Pygame中基于像素的形状碰撞检测：理解与高效实践

import pygame

# 假设 SURFACE 已经初始化
# SURFACE = pygame.display.set_mode((800, 600)) 

circle_color = (0, 255, 0)
polygon_color = (255, 0, 0)

# 假设已经绘制了图形
# pygame.draw.circle(SURFACE, circle_color, (100, 100), 50)
# pygame.draw.polygon(SURFACE, polygon_color, [(200, 100), (250, 150), (150, 150)])

circle_mask = pygame.mask.from_threshold(SURFACE, circle_color)
polygon_mask = pygame.mask.from_threshold(SURFACE, polygon_color)

if circle_mask.overlap(polygon_mask, offset=(0,0)):
   print("collision")

if object1.rect.colliderect(object2.rect):
    # 只有当边界框重叠时，才进行像素级检测
    # ...

import pygame

# 初始化Pygame
pygame.init()
screen_width = 800
screen_height = 600
screen = pygame.display.set_mode((screen_width, screen_height))
pygame.display.set_caption("Pygame Mask Collision Demo")

# 颜色定义
GREEN = (0, 255, 0)
RED = (255, 0, 0)
WHITE = (255, 255, 255)
BLACK = (0, 0, 0)

class CollidableShape:
    """
    表示一个可碰撞的形状对象，包含其自身的表面、矩形和掩码。
    """
    def __init__(self, color, position, size, shape_type="circle"):
        self.color = color
        self.position = list(position) # [x, y]
        self.size = size
        self.shape_type = shape_type
        # 创建一个带有透明通道的Surface，大小足够容纳形状
        self.surface = pygame.Surface((size * 2, size * 2), pygame.SRCALPHA) 
        self.rect = self.surface.get_rect(center=self.position)
        self.mask = None
        self._create_shape_and_mask()

    def _create_shape_and_mask(self):
        """在对象的独立Surface上绘制形状并生成掩码。"""
        self.surface.fill((0, 0, 0, 0)) # 清空Surface，保持透明

        # 在对象的局部坐标系中绘制形状
        if self.shape_type == "circle":
            pygame.draw.circle(self.surface, self.color, (self.size, self.size), self.size)
        elif self.shape_type == "polygon":
            # 示例：一个等边三角形
            points = [
                (self.size, self.size - self.size), 
                (self.size + self.size * 0.866, self.size + self.size * 0.5), 
                (self.size - self.size * 0.866, self.size + self.size * 0.5) 
            ]
            pygame.draw.polygon(self.surface, self.color, points)

        # 从这个独立的Surface生成掩码
        self.mask = pygame.mask.from_surface(self.surface)

    def update(self, dx, dy):
        """更新对象位置。"""
        self.position[0] += dx
        self.position[1] += dy
        self.rect.center = self.position

    def draw(self, screen_surface):
        """将对象绘制到主屏幕表面。"""
        screen_surface.blit(self.surface, self.rect)

    def check_collision(self, other_shape):
        """
        检查与另一个CollidableShape对象的碰撞。
        先进行边界框检测，再进行像素级掩码检测。
        """
        # 步骤1：边界框碰撞检测 (快速筛选)
        if not self.rect.colliderect(other_shape.rect):
            return False

        # 步骤2：像素级掩码碰撞检测 (精确检测)
        # 计算 other_shape 的掩码相对于 self 的掩码的偏移量
        offset_x = other_shape.rect.x - self.rect.x
        offset_y = other_shape.rect.y - self.rect.y

        # 如果掩码在给定偏移量下有任何重叠，则返回True
        return self.mask.overlap(other_shape.mask, (offset_x, offset_y)) is not None

# 创建可碰撞的形状实例
circle = CollidableShape(GREEN, (200, 300), 50, "circle")
polygon = CollidableShape(RED, (400, 300), 60, "polygon")

# 游戏循环
running = True
clock = pygame.time.Clock()
dx_circle, dy_circle = 2, 0
dx_polygon, dy_polygon = -1, 0

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

    # 更新形状位置
    circle.update(dx_circle, dy_circle)
    polygon.update(dx_polygon, dy_polygon)

    # 边界反弹
    if not screen.get_rect().colliderect(circle.rect):
        dx_circle *= -1
    if not screen.get_rect().colliderect(polygon.rect):
        dx_polygon *= -1

    # 碰撞检测
    collision_detected = circle.check_collision(polygon)

    # 绘制
    screen.fill(BLACK)
    circle.draw(screen)
    polygon.draw(screen)

    # 显示碰撞状态
    font = pygame.font.Font(None, 36)
    text = font.render(f"Collision: {collision_detected}", True, WHITE)
    screen.blit(text, (10, 10))

    pygame.display.flip()
    clock.tick(60)

pygame.quit()