移动物体后如何更新颤动图？

Question

我正在编写一个小型可视化项目，假设在几个带电体周围显示矢量场。

我的问题是下一个： 我不知道如何在从主要位置移动圆圈（带电粒子）后更新颤动场。

链接到图片，因为我的声誉太低了。我几乎是 stackoverflow 的新手。

from pylab import *
from scipy import *
import matplotlib.pyplot as plt
import matplotlib.patches as patches
import scipy.constants as const
skr = const.pi*const.epsilon_0*4

class DraggablePoint:
    def __init__(self, p, q0):
        self.q = q0
        self.point = p
        self.c_kruznice = p.center
        self.press = None

    def connect(self):
        self.cidpress = self.point.figure.canvas.mpl_connect('button_press_event', self.button_press_event) 
        self.cidrelease = self.point.figure.canvas.mpl_connect('button_release_event',self.button_release_event)   
        self.cidmotion = self.point.figure.canvas.mpl_connect('motion_notify_event', self.motion_notify_event)  

    def disconnect(self):
        self.point.figure.canvas.mpl_disconnect(self.cidpress)
        self.point.figure.canvas.mpl_disconnect(self.cidrelease)
        self.point.figure.canvas.mpl_disconnect(self.cidmotion)


    def button_press_event(self,event):
        if event.inaxes != self.point.axes:
            return
        contains = self.point.contains(event)[0]
        if not contains: return
        self.press = self.point.center, event.xdata, event.ydata


    def button_release_event(self,event):
        self.press = None
        self.point.figure.canvas.draw()

    def motion_notify_event(self, event):
        if self.press is None: return
        if event.inaxes != self.point.axes: return
        self.point.center, xpress, ypress = self.press
        dx = event.xdata - xpress
        dy = event.ydata - ypress
        self.point.center = (self.point.center[0]+dx, self.point.center[1]+dy)
        print(self.point.center)
        self.point.figure.canvas.draw()

if __name__ == '__main__':
    f_s=0.3
    def R(x,y):
        r=np.sqrt(x**2+y**2)+f_s
        return r

    def polje(tela, X, Y):
        Ex = 0
        Ey = 0
        for i in range(len(tela)):
            r=R(tela[i].c_kruznice[0] - X, tela[i].c_kruznice[1] - Y )
            ex = X - tela[i].c_kruznice[0]
            ey = Y - tela[i].c_kruznice[1]
            Ex += (tela[i].q/skr)*(1/(r+f_s)**3)*ex
            Ey += (tela[i].q/skr)*(1/(r+f_s)**3)*ey
        return Ex, Ey

    fig = plt.figure(figsize=(8,8))
    ax = fig.add_axes([0.05,0.05,0.92,0.92])
    ax.set_xlim(-6,6)
    ax.set_ylim(-6,6)
    scale = 0.2
    X,Y=np.mgrid[-5:5:scale, -5:5:scale]

    circles = []
    q=3*const.e
    s=abs(q)
    sx=sqrt(s/np.pi)*1e8*5
    circle2 = patches.Circle((3,0.3), 0.3, fc='r', alpha=0.5, picker=True)
    circle1 = patches.Circle((0.7,0.3), 0.3, fc='r', alpha=0.5, picker=True)
    circle = patches.Circle((-4,0.3), 0.3, fc='b', alpha=0.5, picker=True)
    circles.append(ax.add_patch(circle1))
    circles.append(ax.add_patch(circle))
    circles.append(ax.add_patch(circle2))
    drs = []

    for c in circles:
        print(c.center[0])
        dr = DraggablePoint(c,-1)
        dr.connect()
        drs.append(dr)

    racun=polje(drs, X, Y)
    ax.quiver(X,Y,racun[0],racun[1], color='r',  alpha=0.5)
    ax.quiver(X,Y,racun[0],racun[1], edgecolor='k', facecolor='None', linewidth =.5) 
    plt.show    ()  

Answer 1

我也是新来的，所以我会尽力提供帮助。

对我来说合乎逻辑的解决方案是为您的圈子提供索引。每当您移动一个圆圈时，您的班级就会调用函数button_release_event 与您拥有的圆圈一样多。所以，当涉及到最后一个圆圈（带有你给它的特定索引）时，你只需要删除你的情节，然后重新做一遍（你需要画圆圈和字段）。

有趣的是，当它检查圆圈时，它总是会在第一个完成，索引为 0。我不知道为什么会这样，但这很好，因为它与你的图表上有多少个圆圈无关.

