pygame中的随机系统运动

Question

我正在制作一个 Covid 模拟器，需要我的球随机移动。但是，我希望他们保持在选择的第一个随机方向上移动，并且只有在撞到另一个单元格或撞到墙上时才改变方向。

我目前的代码如下：

import random
import pygame

# --- constants --- (UPPER_CASE_NAMES)

GREEN1 = (0, 255, 0)  # Healthy cells
RED = (255, 0, 0)  # Infected cells
GREEN2 = (0, 100, 0)  # Healthy cells not susecptible
BLACK = (0, 0, 0)  # Dead cells
WHITE = (255, 255, 255)

BACKGROUND_COLOR = (225, 198, 153)

SCREEN_SIZE = (800, 800)


# --- classes --- (CamelCaseNames)

# class keeep only one cell so it should has name `Cell` instead of `Cells`

class Cell(pygame.sprite.Sprite):

    def __init__(self, color, speed, width, height):
        super().__init__()

        self.color = color
        self.speed = speed

        self.image = pygame.Surface([width, height])
        self.image.fill(WHITE)
        self.image.set_colorkey(WHITE)

        self.radius = width // 2  # 25
        center = [width // 2, height // 2]
        pygame.draw.circle(self.image, self.color, center, self.radius, width=0)

        self.rect = self.image.get_rect()
        self.rect.x = random.randint(0, 400)
        self.rect.y = random.randint(50, 700)

        self.pos = pygame.math.Vector2(self.rect.center)
        self.dir = pygame.math.Vector2(1, 0).rotate(random.randrange(360))

    def update(self):
        self.pos += self.dir * self.speed

        if self.pos.x - self.radius < 0 or self.pos.x + self.radius > SCREEN_SIZE[0]:
            self.dir.x *= -1
        if self.pos.y - self.radius < 0 or self.pos.y + self.radius > SCREEN_SIZE[1]:
            self.dir.y *= -1

        for other_cell in all_cells:
            if all_cells != self:
                distance_vec = self.pos - other_cell.pos
                if 0 < distance_vec.length_squared() < (self.radius * 2) ** 2:
                    self.dir.reflect_ip(distance_vec)
                    other_cell.dir.reflect_ip(distance_vec)

        self.rect.centerx = round(self.pos.x)
        self.rect.centery = round(self.pos.y)


# --- functions --- (lower_case_names)

# empty

# --- main --- (lower_case_names)

pygame.init()

screen = pygame.display.set_mode(SCREEN_SIZE)
pygame.display.set_caption("Covid-19 Simualtion")

speed = [0.5, -0.5]

# - objects -

all_cells = pygame.sprite.Group()  # PEP8: lower_case_name

for _ in range(5):
    cell = Cell(GREEN1, 5, 10, 10)  # PEP8: lower_case_name
    all_cells.add(cell)

# - loop -

clock = pygame.time.Clock()

end = False
while not end:

    # - events -

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            end = True

    # - upadates (without draws) -

    all_cells.update()

    # - draws (without updates) -

    screen.fill(BACKGROUND_COLOR)
    pygame.draw.rect(screen, BLACK, (0, 50, 400, 700), 3)

    all_cells.draw(screen)

    pygame.display.flip()
    clock.tick(30)  # to use less CPU

# - end

pygame.quit()  # some system may need it to close window

我想知道是否有办法做到这一点，非常感谢任何帮助。提前致谢。我尝试将下面的第一个答案复制到我的 pycharm 中，但它没有用，所以现在我已经把我的完整代码放在了上面，而不是一个部分，以备不时之需。很抱歉没有把它全部放在前面

Answer 1

我建议使用pygame.math.Vector2。将属性pos 和dir（位置和方向）添加到类Cell。以rect属性的中心设置位置，生成方向随机的向量：

class Cell(pygame.sprite.Sprite):
    def __init__(self, color, speed, width, height):
        # [...]

        self.pos = pygame.math.Vector2(self.rect.center)
        self.dir = pygame.math.Vector2(1, 0).rotate(random.randrange(360))

更改方法update 中的位置。将方向向量dir 和speed 的乘积添加到位置（pos）。通过舍入 (round) 位置向量来更新矩形的位置：

class Cell(pygame.sprite.Sprite):
    # [...]

    def update(self):
        self.pos += self.dir * self.speed
        self.rect.centerx = round(self.pos.x)
        self.rect.centery = round(self.pos.y)

查看How to make ball bounce off wall with Pygame? 并将建议应用于您的代码：

class Cell(pygame.sprite.Sprite):
    # [...]

