.load("u.npy") # 3d array file
V = np.load("v.npy") # 3d array file
W = np.load("w.npy") # 3d array file

X1, Y1, Z1 = np.meshgrid(x1, y1, z1)

fig = plt.figure(figsize=(10,10))
ax = fig.gca(projection='3d')
ax.set_title("pivot='mid'; every 10th arrow; units='velocity vector' time=" + str(c1))
Q = ax.quiver(X1[::10, ::10], Y1[::10, ::10], Z1[::10, ::10], U[::10, ::10],
    V[::10, ::10], W[::10, ::10], pivot='mid', units='inches')

#Not sure if it should be formatted as below:
#Q = ax.quiver(X1[::10, ::10, ::10], Y1[::10, ::10, ::10], Z1[::10, ::10, ::10], U[::10, ::10, ::10],
            #V[::10, ::10, ::10], W[::10, ::10, ::10], pivot='mid', units='inches')
qk = ax.quiverkey(Q, 0.9, 0.9, 5, r'$1 \frac{m}{s}$', labelpos='E', coordinates='figure') #possibly for 2D (X, Y) only.
ax.scatter(X1[::10, ::10], Y1[::10, ::10], Z1[::10, ::10], color='c', s=0)
plt.tight_layout()
plt.savefig('3D_video_velocity_' + str(c1) + '.png')

Error message:

$ python3 test_3d_quiver_plot_1a.py 
Traceback (most recent call last):
  File "test_3d_quiver_plot_1a.py", line 69, in <module>
    Q = ax.quiver(X1[::10, ::10], Y1[::10, ::10], Z1[::10, ::10], U[::10, ::10],
  File "/home/brendan/.local/lib/python3.8/site-packages/mpl_toolkits/mplot3d/axes3d.py", line 2628, in quiver
    bcast = np.broadcast_arrays(*input_args, *masks)
  File "<__array_function__ internals>", line 5, in broadcast_arrays
  File "/home/brendan/.local/lib/python3.8/site-packages/numpy/lib/stride_tricks.py", line 264, in broadcast_arrays
    shape = _broadcast_shape(*args)
  File "/home/brendan/.local/lib/python3.8/site-packages/numpy/lib/stride_tricks.py", line 191, in _broadcast_shape
    b = np.broadcast(*args[:32])
ValueError: shape mismatch: objects cannot be broadcast to a single shape

The result should look something like this:

Answer 1

Based on the above comment, to create a 3D quiver plot X1, Y1, Z1, U, V, W must have the same shape.

Try to modify the following lines of code:

import numpy as np
nx, ny, nz = 160, 284, 160

x1 = range(nx)
y1 = range(ny)
z1 = range(nz)

X1, Y1, Z1 = np.meshgrid(x1, y1, z1)

Note that I changed nx, ny, nz = 284, 160, 160 to nx, ny, nz = 160, 284, 160 . This should give X1, Y1, Z1 the correct shape.

Answer 2

I found the following code produced a 3d quiver plot from 3 data files (3d arrrays in .npy files). The code was adapted from @tacaswell .

from mpl_toolkits.mplot3d import axes3d
import matplotlib.pyplot as plt
import numpy as np

nx, ny, nz = 160, 284, 160

x1 = range(nx)
y1 = range(ny)
z1 = range(nz)

u = np.load("u.npy")
v = np.load("v.npy")
w = np.load("w.npy")

fig = plt.figure(figsize=(10,10))
ax = fig.gca(projection='3d')

x, y, z = np.meshgrid(x1, y1, z1)

# 3d quiver plot for every 5th data point
ax.quiver(x[::5, ::5], y[::5, ::5], z[::5, ::5], u[::5, ::5], 
    v[::5, ::5], w[::5, ::5], length=0.1, color = 'red', lw=2)

plt.show()

The resultant 3d quiver plot is shown here (I haven't worked out how make the arrows larger yet):