Detecting the point of collision with Pygame

Question

I am making a game with Pygame. For this game I need to be able to detect not only that two rectangles have collided, but also the point of collision between them. I looked at the documentation but couldn't seem to find any answers.

Is something like this possible?

sloth sloth · Accepted Answer · 2019-03-29T07:01:22

You can use Rect.clip:

crops a rectangle inside another

clip(Rect) -> Rect

Returns a new rectangle that is cropped to be completely inside the argument Rect. If the two rectangles do not overlap to begin with, a Rect with 0 size is returned.

Here's an example:

import pygame
import random

class Stuff(pygame.sprite.Sprite):
    def __init__(self, pos, color, *args):
        super().__init__(*args)
        self.image = pygame.Surface((30, 30))
        self.image.fill(color)
        self.rect = self.image.get_rect(center=pos)
        self.pos = pygame.Vector2(pos)

    def update(self):
        self.rect.center = self.pos

def main():
    pygame.init()
    screen = pygame.display.set_mode((500, 500))
    screen_rect = screen.get_rect()
    font = pygame.font.SysFont(None, 26)
    clock = pygame.time.Clock()
    sprites = pygame.sprite.Group()
    blocks = pygame.sprite.Group()

    movement = {
        pygame.K_UP:    ( 0, -1),
        pygame.K_DOWN:  ( 0,  1),
        pygame.K_LEFT:  (-1,  0),
        pygame.K_RIGHT: ( 1,  0)
    }

    for _ in range(15):
        x, y = random.randint(0, 500), random.randint(0, 500)
        color = random.choice(['green', 'yellow'])
        Stuff((x, y), pygame.Color(color), sprites, blocks)

    player = Stuff(screen_rect.center, pygame.Color('dodgerblue'))
    sprites.add(player)

    dt = 0
    while True:
        events = pygame.event.get()
        for e in events:
            if e.type == pygame.QUIT:
                return

        pressed = pygame.key.get_pressed()
        move = pygame.Vector2()
        for dir in (movement[key] for key in movement if pressed[key]):
            move += dir
        if move.length() > 0: move.normalize_ip()
        player.pos += move * dt/5

        sprites.update()
        screen.fill(pygame.Color('black'))
        sprites.draw(screen)

        for block in pygame.sprite.spritecollide(player, blocks, False):
            clip = player.rect.clip(block.rect)
            pygame.draw.rect(screen, pygame.Color('red'), clip)
            hits = [edge for edge in ['bottom', 'top', 'left', 'right'] if getattr(clip, edge) == getattr(player.rect, edge)]
            text = font.render(f'Collision at {", ".join(hits)}', True, pygame.Color('white'))
            screen.blit(text, (20, 20))

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

if __name__ == '__main__':
    main()

Detecting the point of collision with Pygame

1 Answers