    def update(self):
        self.pos += self.dir * self.speed

        if self.pos.x - self.radius < 0:
            self.pos.x = self.radius
            self.dir.x = abs(self.dir.x)
        elif self.pos.x + self.radius > 400:
            self.pos.x = 400 - self.radius
            self.dir.x = -abs(self.dir.x)
        if self.pos.y - self.radius < 50:
            self.pos.y = 50 + self.radius
            self.dir.y = abs(self.dir.y)
        elif self.pos.y + self.radius > 700:
            self.pos.y = 700 - self.radius
            self.dir.y = -abs(self.dir.y) 

        self.rect.centerx = round(self.pos.x)
        self.rect.centery = round(self.pos.y)

见Pygame how to let balls collide。测试检测到碰撞时单元格是否发生碰撞并反射方向向量：

class Cell(pygame.sprite.Sprite):
    # [...]

    def update(self):
        self.pos += self.dir * self.speed

        # [...] 

        for other_cell in all_cells:
            if all_cells != self:
                distance_vec = self.pos - other_cell.pos
                if 0 < distance_vec.length_squared() < (self.radius*2) ** 2:
                    self.dir.reflect_ip(distance_vec)
                    other_cell.dir.reflect_ip(distance_vec)

        self.rect.centerx = round(self.pos.x)
        self.rect.centery = round(self.pos.y)

另见Collision and Intersection - Circle and circle

---

完整示例：

import random
import pygame

class Particle(pygame.sprite.Sprite):
    def __init__(self, hue, pos, radius, dir, vel):
        super().__init__()
        self.pos = pygame.math.Vector2(pos)
        self.dir = pygame.math.Vector2(dir)
        self.vel = vel
        self.radius = radius
        self.rect = pygame.Rect(round(self.pos.x - radius), round(self.pos.y - radius), radius*2, radius*2)
        self.image = pygame.Surface((radius*2, radius*2))
        self.changeColor(hue)

    def changeColor(self, hue):
        self.hue = hue
        color = pygame.Color(0)
        color.hsla = (self.hue, 100, 50, 100)
        self.image.set_colorkey((0, 0, 0))
        self.image.fill(0)
        pygame.draw.circle(self.image, color, (self.radius, self.radius), self.radius)

    def move(self):
        self.pos += self.dir * self.vel

    def update(self, border_rect):

        if self.pos.x - self.radius < border_rect.left:
            self.pos.x = border_rect.left + self.radius
            self.dir.x = abs(self.dir.x)
        elif self.pos.x + self.radius > border_rect.right:
            self.pos.x = border_rect.right - self.radius
            self.dir.x = -abs(self.dir.x)
        if self.pos.y - self.radius < border_rect.top:
            self.pos.y = border_rect.top + self.radius
            self.dir.y = abs(self.dir.y)
        elif self.pos.y + self.radius > border_rect.bottom:
            self.pos.y = border_rect.bottom - self.radius
            self.dir.y = -abs(self.dir.y) 

        self.rect = self.image.get_rect(center = (round(self.pos.x), round(self.pos.y)))

pygame.init()
window = pygame.display.set_mode((400, 400))
clock = pygame.time.Clock()
rect_area = window.get_rect().inflate(-40, -40)

all_particles = pygame.sprite.Group()
radius, velocity = 5, 1
pos_rect = rect_area.inflate(-radius * 2, -radius * 2)

run = True
while run:
    clock.tick(40)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False

    if len(all_particles.sprites()) < 100:
        hue = random.randrange(360)
        x = random.randrange(pos_rect.left, pos_rect.right)
        y = random.randrange(pos_rect.top, pos_rect.bottom)
        dir = pygame.math.Vector2(1, 0).rotate(random.randrange(360))
        particle = Particle(hue, (x, y), radius, dir, velocity)
        if not pygame.sprite.spritecollide(particle, all_particles, False, collided = pygame.sprite.collide_circle):
            all_particles.add(particle)

    for particle in all_particles:
        particle.move()

    particle_list = all_particles.sprites()
    for i, particle_1 in enumerate(particle_list):
        for particle_2 in particle_list[i:]:
            distance_vec = particle_1.pos - particle_2.pos
            if 0 < distance_vec.length_squared() < (particle_1.radius + particle_2.radius) ** 2:
                particle_1.dir.reflect_ip(distance_vec)
                particle_2.dir.reflect_ip(distance_vec)
                if abs(particle_1.hue - particle_2.hue) <= 180:
                    hue = (particle_1.hue + particle_2.hue) // 2
                else:
                    hue = (particle_1.hue + particle_2.hue + 360) // 2 % 360
                particle_1.changeColor(hue)
                particle_2.changeColor(hue)
                break

    all_particles.update(rect_area)

    window.fill(0)
    pygame.draw.rect(window, (255, 0, 0), rect_area, 3)
    all_particles.draw(window)
    pygame.display.flip()

pygame.quit()
exit()