另外，您需要有self.c_kruznice = self.point.center[0], self.point.center[1] 行，因为它会更新您拖动的点的中心，以便它可以计算字段。关键部分：使用plt.draw() 绘制字段，因为只有在拖动圆圈后它才会更新您的字段。因为plt.show() 等你完成所有事情来绘制它（这就是为什么它会在你开始下一次拖动时绘制），但plt.draw() 在发布时就这样做了。

编辑：您需要在重新绘制之前清除列表circles（我编辑了代码）。

这是有这个想法的代码。

from pylab import *
from scipy import *
import matplotlib.pyplot as plt
import matplotlib.patches as patches
import scipy.constants as const

skr = const.pi*const.epsilon_0*4

class DraggablePoint:
    global Polje
    def __init__(self, p, q0, ind):
        self.q = q0
        self.point = p
        self.c_kruznice = p.center
        self.press = None
        self.indeks = ind

    def connect(self):
        self.cidpress = self.point.figure.canvas.mpl_connect('button_press_event', self.button_press_event)
        self.cidrelease = self.point.figure.canvas.mpl_connect('button_release_event',self.button_release_event)  
        self.cidmotion = self.point.figure.canvas.mpl_connect('motion_notify_event', self.motion_notify_event)  

    def disconnect(self):
        self.point.figure.canvas.mpl_disconnect(self.cidpress)
        self.point.figure.canvas.mpl_disconnect(self.cidrelease)
        self.point.figure.canvas.mpl_disconnect(self.cidmotion)

    def button_press_event(self,event):
        if event.inaxes != self.point.axes:
            return
        contains = self.point.contains(event)[0]
        if not contains: return
        self.press = self.point.center, event.xdata, event.ydata

    def button_release_event(self,event):
        self.press = None
        self.point.figure.canvas.draw()
        # This is the part which will erase field
        # and draw for us new one
        self.c_kruznice = self.point.center[0], self.point.center[1]
        if self.indeks == 0:
            racun = polje(drs, X, Y)
            ax.cla()
            circles = []
            circles.append(ax.add_patch(circle1))
            circles.append(ax.add_patch(circle))
            circles.append(ax.add_patch(circle2))
            circles.append(ax.add_patch(circle3))
            ax.quiver(X,Y,racun[0],racun[1], color='r',  alpha=0.5)
            ax.quiver(X,Y,racun[0],racun[1], edgecolor='k', facecolor='None', linewidth =.5)
            plt.draw()

    def motion_notify_event(self, event):
        if self.press is None: return
        if event.inaxes != self.point.axes: returnO
        self.point.center, xpress, ypress = self.press
        dx = event.xdata - xpress
        dy = event.ydata - ypress
        self.point.center = (self.point.center[0]+dx, self.point.center[1]+dy)
        self.point.figure.canvas.draw()


if __name__ == '__main__':
    f_s=0.3
    def R(x,y):
        r=np.sqrt(x**2+y**2)+f_s
        return r

    def polje(tela, X, Y):
        Ex = 0
        Ey = 0
        for i in range(len(tela)):
            r = R(tela[i].c_kruznice[0] - X, tela[i].c_kruznice[1] - Y )
            ex = X - tela[i].c_kruznice[0]
            ey = Y - tela[i].c_kruznice[1]
            Ex += (tela[i].q/skr)*(1/(r+f_s)**3)*ex
            Ey += (tela[i].q/skr)*(1/(r+f_s)**3)*ey
        return Ex, Ey


    fig = plt.figure(figsize=(8,8))
    ax = fig.add_axes([0.05,0.05,0.92,0.92])
    ax.set_xlim(-6,6)
    ax.set_ylim(-6,6)
    scale = 0.2
    X,Y=np.mgrid[-5:5:scale, -5:5:scale]

    circles = []
    q=3*const.e
    s=abs(q)
    sx=sqrt(s/np.pi)*1e8*5
    circle2 = patches.Circle((2,3), 0.3, fc='r', alpha=0.5, picker=True)
    circle1 = patches.Circle((2,-3), 0.3, fc='r', alpha=0.5, picker=True)
    circle = patches.Circle((-2,3), 0.3, fc='b', alpha=0.5, picker=True)
    circle3 = patches.Circle((-2,-3), 0.3, fc = 'b', alpha = 0.5, picker = True )
    circles.append(ax.add_patch(circle1))
    circles.append(ax.add_patch(circle))
    circles.append(ax.add_patch(circle2))
    circles.append(ax.add_patch(circle3))
    drs = []

    i = 0
    q = [-1, 1, -1, 1]
    for c in circles:
        dr = DraggablePoint(c, q[i], i)
        dr.connect()
        drs.append(dr)
        i += 1

    racun = polje(drs, X, Y)
    ax.quiver(X,Y,racun[0],racun[1], color='r',  alpha=0.5)
    ax.quiver(X,Y,racun[0],racun[1], edgecolor='k', facecolor='None', linewidth =.5)
    plt.show()