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。

我当前的代码如下：

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，所以现在我把我的完整代码放在了一个部分，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 class Cell 。 将position设置为rect属性的中心，生成一个方向随机的向量：

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))

在方法update中更改 position。 将方向矢量dir和speed的乘积添加到 position ( pos )。 通过舍入（ round ）position 向量来更新矩形的 position：

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)

请参阅如何使用 Pygame 使球从墙上反弹？ 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)

参见Pygame 如何让球碰撞。 测试以查看单元格是否发生碰撞并在检测到碰撞时反映方向向量：

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)

另见碰撞和相交 - 圆和圆

---

完整示例：

import random
import pygame

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)

speed = [0.5, -0.5]

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  # 5
        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

        border_rect = pygame.Rect(0, 50, 400, 700)
        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) 

        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)

pygame.init()

screen = pygame.display.set_mode(SCREEN_SIZE)
pygame.display.set_caption("Covid-19 Simualtion")
all_cells = pygame.sprite.Group()  # PEP8: lower_case_name

for i in range(100):
    cell = Cell(GREEN1, 5, 10, 10)  # PEP8: lower_case_name
    all_cells.add(cell)

clock = pygame.time.Clock()

end = False
while not end:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            end = True
    all_cells.update()
    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