如何在 matplotlib 中更新 3D 箭头动画 [英] How to update 3D arrow animation in matplotlib

问题描述

我正在尝试使用 matplotlib 在 python 中重现

我能够使用 3D quiver 函数生成矢量箭头，但是当我

那么，问题是:如何生成多个不同长度的 3D 箭头?重要的是，我能否以这样一种方式生成它们，以便我可以轻松地针对动画的每一帧进行修改?

到目前为止，这是我的代码，使用不太有希望的 3D quiver 方法:

将 numpy 导入为 np导入 matplotlib.pyplot 作为 plt导入 mpl_toolkits.mplot3d.axes3dax1 = plt.subplot(111,projection='3d')t = np.linspace(0,10,40)y = np.sin(t)z = np.sin(t)line, = ax1.plot(t,y,z,color='r',lw=2)ax1.quiver(t,y,z, t*0,y,z)plt.show()

解决方案

正如 Azad 所建议的，一个不优雅但有效的解决方案是简单地编辑 mpl_toolkits/mplot3d/axes3d.py 以删除规范化.由于我不想弄乱我的实际 matplotlib 安装，我只是将axes3d.py 文件复制到与我的其他脚本相同的目录并修改了该行

norm = math.sqrt(u ** 2 + v ** 2 + w ** 2)

到

范数 = 1

(一定要更改正确的行.norm"还有一个用法要高几行.)此外，为了让axes3d.py在mpl目录之外时正常运行，我更改了

来自 .导入 art3d从 .导入 proj3d从 .导入axis3d

到

from mpl_toolkits.mplot3d import art3d从 mpl_toolkits.mplot3d 导入 proj3d从 mpl_toolkits.mplot3d 导入axis3d

这是我能够生成的漂亮动画(不确定颜色出了什么问题，在我上传到 SO 之前看起来不错).

以及生成动画的代码:

将 numpy 导入为 np导入 matplotlib.pyplot 作为 plt导入axes3d_hackedax1 = plt.subplot(111,projection='3d')plt.ion()plt.show()t = np.linspace(0,10,40)对于索引，枚举延迟(np.linspace(0,1,20)):y = np.sin(t+delay)z = np.sin(t+delay)如果延迟>0:行.remove()ax1.collections.remove(linecol)line, = ax1.plot(t,y,z,color='r',lw=2)linecol = ax1.quiver(t,y,z, t*0,y,z)plt.savefig('图像/帧%03i.gif'%index)plt.draw()plt.ioff()plt.show()

现在，如果我能让这些箭头看起来更漂亮，头部饱满就好.但这是一个单独的问题...

将来，matplotlib 不会根据此 拉取请求.

I am trying to reproduce the left plot of this animation in python using matplotlib.

I am able to generate the vector arrows using the 3D quiver function, but as I read here, it does not seem possible to set the lengths of the arrows. So, my plot does not look quite right:

So, the question is: how do I generate a number of 3D arrows with different lengths? Importantly, can I generate them in such a way so that I can easily modify for each frame of the animation?

Here's my code so far, with the not-so-promising 3D quiver approach:

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

ax1 = plt.subplot(111,projection='3d')

t = np.linspace(0,10,40)

y = np.sin(t)
z = np.sin(t)
line, = ax1.plot(t,y,z,color='r',lw=2)

ax1.quiver(t,y,z, t*0,y,z)
plt.show() 

解决方案

As Azad suggests, an inelegant, but effective, solution is to simply edit the mpl_toolkits/mplot3d/axes3d.py to remove the normalization. Since I didn't want to mess with my actual matplotlib installation, I simply copied the axes3d.py file to the same directory as my other script and modified the line

norm = math.sqrt(u ** 2 + v ** 2 + w ** 2)

to

norm = 1

(Be sure to change the correct line. There is another use of "norm" a few lines higher.) Also, to get axes3d.py to function correctly when it's outside of the mpl directory, I changed

from . import art3d
from . import proj3d
from . import axis3d

to

from mpl_toolkits.mplot3d import art3d
from mpl_toolkits.mplot3d import proj3d
from mpl_toolkits.mplot3d import axis3d

And here is the nice animation that I was able to generate (not sure what's going wrong with the colors, it looks fine before I uploaded to SO).

And the code to generate the animation:

import numpy as np
import matplotlib.pyplot as plt
import axes3d_hacked

ax1 = plt.subplot(111,projection='3d')
plt.ion()
plt.show()

t = np.linspace(0,10,40)

for index,delay in enumerate(np.linspace(0,1,20)):
    y = np.sin(t+delay)
    z = np.sin(t+delay)

    if delay > 0:
        line.remove()
        ax1.collections.remove(linecol)

    line, = ax1.plot(t,y,z,color='r',lw=2)
    linecol = ax1.quiver(t,y,z, t*0,y,z)

    plt.savefig('images/Frame%03i.gif'%index)
    plt.draw()

plt.ioff()
plt.show()

Now, if I could only get those arrows to look prettier, with nice filled heads. But that's a separate question...

EDIT: In the future, matplotlib will not automatically normalize the arrow lengths in the 3D quiver per this pull request.

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