使用Python的Matplotlib三维散点图动画不会出错，但它不会工作

Question

我正试图编写一个N-body simulation，但在Matplotlib的动画功能方面遇到了一些障碍。我不完全确定如何更新散点图中的数据，所以我认为这可能是问题所在。在

import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
import matplotlib.animation as animation
system = []
xlist = []
ylist = []
zlist = []
poslist = []
nbodies = 3
scale = 100
mass = 0
timestep = 0.1
step = 0.01
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
i = 1
plt.ion()
scat = ax.scatter(xlist, ylist, zlist, c='r', marker='o', animated=True)
class Body:
    def __init__(self, posvel, mass):
        self.state = np.zeros((3, 3))
        self.state[0:2] = posvel * scale
        self.state[2] = np.array([0.0, 0.0, 0.0])
        self.mass = mass
    def setPos(self, pos):
        self.state[0] = pos
    def setVel(self, vel):
        self.state[1] = vel
    def setAcc(self, acc):
        self.state[2] = acc
    def getPos(self):
        return self.state[0]
    def getVel(self):
        return self.state[1]
    def getAcc(self):
        return self.state[2]
def startSystem():
    for i in range(0,nbodies):
        system.append(Body(np.random.rand(2,3), np.random.random_sample()))
        curpos = system[i].getPos()
        xlist.append(curpos[0])
        ylist.append(curpos[1])
        zlist.append(curpos[2])
def stepSystem():
    xlist = []
    ylist = []
    zlist = []
    poslist = []
    for i in range(0,nbodies):
        curpos = system[i].getPos()
        system[i].setPos(curpos + 1*step)
        poslist.append(curpos + 1*step)
        xlist.append(curpos[0] + 1*step)
        ylist.append(curpos[1] + 1*step)
        zlist.append(curpos[2] + 1*step)
    yield xlist, ylist, zlist
def simPoints(stepSystem):
    xlist, ylist,zlist = stepSystem[0], stepSystem[1], stepSystem[2]
    scat.set_offsets(poslist)
    return scat
def Plot():
    ani = animation.FuncAnimation(fig, simPoints, stepSystem, blit=False,\
     interval=100, repeat=True)
    plt.show()
def main():
    startSystem()
    Plot()