我正在尝试使粒子在Python中相互吸引。有点用，但是它们总是移到左上角（0; 0）。
一年前，CodeParade发布了video about a game of life he made with particles。我认为它很棒，并想用Python自己重新创建它。并不是那么困难，但是我有一个问题。每当一些粒子足够接近以相互吸引时，它们会稍微靠近一些，但同时它们“跑”到左上角（恰好是（0; 0））。我最初以为我没有正确应用吸引效果，但是在多次重读之后，我没有发现任何错误。有人知道为什么它不能按预期工作吗？
/这是代码/
#!/usr/bin/env python
# -*- coding: utf-8 -*-
import pygame, random, time
import numpy as np
attraction = [ [-2.6,8.8,10.2,0.7],
[4.1,-3.3,-3.1,4.4],
[0.6,3.7,-0.4,5.1],
[-7.8,0.3,0.3,0.0]]
minR = [[100.0,100.0,100.0,100.0],
[100.0,100.0,100.0,100.0],
[100.0,100.0,100.0,100.0],
[100.0,100.0,100.0,100.0]]
maxR = [[41.7,16.4,22.1,15.0],
[16.4,41.7,32.0,75.1],
[22.1,32.0,55.7,69.9],
[15.0,75.1,69.9,39.5]]
colors = [ (200,50,50),
(200,100,200),
(100,255,100),
(50,100,100)]
#Rouge
#Violet
#Vert
#Cyan
particles = []
#Number of particles
numberParticles = 5
#Width
w = 500
#Height
h = 500
#Radius of particles
r = 4
#Rendering speed
speed = 0.05
#Attraction speed factor
speedFactor = 0.01
#Min distance factor
minRFactor = 0.1
#Max distance factor
maxRFactor = 2
#Attraction factor
attractionFactor = 0.01
def distance(ax, ay, bx, by):
return intg((ax - bx)**2 + (ay - by)**2)
def intg(x):
return int(round(x))
def display(plan):
#Fill with black
#Momentarily moved to main
#pygame.Surface.fill(plan,(0,0,0))
#For each particle, draw it
for particle in particles:
pygame.draw.circle(plan,colors[particle[0]],(particle[1],particle[2]),r)
#Update display
pygame.display.flip()
def update(particles):
newParticles = []
for particleIndex in xrange(len(particles)):
typeId, x, y = particles[particleIndex]
othersX = [[],[],[],[]]
othersY = [[],[],[],[]]
#For every other particles
for otherParticle in particles[0:particleIndex]+particles[particleIndex+1:]:
otherTypeId, otherX, otherY = otherParticle
"""
#Draw minR and maxR of attraction for each color
pygame.draw.circle(screen,colors[otherTypeId],(x,y),intg(minR[typeId][otherTypeId] * minRFactor),1)
pygame.draw.circle(screen,colors[otherTypeId],(x,y),intg(maxR[typeId][otherTypeId] * maxRFactor),1)
"""
#If otherParticle is between minR and maxR from (x;y)
if (minR[typeId][otherTypeId] * minRFactor)**2 <= distance(x,y,otherX,otherY) <= (maxR[typeId][otherTypeId] * maxRFactor)**2:
#Append otherParticle's coordinates to othersX and othersY respectively
othersX[otherTypeId].append(otherX)
othersY[otherTypeId].append(otherY)
#Take the average attractions for each color
othersX = [np.mean(othersX[i]) * attraction[typeId][i] * attractionFactor for i in xrange(len(othersX)) if othersX[i] != []]
othersY = [np.mean(othersY[i]) * attraction[typeId][i] * attractionFactor for i in xrange(len(othersY)) if othersY[i] != []]
#If not attracted, stay in place
if othersX == []:
newX = x
else:
#Take the average attraction
avgX = np.mean(othersX)
#Determine the new x position
newX = x - (x - avgX) * speedFactor
#If out of screen, warp
if newX > w:
newX -= w
elif newX < 0:
newX += w
#If not attracted, stay in place
if othersY == []:
newY = y
else:
#Take the average attraction
avgY = np.mean(othersY)
#Determine the new y position
newY = y - (y - avgY) * speedFactor
#If out of screen, warp
if newY > h:
newY -= h
elif newY < 0:
newY += h
#Append updated particle to newParticles
newParticles.append([typeId,intg(newX),intg(newY)])
return newParticles
if __name__ == "__main__":
#Initialize pygame screen
pygame.init()
screen = pygame.display.set_mode([w,h])
#Particle = [type,posX,posY]
#Create randomly placed particles of random type
for x in xrange(numberParticles):
particles.append([random.randint(0,3),random.randint(0,w),random.randint(0,h)])
display(screen)
#Wait a bit
time.sleep(1)
while True:
#raw_input()
#Fill the screen with black
pygame.Surface.fill(screen,(0,0,0))
#Update particles
particles = update(particles)
#Display particles
display(screen)
#Wait a bit
time.sleep(speed)
答案 0 :(得分：3)
问题出在行中：
Set(tuple1)-Set(tuple2)
othersX = [np.mean(othersX[i]) * attraction[typeId][i] * attractionFactor for i in range(len(othersX)) if othersX[i] != []]
othersY = [np.mean(othersY[i]) * attraction[typeId][i] * attractionFactor for i in range(len(othersY)) if othersY[i] != []]
和othersX应该是位置，但是由于坐标乘以othersY，所以坐标会移到左上方。
通过忽略以下因素，可以轻松进行评估：
attraction[typeId][i] * attractionFactor一种选择是使用向量形式（othersX = [np.mean(othersX[i]) for i in range(len(othersX)) if othersX[i] != []]
othersY = [np.mean(othersY[i]) for i in range(len(othersY)) if othersY[i] != []]
，x）到（y，otherX）而不是位置：
otherY当然，您也必须适应新位置的计算：
for otherParticle in particles[0:particleIndex]+particles[particleIndex+1:]:
otherTypeId, otherX, otherY = otherParticle
if (minR[typeId][otherTypeId] * minRFactor)**2 <= distance(x,y,otherX,otherY) <= (maxR[typeId][otherTypeId] * maxRFactor)**2:
# Append otherParticle's coordinates to othersX and othersY respectively
othersX[otherTypeId].append(otherX - x)
othersY[otherTypeId].append(otherY - y)
othersX = [np.mean(othersX[i]) * attraction[typeId][i] * attractionFactor for i in range(len(othersX)) if othersX[i] != []]
othersY = [np.mean(othersY[i]) * attraction[typeId][i] * attractionFactor for i in range(len(othersY)) if othersY[i] != []]
avgX = np.mean(othersX)
newX = x + avgX * speedFactor
如另一个答案中所述，您应使用浮点数进行计算：
avgY = np.mean(othersY)
newY = y + avgY * speedFactor
def distance(ax, ay, bx, by):
# return intg((ax - bx)**2 + (ay - by)**2)
return (ax - bx)**2 + (ay - by)**2
但是在绘制圆时四舍五入为整数坐标
# newParticles.append([typeId,intg(newX),intg(newY)])
newParticles.append([typeId, newX, newY])
答案 1 :(得分：0)
可能是此行：
newParticles.append([typeId,intg(newX),intg(newY)])
您较早地计算了粒子的位置，但是intg()会将所有这些数字向下舍入为0，然后再将其保存到newparticles。随着时间的流逝，这会使事情朝[0,0]倾斜。
我要解决的方法是将particles和newparticles中的数据保留为浮点精度，仅在必须将内容显示在屏幕上时才进行舍入。这样一来，您使用的高精度就可以从一个时间步移到下一个时间步。