如何检查鼠标与 pygame 中精灵的碰撞？

Question

我用十字准线替换了鼠标，屏幕上有一些目标。 当你射击一个目标时，它应该从屏幕上消失。 如何检查我的十字准线（我的实际鼠标）的中心是否与其中一个精灵发生碰撞？ 下面的代码不能精确地检查我的十字准线的中心是否在一个目标上，所以即使你用十字准线中的空白区域射击它也会计数，我不希望这样。

import pygame
from random import randrange

class Crosshair(pygame.sprite.Sprite):
    def __init__(self, image):
        super().__init__()
        self.image = image
        self.rect = self.image.get_rect()
    def update(self):
        self.rect.center = pygame.mouse.get_pos()
    def shoot(self):
        pygame.sprite.spritecollide(self, target_group, True)

class Target(pygame.sprite.Sprite):
    def __init__(self, image, x, y):
        super().__init__()
        self.image = image
        self.rect = self.image.get_rect()
        self.rect.center = (x, y)

def set_background(background):
    (b_width, b_height) = background.get_size()
    for x in range(0, screen_width, b_width):
        for y in range(0, screen_height, b_height):
            screen.blit(background, (x, y))


#General setup
pygame.init()
fps = 60
clock = pygame.time.Clock()

#Background picture
background = pygame.image.load('Art/bg.png')

#Hide mouse
pygame.mouse.set_visible(False)

#Game Screen
screen_width = 1024
screen_height = 576
screen = pygame.display.set_mode((screen_width, screen_height))


#Crosshair
crosshair_image = pygame.image.load('Art/crosshair.png')
crosshair = Crosshair(crosshair_image)
crosshair_group = pygame.sprite.Group()
crosshair_group.add(crosshair)

#Targets
targets = 10
target_image = pygame.image.load('Art/target.png')
new_target_image = pygame.transform.rotozoom(target_image, 0, 0.5)
target_group = pygame.sprite.Group()
while len(target_group)<10:
    target = Target(new_target_image,
        randrange(0, screen_width),
        randrange(0, screen_height))
    if pygame.sprite.spritecollide(target, target_group, False):
        continue
    target_group.add(target)


running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        if event.type == pygame.MOUSEBUTTONDOWN:
            crosshair.shoot()

    set_background(background)

    target_group.draw(screen)

    crosshair_group.update()
    crosshair_group.draw(screen)
    
    pygame.display.flip()
    clock.tick(fps)

pygame.quit()

Answer 1

由于目标是圆形的，因此可以通过计算鼠标指针到目标中心的距离来检测碰撞。

计算从鼠标 cursor 到目标中心的欧几里得距离( dx*dx + dy*dy ) 的平方。 测试距离的平方小于半径的平方：

将鼠标 position 传递给Crosshair.shoot 。 Go 通过目标并在检测到碰撞时kill目标：

class Crosshair(pygame.sprite.Sprite):
    # [...]
    
    def shoot(self, mouse_pos):
        for target in target_group:
            dx = target.rect.centerx - mouse_pos[0]
            dy = target.rect.centery - mouse_pos[1]
            dist_sq = dx*dx + dy*dy
            radius = target.image.get_width() / 2
            if dist_sq < radius*radius:
                target.kill()

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        if event.type == pygame.MOUSEBUTTONDOWN:
            crosshair.shoot(event.pos)            # <--- pass event.pos

    # [...]

---

然而，更优雅的解决方案是使用pygame.sprite.collide_circle() 。 这个 function 可以作为回调参数传递给pygame.sprite.spritecollide() 。
对于此解决方案， pygame.sprite.Sprite对象必须具有属性radius ：

class Crosshair(pygame.sprite.Sprite):
    def __init__(self, image):
        super().__init__()
        self.image = image
        self.rect = self.image.get_rect()
        self.radius = 1

    def update(self):
        self.rect.center = pygame.mouse.get_pos()
    
    def shoot(self, mouse_pos):
        self.rect.center = mouse_pos
        pygame.sprite.spritecollide(self, target_group, True, pygame.sprite.collide_circle)

class Target(pygame.sprite.Sprite):
    def __init__(self, image, x, y):
        super().__init__()
        self.image = image
        self.rect = self.image.get_rect()
        self.rect.center = (x, y)
        self.radius = self.rect.width // 2