意外粒子模拟行为

Question

在基本粒子模拟器上工作，其中规则可以应用于粒子组(例如。红色吸引蓝色，蓝色排斥黄色等)。使用这段视频作为指导，我创建了一个简单的python应用程序，它可以工作，但是粒子的行为并不像预期的那样。下面的代码是一个例子，蓝色粒子开始被红色粒子吸引，但不是振荡，而是从红色粒子上反弹而变得混沌。

import pygame
import random

class Particle():
    def __init__(self, x, y, mass, color):
        self.x = x
        self.y = y
        self.xvel = 0
        self.yvel = 0
        self.mass = mass
        self.color = color

def main():
    random.seed(1662443792)

    # initialize screen
    pygame.init()
    width = 1000
    height = 800
    screen = pygame.display.set_mode((width, height))
    clock = pygame.time.Clock()
    running = True

    # spawn some particles
    blue = []
    for i in range(1):
        x = random.randint(0, width)
        y = random.randint(0, height)
        p = Particle(x, y, 1, (0, 0, 255))
        blue.append(p)
    red = []
    for i in range(1):
        x = random.randint(0, width)
        y = random.randint(0, height)
        p = Particle(x, y, 10, (255, 0, 0))
        red.append(p)

    while running:
        pygame.display.flip()
        screen.fill((0, 0, 0))
        draw_particles(screen, blue)
        draw_particles(screen, red)
        rule(blue, red, -1)
        clock.tick(144)

        # quit simulation
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                return
            elif event.type == pygame.KEYDOWN and event.key == pygame.K_ESCAPE:
                pygame.quit()

# PHYSICS FOR PARTICLES DONE HERE               
def rule(set1, set2, g):
    for a in set1:
        fx = 0
        fy = 0
        for b in set2:
            # calculate distance between particles
            dx = a.x - b.x
            dy = a.y - b.y
            d = (dx * dx + dy * dy) ** .5
            if (d > 0):
                # calculate force between particles
                force = (g * a.mass * b.mass) / (d*d)
                fx += force * dx
                fy += force * dy
        # update force and position
        a.xvel = (a.xvel + fx)
        a.yvel =  (a.yvel + fy)
        a.x += a.xvel
        a.y += a.yvel
        # if particle wants to leave screen, flip velocity
        if (a.x >= 1000 or a.x <= 0):
            a.xvel *= -1
        if (a.y >= 800 or a.y <= 0):
            a.yvel *= -1

def draw_particles(screen, particle_set1):
    for p in particle_set1:
        pygame.draw.circle(screen, p.color, (p.x, p.y), 5, 2)

if __name__ == '__main__':
    main()

Answer 1

我相信你对力的估计是不恰当的。你把它乘以dx，我想得到力的“方向”，但是你应该除以d。

另外，关于你的速度和位置更新，我认为你高估了两者的变化，而不是a.xvel += fx，我会期望a.xvel += fx*dt，用dt你的集成步骤，这里我猜是0.144s。