Python中的箭头动画 [英] Arrow animation in Python

问题描述

首先，我刚刚开始学习Python。在过去的几个小时中，我一直在努力尝试更新箭头属性，以便在剧情动画期间更改它们。

First of all, I am just starting to learn Python. I have been struggling during the last hours trying to update the arrow properties in order to change them during a plot animation.

在彻底寻找答案之后，我检查了一下可以通过修改属性中心（例如 circle.center = new_coordinates ）来更改圆形补丁中心。但是，我找不到将这种机制外推到箭头补丁的方法...

After thoroughly looking for an answer, I have checked that it is possible to change a circle patch center by modifying the attribute 'center' such as circle.center = new_coordinates. However, I don't find the way to extrapolate this mechanism to an arrow patch...

到目前为止，代码是：

import numpy as np, math, matplotlib.patches as patches
from matplotlib import pyplot as plt
from matplotlib import animation

# Create figure
fig = plt.figure()    
ax = fig.gca()

# Axes labels and title are established
ax = fig.gca()
ax.set_xlabel('x')
ax.set_ylabel('y')

ax.set_ylim(-2,2)
ax.set_xlim(-2,2)
plt.gca().set_aspect('equal', adjustable='box')

x = np.linspace(-1,1,20) 
y  = np.linspace(-1,1,20) 
dx = np.zeros(len(x))
dy = np.zeros(len(y))

for i in range(len(x)):
    dx[i] = math.sin(x[i])
    dy[i] = math.cos(y[i])
patch = patches.Arrow(x[0], y[0], dx[0], dy[0] )


def init():
    ax.add_patch(patch)
    return patch,

def animate(t):
    patch.update(x[t], y[t], dx[t], dy[t])   # ERROR
    return patch,

anim = animation.FuncAnimation(fig, animate, 
                               init_func=init, 
                               interval=20,
                               blit=False)

plt.show()

尝试了几个选项之后，我认为功能更新可以使我更接近解决方案。但是，我得到了错误：

After trying several options, I thought that the function update could somehow take me closer to the solution. However, I get the error:

TypeError: update() takes 2 positional arguments but 5 were given

如果我仅通过定义动画功能（如下所示）在每个步骤中添加一个补丁，我得到的结果将显示在附件中。

If I just add one more patch per step by defining the animate function as shown below, I get the result shown in the image attached.

def animate(t):
    patch = plt.Arrow(x[t], y[t], dx[t], dy[t] )
    ax.add_patch(patch)
    return patch,

错误的动画

我试图添加一个patch.delete语句并创建一个新的补丁程序作为更新机制，但这会导致出现空动画...

I have tried to add a patch.delete statement and create a new patch as update mechanism but that results in an empty animation...

推荐答案

在 ax.add_patch（patch）之前添加 ax.clear（）

def animate(t):

    ax.clear() 

    patch = plt.Arrow(x[t], y[t], dx[t], dy[t] )
    ax.add_patch(patch)

    return patch,

---

编辑：：删除一个补丁

• 使用 ax.patches.pop（index）。

在您的示例中，只有一个补丁，因此您可以使用 index = 0

In your example is only one patch so you can use index=0

def animate(t):

    ax.patches.pop(0) 

    patch = plt.Arrow(x[t], y[t], dx[t], dy[t] )
    ax.add_patch(patch)

    return patch,

使用 ax.patches.remove（object）

需要 global 来获取/设置带有<$的外部 patch c $ c>箭头

It needs global to get/set external patch with Arrow

def animate(t):

    global patch

    ax.patches.remove(patch) 

    patch = plt.Arrow(x[t], y[t], dx[t], dy[t] )
    ax.add_patch(patch)

    return patch,

BTW：：获取可用于的属性列表update（）

print( patch.properties().keys() )

dict_keys(['aa', 'clip_path', 'patch_transform', 'edgecolor', 'path', 'verts', 'rasterized', 'linestyle', 'transform', 'picker', 'capstyle', 'children', 'antialiased', 'sketch_params', 'contains', 'snap', 'extents', 'figure', 'gid', 'zorder', 'transformed_clip_path_and_affine', 'clip_on', 'data_transform', 'alpha', 'hatch', 'axes', 'lw', 'path_effects', 'visible', 'label', 'ls', 'linewidth', 'agg_filter', 'ec', 'facecolor', 'fc', 'window_extent', 'animated', 'url', 'clip_box', 'joinstyle', 'fill'])

因此您可以使用 update 更改颜色-`facecolor

so you can use update to change color - `facecolor

def animate(t):
    global patch

    t %= 20 # get only 0-19 to loop animation and get color t/20 as 0.0-1.0

    ax.patches.remove(patch)

    patch = patches.Arrow(x[t], y[t], dx[t], dy[t])

    patch.update({'facecolor': (t/20,t/20,t/20,1.0)})

    ax.add_patch(patch)

    return patch,

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