如何在 pygame 中检查鼠标与精灵的碰撞？

如何解决如何在 pygame 中检查鼠标与精灵的碰撞？

我用十字准线替换了我的鼠标，并且屏幕上有一些目标。当你射击一个目标时，它应该会从屏幕上消失。如何检查我的十字准线（我的实际鼠标）的 CENTER 是否与其中一个精灵发生碰撞？ 下面的代码并没有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，我不想要那样。

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,0.5)
target_group = pygame.sprite.Group()
while len(target_group)<10:
    target = Target(new_target_image,randrange(0,screen_width),screen_height))
    if pygame.sprite.spritecollide(target,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()

解决方法

由于目标是圆形的，可以通过计算鼠标指针到目标中心的距离来检测碰撞。

计算从鼠标光标到目标中心的 Euclidean distance (dx*dx + dy*dy) 的平方。测试距离的平方小于半径的平方：

将鼠标位置传递给 Crosshair.shoot。在检测到碰撞时遍历目标并kill一个目标：

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()。此函数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